1 Writing Programs with NCURSES 2 3Writing Programs with NCURSES 4 5 by Eric S. Raymond and Zeyd M. Ben-Halim 6 updates since release 1.9.9e by Thomas Dickey 7 8Contents 9 10 * Introduction 11 + A Brief History of Curses 12 + Scope of This Document 13 + Terminology 14 * The Curses Library 15 + An Overview of Curses 16 o Compiling Programs using Curses 17 o Updating the Screen 18 o Standard Windows and Function Naming Conventions 19 o Variables 20 + Using the Library 21 o Starting up 22 o Output 23 o Input 24 o Using Forms Characters 25 o Character Attributes and Color 26 o Mouse Interfacing 27 o Finishing Up 28 + Function Descriptions 29 o Initialization and Wrapup 30 o Causing Output to the Terminal 31 o Low-Level Capability Access 32 o Debugging 33 + Hints, Tips, and Tricks 34 o Some Notes of Caution 35 o Temporarily Leaving ncurses Mode 36 o Using ncurses under xterm 37 o Handling Multiple Terminal Screens 38 o Testing for Terminal Capabilities 39 o Tuning for Speed 40 o Special Features of ncurses 41 + Compatibility with Older Versions 42 o Refresh of Overlapping Windows 43 o Background Erase 44 + XSI Curses Conformance 45 * The Panels Library 46 + Compiling With the Panels Library 47 + Overview of Panels 48 + Panels, Input, and the Standard Screen 49 + Hiding Panels 50 + Miscellaneous Other Facilities 51 * The Menu Library 52 + Compiling with the menu Library 53 + Overview of Menus 54 + Selecting items 55 + Menu Display 56 + Menu Windows 57 + Processing Menu Input 58 + Miscellaneous Other Features 59 * The Forms Library 60 + Compiling with the forms Library 61 + Overview of Forms 62 + Creating and Freeing Fields and Forms 63 + Fetching and Changing Field Attributes 64 o Fetching Size and Location Data 65 o Changing the Field Location 66 o The Justification Attribute 67 o Field Display Attributes 68 o Field Option Bits 69 o Field Status 70 o Field User Pointer 71 + Variable-Sized Fields 72 + Field Validation 73 o TYPE_ALPHA 74 o TYPE_ALNUM 75 o TYPE_ENUM 76 o TYPE_INTEGER 77 o TYPE_NUMERIC 78 o TYPE_REGEXP 79 + Direct Field Buffer Manipulation 80 + Attributes of Forms 81 + Control of Form Display 82 + Input Processing in the Forms Driver 83 o Page Navigation Requests 84 o Inter-Field Navigation Requests 85 o Intra-Field Navigation Requests 86 o Scrolling Requests 87 o Field Editing Requests 88 o Order Requests 89 o Application Commands 90 + Field Change Hooks 91 + Field Change Commands 92 + Form Options 93 + Custom Validation Types 94 o Union Types 95 o New Field Types 96 o Validation Function Arguments 97 o Order Functions For Custom Types 98 o Avoiding Problems 99 _________________________________________________________________ 100 101Introduction 102 103 This document is an introduction to programming with curses. It is not 104 an exhaustive reference for the curses Application Programming 105 Interface (API); that role is filled by the curses manual pages. 106 Rather, it is intended to help C programmers ease into using the 107 package. 108 109 This document is aimed at C applications programmers not yet 110 specifically familiar with ncurses. If you are already an experienced 111 curses programmer, you should nevertheless read the sections on Mouse 112 Interfacing, Debugging, Compatibility with Older Versions, and Hints, 113 Tips, and Tricks. These will bring you up to speed on the special 114 features and quirks of the ncurses implementation. If you are not so 115 experienced, keep reading. 116 117 The curses package is a subroutine library for terminal-independent 118 screen-painting and input-event handling which presents a high level 119 screen model to the programmer, hiding differences between terminal 120 types and doing automatic optimization of output to change one screen 121 full of text into another. Curses uses terminfo, which is a database 122 format that can describe the capabilities of thousands of different 123 terminals. 124 125 The curses API may seem something of an archaism on UNIX desktops 126 increasingly dominated by X, Motif, and Tcl/Tk. Nevertheless, UNIX 127 still supports tty lines and X supports xterm(1); the curses API has 128 the advantage of (a) back-portability to character-cell terminals, and 129 (b) simplicity. For an application that does not require bit-mapped 130 graphics and multiple fonts, an interface implementation using curses 131 will typically be a great deal simpler and less expensive than one 132 using an X toolkit. 133 134 A Brief History of Curses 135 136 Historically, the first ancestor of curses was the routines written to 137 provide screen-handling for the vi editor; these used the termcap 138 database facility (both released in 3BSD) for describing terminal 139 capabilities. These routines were abstracted into a documented library 140 and first released with the early BSD UNIX versions. All of this work 141 was done by students at the University of California (Berkeley 142 campus). The curses library was first published in 4.0BSD, a year 143 after 3BSD (i.e., late 1980). 144 145 After graduation, one of those students went to work at AT&T Bell 146 Labs, and made an improved termcap library called terminfo (i.e., 147 "libterm"), and adapted the curses library to use this. That was 148 subsequently released in System V Release 2 (early 1984). Thereafter, 149 other developers added to the curses and terminfo libraries. For 150 instance, a student at Cornell University wrote an improved terminfo 151 library as well as a tool (tic) to compile the terminal descriptions. 152 As a general rule, AT&T did not identify the developers in the 153 source-code or documentation; the tic and infocmp programs are the 154 exceptions. 155 156 System V Release 3 from Bell Labs featured a rewritten and 157 much-improved curses library, along with the tic program (late 1986). 158 159 To recap, terminfo is based on Berkeley's termcap database, but 160 contains a number of improvements and extensions. Parameterized 161 capabilities strings were introduced, making it possible to describe 162 multiple video attributes, and colors and to handle far more unusual 163 terminals than possible with termcap. In the later AT&T System V 164 releases, curses evolved to use more facilities and offer more 165 capabilities, going far beyond BSD curses in power and flexibility. 166 167 Scope of This Document 168 169 This document describes ncurses, a free implementation of the System V 170 curses API with some clearly marked extensions. It includes the 171 following System V curses features: 172 * Support for multiple screen highlights (BSD curses could only 173 handle one "standout" highlight, usually reverse-video). 174 * Support for line- and box-drawing using forms characters. 175 * Recognition of function keys on input. 176 * Color support. 177 * Support for pads (windows of larger than screen size on which the 178 screen or a subwindow defines a viewport). 179 180 Also, this package makes use of the insert and delete line and 181 character features of terminals so equipped, and determines how to 182 optimally use these features with no help from the programmer. It 183 allows arbitrary combinations of video attributes to be displayed, 184 even on terminals that leave "magic cookies" on the screen to mark 185 changes in attributes. 186 187 The ncurses package can also capture and use event reports from a 188 mouse in some environments (notably, xterm under the X window system). 189 This document includes tips for using the mouse. 190 191 The ncurses package was originated by Pavel Curtis. The original 192 maintainer of this package is Zeyd Ben-Halim <zmbenhal@netcom.com>. 193 Eric S. Raymond <esr@snark.thyrsus.com> wrote many of the new features 194 in versions after 1.8.1 and wrote most of this introduction. Juergen 195 Pfeifer wrote all of the menu and forms code as well as the Ada95 196 binding. Ongoing work is being done by Thomas Dickey (maintainer). 197 Contact the current maintainers at bug-ncurses@gnu.org. 198 199 This document also describes the panels extension library, similarly 200 modeled on the SVr4 panels facility. This library allows you to 201 associate backing store with each of a stack or deck of overlapping 202 windows, and provides operations for moving windows around in the 203 stack that change their visibility in the natural way (handling window 204 overlaps). 205 206 Finally, this document describes in detail the menus and forms 207 extension libraries, also cloned from System V, which support easy 208 construction and sequences of menus and fill-in forms. 209 210 Terminology 211 212 In this document, the following terminology is used with reasonable 213 consistency: 214 215 window 216 A data structure describing a sub-rectangle of the screen 217 (possibly the entire screen). You can write to a window as 218 though it were a miniature screen, scrolling independently of 219 other windows on the physical screen. 220 221 screens 222 A subset of windows which are as large as the terminal screen, 223 i.e., they start at the upper left hand corner and encompass 224 the lower right hand corner. One of these, stdscr, is 225 automatically provided for the programmer. 226 227 terminal screen 228 The package's idea of what the terminal display currently looks 229 like, i.e., what the user sees now. This is a special screen. 230 231The Curses Library 232 233 An Overview of Curses 234 235 Compiling Programs using Curses 236 237 In order to use the library, it is necessary to have certain types and 238 variables defined. Therefore, the programmer must have a line: 239 #include <curses.h> 240 241 at the top of the program source. The screen package uses the Standard 242 I/O library, so <curses.h> includes <stdio.h>. <curses.h> also 243 includes <termios.h>, <termio.h>, or <sgtty.h> depending on your 244 system. It is redundant (but harmless) for the programmer to do these 245 includes, too. In linking with curses you need to have -lncurses in 246 your LDFLAGS or on the command line. There is no need for any other 247 libraries. 248 249 Updating the Screen 250 251 In order to update the screen optimally, it is necessary for the 252 routines to know what the screen currently looks like and what the 253 programmer wants it to look like next. For this purpose, a data type 254 (structure) named WINDOW is defined which describes a window image to 255 the routines, including its starting position on the screen (the (y, 256 x) coordinates of the upper left hand corner) and its size. One of 257 these (called curscr, for current screen) is a screen image of what 258 the terminal currently looks like. Another screen (called stdscr, for 259 standard screen) is provided by default to make changes on. 260 261 A window is a purely internal representation. It is used to build and 262 store a potential image of a portion of the terminal. It does not bear 263 any necessary relation to what is really on the terminal screen; it is 264 more like a scratchpad or write buffer. 265 266 To make the section of physical screen corresponding to a window 267 reflect the contents of the window structure, the routine refresh() 268 (or wrefresh() if the window is not stdscr) is called. 269 270 A given physical screen section may be within the scope of any number 271 of overlapping windows. Also, changes can be made to windows in any 272 order, without regard to motion efficiency. Then, at will, the 273 programmer can effectively say "make it look like this," and let the 274 package implementation determine the most efficient way to repaint the 275 screen. 276 277 Standard Windows and Function Naming Conventions 278 279 As hinted above, the routines can use several windows, but two are 280 automatically given: curscr, which knows what the terminal looks like, 281 and stdscr, which is what the programmer wants the terminal to look 282 like next. The user should never actually access curscr directly. 283 Changes should be made to through the API, and then the routine 284 refresh() (or wrefresh()) called. 285 286 Many functions are defined to use stdscr as a default screen. For 287 example, to add a character to stdscr, one calls addch() with the 288 desired character as argument. To write to a different window. use the 289 routine waddch() (for window-specific addch()) is provided. This 290 convention of prepending function names with a "w" when they are to be 291 applied to specific windows is consistent. The only routines which do 292 not follow it are those for which a window must always be specified. 293 294 In order to move the current (y, x) coordinates from one point to 295 another, the routines move() and wmove() are provided. However, it is 296 often desirable to first move and then perform some I/O operation. In 297 order to avoid clumsiness, most I/O routines can be preceded by the 298 prefix "mv" and the desired (y, x) coordinates prepended to the 299 arguments to the function. For example, the calls 300 move(y, x); 301 addch(ch); 302 303 can be replaced by 304 mvaddch(y, x, ch); 305 306 and 307 wmove(win, y, x); 308 waddch(win, ch); 309 310 can be replaced by 311 mvwaddch(win, y, x, ch); 312 313 Note that the window description pointer (win) comes before the added 314 (y, x) coordinates. If a function requires a window pointer, it is 315 always the first parameter passed. 316 317 Variables 318 319 The curses library sets some variables describing the terminal 320 capabilities. 321 type name description 322 ------------------------------------------------------------------ 323 int LINES number of lines on the terminal 324 int COLS number of columns on the terminal 325 326 The curses.h also introduces some #define constants and types of 327 general usefulness: 328 329 bool 330 boolean type, actually a "char" (e.g., bool doneit;) 331 332 TRUE 333 boolean "true" flag (1). 334 335 FALSE 336 boolean "false" flag (0). 337 338 ERR 339 error flag returned by routines on a failure (-1). 340 341 OK 342 error flag returned by routines when things go right. 343 344 Using the Library 345 346 Now we describe how to actually use the screen package. In it, we 347 assume all updating, reading, etc. is applied to stdscr. These 348 instructions will work on any window, providing you change the 349 function names and parameters as mentioned above. 350 351 Here is a sample program to motivate the discussion: 352#include <stdlib.h> 353#include <curses.h> 354#include <signal.h> 355 356static void finish(int sig); 357 358int 359main(int argc, char *argv[]) 360{ 361 int num = 0; 362 363 /* initialize your non-curses data structures here */ 364 365 (void) signal(SIGINT, finish); /* arrange interrupts to terminate */ 366 367 (void) initscr(); /* initialize the curses library */ 368 keypad(stdscr, TRUE); /* enable keyboard mapping */ 369 (void) nonl(); /* tell curses not to do NL->CR/NL on output */ 370 (void) cbreak(); /* take input chars one at a time, no wait for \n */ 371 (void) echo(); /* echo input - in color */ 372 373 if (has_colors()) 374 { 375 start_color(); 376 377 /* 378 * Simple color assignment, often all we need. Color pair 0 cannot 379 * be redefined. This example uses the same value for the color 380 * pair as for the foreground color, though of course that is not 381 * necessary: 382 */ 383 init_pair(1, COLOR_RED, COLOR_BLACK); 384 init_pair(2, COLOR_GREEN, COLOR_BLACK); 385 init_pair(3, COLOR_YELLOW, COLOR_BLACK); 386 init_pair(4, COLOR_BLUE, COLOR_BLACK); 387 init_pair(5, COLOR_CYAN, COLOR_BLACK); 388 init_pair(6, COLOR_MAGENTA, COLOR_BLACK); 389 init_pair(7, COLOR_WHITE, COLOR_BLACK); 390 } 391 392 for (;;) 393 { 394 int c = getch(); /* refresh, accept single keystroke of input */ 395 attrset(COLOR_PAIR(num % 8)); 396 num++; 397 398 /* process the command keystroke */ 399 } 400 401 finish(0); /* we are done */ 402} 403 404static void finish(int sig) 405{ 406 endwin(); 407 408 /* do your non-curses wrapup here */ 409 410 exit(0); 411} 412 413 Starting up 414 415 In order to use the screen package, the routines must know about 416 terminal characteristics, and the space for curscr and stdscr must be 417 allocated. These function initscr() does both these things. Since it 418 must allocate space for the windows, it can overflow memory when 419 attempting to do so. On the rare occasions this happens, initscr() 420 will terminate the program with an error message. initscr() must 421 always be called before any of the routines which affect windows are 422 used. If it is not, the program will core dump as soon as either 423 curscr or stdscr are referenced. However, it is usually best to wait 424 to call it until after you are sure you will need it, like after 425 checking for startup errors. Terminal status changing routines like 426 nl() and cbreak() should be called after initscr(). 427 428 Once the screen windows have been allocated, you can set them up for 429 your program. If you want to, say, allow a screen to scroll, use 430 scrollok(). If you want the cursor to be left in place after the last 431 change, use leaveok(). If this is not done, refresh() will move the 432 cursor to the window's current (y, x) coordinates after updating it. 433 434 You can create new windows of your own using the functions newwin(), 435 derwin(), and subwin(). The routine delwin() will allow you to get rid 436 of old windows. All the options described above can be applied to any 437 window. 438 439 Output 440 441 Now that we have set things up, we will want to actually update the 442 terminal. The basic functions used to change what will go on a window 443 are addch() and move(). addch() adds a character at the current (y, x) 444 coordinates. move() changes the current (y, x) coordinates to whatever 445 you want them to be. It returns ERR if you try to move off the window. 446 As mentioned above, you can combine the two into mvaddch() to do both 447 things at once. 448 449 The other output functions, such as addstr() and printw(), all call 450 addch() to add characters to the window. 451 452 After you have put on the window what you want there, when you want 453 the portion of the terminal covered by the window to be made to look 454 like it, you must call refresh(). In order to optimize finding 455 changes, refresh() assumes that any part of the window not changed 456 since the last refresh() of that window has not been changed on the 457 terminal, i.e., that you have not refreshed a portion of the terminal 458 with an overlapping window. If this is not the case, the routine 459 touchwin() is provided to make it look like the entire window has been 460 changed, thus making refresh() check the whole subsection of the 461 terminal for changes. 462 463 If you call wrefresh() with curscr as its argument, it will make the 464 screen look like curscr thinks it looks like. This is useful for 465 implementing a command which would redraw the screen in case it get 466 messed up. 467 468 Input 469 470 The complementary function to addch() is getch() which, if echo is 471 set, will call addch() to echo the character. Since the screen package 472 needs to know what is on the terminal at all times, if characters are 473 to be echoed, the tty must be in raw or cbreak mode. Since initially 474 the terminal has echoing enabled and is in ordinary "cooked" mode, one 475 or the other has to changed before calling getch(); otherwise, the 476 program's output will be unpredictable. 477 478 When you need to accept line-oriented input in a window, the functions 479 wgetstr() and friends are available. There is even a wscanw() function 480 that can do scanf()(3)-style multi-field parsing on window input. 481 These pseudo-line-oriented functions turn on echoing while they 482 execute. 483 484 The example code above uses the call keypad(stdscr, TRUE) to enable 485 support for function-key mapping. With this feature, the getch() code 486 watches the input stream for character sequences that correspond to 487 arrow and function keys. These sequences are returned as 488 pseudo-character values. The #define values returned are listed in the 489 curses.h The mapping from sequences to #define values is determined by 490 key_ capabilities in the terminal's terminfo entry. 491 492 Using Forms Characters 493 494 The addch() function (and some others, including box() and border()) 495 can accept some pseudo-character arguments which are specially defined 496 by ncurses. These are #define values set up in the curses.h header; 497 see there for a complete list (look for the prefix ACS_). 498 499 The most useful of the ACS defines are the forms-drawing characters. 500 You can use these to draw boxes and simple graphs on the screen. If 501 the terminal does not have such characters, curses.h will map them to 502 a recognizable (though ugly) set of ASCII defaults. 503 504 Character Attributes and Color 505 506 The ncurses package supports screen highlights including standout, 507 reverse-video, underline, and blink. It also supports color, which is 508 treated as another kind of highlight. 509 510 Highlights are encoded, internally, as high bits of the 511 pseudo-character type (chtype) that curses.h uses to represent the 512 contents of a screen cell. See the curses.h header file for a complete 513 list of highlight mask values (look for the prefix A_). 514 515 There are two ways to make highlights. One is to logical-or the value 516 of the highlights you want into the character argument of an addch() 517 call, or any other output call that takes a chtype argument. 518 519 The other is to set the current-highlight value. This is logical-ORed 520 with any highlight you specify the first way. You do this with the 521 functions attron(), attroff(), and attrset(); see the manual pages for 522 details. Color is a special kind of highlight. The package actually 523 thinks in terms of color pairs, combinations of foreground and 524 background colors. The sample code above sets up eight color pairs, 525 all of the guaranteed-available colors on black. Note that each color 526 pair is, in effect, given the name of its foreground color. Any other 527 range of eight non-conflicting values could have been used as the 528 first arguments of the init_pair() values. 529 530 Once you have done an init_pair() that creates color-pair N, you can 531 use COLOR_PAIR(N) as a highlight that invokes that particular color 532 combination. Note that COLOR_PAIR(N), for constant N, is itself a 533 compile-time constant and can be used in initializers. 534 535 Mouse Interfacing 536 537 The ncurses library also provides a mouse interface. 538 539 NOTE: this facility is specific to ncurses, it is not part of 540 either the XSI Curses standard, nor of System V Release 4, nor BSD 541 curses. System V Release 4 curses contains code with similar 542 interface definitions, however it is not documented. Other than by 543 disassembling the library, we have no way to determine exactly how 544 that mouse code works. Thus, we recommend that you wrap 545 mouse-related code in an #ifdef using the feature macro 546 NCURSES_MOUSE_VERSION so it will not be compiled and linked on 547 non-ncurses systems. 548 549 Presently, mouse event reporting works in the following environments: 550 * xterm and similar programs such as rxvt. 551 * Linux console, when configured with gpm(1), Alessandro Rubini's 552 mouse server. 553 * FreeBSD sysmouse (console) 554 * OS/2 EMX 555 556 The mouse interface is very simple. To activate it, you use the 557 function mousemask(), passing it as first argument a bit-mask that 558 specifies what kinds of events you want your program to be able to 559 see. It will return the bit-mask of events that actually become 560 visible, which may differ from the argument if the mouse device is not 561 capable of reporting some of the event types you specify. 562 563 Once the mouse is active, your application's command loop should watch 564 for a return value of KEY_MOUSE from wgetch(). When you see this, a 565 mouse event report has been queued. To pick it off the queue, use the 566 function getmouse() (you must do this before the next wgetch(), 567 otherwise another mouse event might come in and make the first one 568 inaccessible). 569 570 Each call to getmouse() fills a structure (the address of which you 571 will pass it) with mouse event data. The event data includes 572 zero-origin, screen-relative character-cell coordinates of the mouse 573 pointer. It also includes an event mask. Bits in this mask will be 574 set, corresponding to the event type being reported. 575 576 The mouse structure contains two additional fields which may be 577 significant in the future as ncurses interfaces to new kinds of 578 pointing device. In addition to x and y coordinates, there is a slot 579 for a z coordinate; this might be useful with touch-screens that can 580 return a pressure or duration parameter. There is also a device ID 581 field, which could be used to distinguish between multiple pointing 582 devices. 583 584 The class of visible events may be changed at any time via 585 mousemask(). Events that can be reported include presses, releases, 586 single-, double- and triple-clicks (you can set the maximum 587 button-down time for clicks). If you do not make clicks visible, they 588 will be reported as press-release pairs. In some environments, the 589 event mask may include bits reporting the state of shift, alt, and 590 ctrl keys on the keyboard during the event. 591 592 A function to check whether a mouse event fell within a given window 593 is also supplied. You can use this to see whether a given window 594 should consider a mouse event relevant to it. 595 596 Because mouse event reporting will not be available in all 597 environments, it would be unwise to build ncurses applications that 598 require the use of a mouse. Rather, you should use the mouse as a 599 shortcut for point-and-shoot commands your application would normally 600 accept from the keyboard. Two of the test games in the ncurses 601 distribution (bs and knight) contain code that illustrates how this 602 can be done. 603 604 See the manual page curs_mouse(3X) for full details of the 605 mouse-interface functions. 606 607 Finishing Up 608 609 In order to clean up after the ncurses routines, the routine endwin() 610 is provided. It restores tty modes to what they were when initscr() 611 was first called, and moves the cursor down to the lower-left corner. 612 Thus, anytime after the call to initscr, endwin() should be called 613 before exiting. 614 615 Function Descriptions 616 617 We describe the detailed behavior of some important curses functions 618 here, as a supplement to the manual page descriptions. 619 620 Initialization and Wrapup 621 622 initscr() 623 The first function called should almost always be initscr(). 624 This will determine the terminal type and initialize curses 625 data structures. initscr() also arranges that the first call to 626 refresh() will clear the screen. If an error occurs a message 627 is written to standard error and the program exits. Otherwise 628 it returns a pointer to stdscr. A few functions may be called 629 before initscr (slk_init(), filter(), ripoffline(), use_env(), 630 and, if you are using multiple terminals, newterm().) 631 632 endwin() 633 Your program should always call endwin() before exiting or 634 shelling out of the program. This function will restore tty 635 modes, move the cursor to the lower left corner of the screen, 636 reset the terminal into the proper non-visual mode. Calling 637 refresh() or doupdate() after a temporary escape from the 638 program will restore the ncurses screen from before the escape. 639 640 newterm(type, ofp, ifp) 641 A program which outputs to more than one terminal should use 642 newterm() instead of initscr(). newterm() should be called once 643 for each terminal. It returns a variable of type SCREEN * which 644 should be saved as a reference to that terminal. (NOTE: a 645 SCREEN variable is not a screen in the sense we are describing 646 in this introduction, but a collection of parameters used to 647 assist in optimizing the display.) The arguments are the type 648 of the terminal (a string) and FILE pointers for the output and 649 input of the terminal. If type is NULL then the environment 650 variable $TERM is used. endwin() should called once at wrapup 651 time for each terminal opened using this function. 652 653 set_term(new) 654 This function is used to switch to a different terminal 655 previously opened by newterm(). The screen reference for the 656 new terminal is passed as the parameter. The previous terminal 657 is returned by the function. All other calls affect only the 658 current terminal. 659 660 delscreen(sp) 661 The inverse of newterm(); deallocates the data structures 662 associated with a given SCREEN reference. 663 664 Causing Output to the Terminal 665 666 refresh() and wrefresh(win) 667 These functions must be called to actually get any output on 668 the terminal, as other routines merely manipulate data 669 structures. wrefresh() copies the named window to the physical 670 terminal screen, taking into account what is already there in 671 order to do optimizations. refresh() does a refresh of stdscr. 672 Unless leaveok() has been enabled, the physical cursor of the 673 terminal is left at the location of the window's cursor. 674 675 doupdate() and wnoutrefresh(win) 676 These two functions allow multiple updates with more efficiency 677 than wrefresh. To use them, it is important to understand how 678 curses works. In addition to all the window structures, curses 679 keeps two data structures representing the terminal screen: a 680 physical screen, describing what is actually on the screen, and 681 a virtual screen, describing what the programmer wants to have 682 on the screen. wrefresh works by first copying the named window 683 to the virtual screen (wnoutrefresh()), and then calling the 684 routine to update the screen (doupdate()). If the programmer 685 wishes to output several windows at once, a series of calls to 686 wrefresh will result in alternating calls to wnoutrefresh() and 687 doupdate(), causing several bursts of output to the screen. By 688 calling wnoutrefresh() for each window, it is then possible to 689 call doupdate() once, resulting in only one burst of output, 690 with fewer total characters transmitted (this also avoids a 691 visually annoying flicker at each update). 692 693 Low-Level Capability Access 694 695 setupterm(term, filenum, errret) 696 This routine is called to initialize a terminal's description, 697 without setting up the curses screen structures or changing the 698 tty-driver mode bits. term is the character string representing 699 the name of the terminal being used. filenum is the UNIX file 700 descriptor of the terminal to be used for output. errret is a 701 pointer to an integer, in which a success or failure indication 702 is returned. The values returned can be 1 (all is well), 0 (no 703 such terminal), or -1 (some problem locating the terminfo 704 database). 705 706 The value of term can be given as NULL, which will cause the 707 value of TERM in the environment to be used. The errret pointer 708 can also be given as NULL, meaning no error code is wanted. If 709 errret is defaulted, and something goes wrong, setupterm() will 710 print an appropriate error message and exit, rather than 711 returning. Thus, a simple program can call setupterm(0, 1, 0) 712 and not worry about initialization errors. 713 714 After the call to setupterm(), the global variable cur_term is 715 set to point to the current structure of terminal capabilities. 716 By calling setupterm() for each terminal, and saving and 717 restoring cur_term, it is possible for a program to use two or 718 more terminals at once. Setupterm() also stores the names 719 section of the terminal description in the global character 720 array ttytype[]. Subsequent calls to setupterm() will overwrite 721 this array, so you will have to save it yourself if need be. 722 723 Debugging 724 725 NOTE: These functions are not part of the standard curses API! 726 727 trace() 728 This function can be used to explicitly set a trace level. If 729 the trace level is nonzero, execution of your program will 730 generate a file called "trace" in the current working directory 731 containing a report on the library's actions. Higher trace 732 levels enable more detailed (and verbose) reporting -- see 733 comments attached to TRACE_ defines in the curses.h file for 734 details. (It is also possible to set a trace level by assigning 735 a trace level value to the environment variable NCURSES_TRACE). 736 737 _tracef() 738 This function can be used to output your own debugging 739 information. It is only available only if you link with 740 -lncurses_g. It can be used the same way as printf(), only it 741 outputs a newline after the end of arguments. The output goes 742 to a file called trace in the current directory. 743 744 Trace logs can be difficult to interpret due to the sheer volume of 745 data dumped in them. There is a script called tracemunch included with 746 the ncurses distribution that can alleviate this problem somewhat; it 747 compacts long sequences of similar operations into more succinct 748 single-line pseudo-operations. These pseudo-ops can be distinguished 749 by the fact that they are named in capital letters. 750 751 Hints, Tips, and Tricks 752 753 The ncurses manual pages are a complete reference for this library. In 754 the remainder of this document, we discuss various useful methods that 755 may not be obvious from the manual page descriptions. 756 757 Some Notes of Caution 758 759 If you find yourself thinking you need to use noraw() or nocbreak(), 760 think again and move carefully. It is probably better design to use 761 getstr() or one of its relatives to simulate cooked mode. The noraw() 762 and nocbreak() functions try to restore cooked mode, but they may end 763 up clobbering some control bits set before you started your 764 application. Also, they have always been poorly documented, and are 765 likely to hurt your application's usability with other curses 766 libraries. 767 768 Bear in mind that refresh() is a synonym for wrefresh(stdscr). Do not 769 try to mix use of stdscr with use of windows declared by newwin(); a 770 refresh() call will blow them off the screen. The right way to handle 771 this is to use subwin(), or not touch stdscr at all and tile your 772 screen with declared windows which you then wnoutrefresh() somewhere 773 in your program event loop, with a single doupdate() call to trigger 774 actual repainting. 775 776 You are much less likely to run into problems if you design your 777 screen layouts to use tiled rather than overlapping windows. 778 Historically, curses support for overlapping windows has been weak, 779 fragile, and poorly documented. The ncurses library is not yet an 780 exception to this rule. 781 782 There is a panels library included in the ncurses distribution that 783 does a pretty good job of strengthening the overlapping-windows 784 facilities. 785 786 Try to avoid using the global variables LINES and COLS. Use getmaxyx() 787 on the stdscr context instead. Reason: your code may be ported to run 788 in an environment with window resizes, in which case several screens 789 could be open with different sizes. 790 791 Temporarily Leaving NCURSES Mode 792 793 Sometimes you will want to write a program that spends most of its 794 time in screen mode, but occasionally returns to ordinary "cooked" 795 mode. A common reason for this is to support shell-out. This behavior 796 is simple to arrange in ncurses. 797 798 To leave ncurses mode, call endwin() as you would if you were 799 intending to terminate the program. This will take the screen back to 800 cooked mode; you can do your shell-out. When you want to return to 801 ncurses mode, simply call refresh() or doupdate(). This will repaint 802 the screen. 803 804 There is a boolean function, isendwin(), which code can use to test 805 whether ncurses screen mode is active. It returns TRUE in the interval 806 between an endwin() call and the following refresh(), FALSE otherwise. 807 808 Here is some sample code for shellout: 809 addstr("Shelling out..."); 810 def_prog_mode(); /* save current tty modes */ 811 endwin(); /* restore original tty modes */ 812 system("sh"); /* run shell */ 813 addstr("returned.\n"); /* prepare return message */ 814 refresh(); /* restore save modes, repaint screen */ 815 816 Using NCURSES under XTERM 817 818 A resize operation in X sends SIGWINCH to the application running 819 under xterm. The easiest way to handle SIGWINCH is to do an endwin, 820 followed by an refresh and a screen repaint you code yourself. The 821 refresh will pick up the new screen size from the xterm's environment. 822 823 That is the standard way, of course (it even works with some vendor's 824 curses implementations). Its drawback is that it clears the screen to 825 reinitialize the display, and does not resize subwindows which must be 826 shrunk. Ncurses provides an extension which works better, the 827 resizeterm function. That function ensures that all windows are 828 limited to the new screen dimensions, and pads stdscr with blanks if 829 the screen is larger. 830 831 The ncurses library provides a SIGWINCH signal handler, which pushes a 832 KEY_RESIZE via the wgetch() calls. When ncurses returns that code, it 833 calls resizeterm to update the size of the standard screen's window, 834 repainting that (filling with blanks or truncating as needed). It also 835 resizes other windows, but its effect may be less satisfactory because 836 it cannot know how you want the screen re-painted. You will usually 837 have to write special-purpose code to handle KEY_RESIZE yourself. 838 839 Handling Multiple Terminal Screens 840 841 The initscr() function actually calls a function named newterm() to do 842 most of its work. If you are writing a program that opens multiple 843 terminals, use newterm() directly. 844 845 For each call, you will have to specify a terminal type and a pair of 846 file pointers; each call will return a screen reference, and stdscr 847 will be set to the last one allocated. You will switch between screens 848 with the set_term call. Note that you will also have to call 849 def_shell_mode and def_prog_mode on each tty yourself. 850 851 Testing for Terminal Capabilities 852 853 Sometimes you may want to write programs that test for the presence of 854 various capabilities before deciding whether to go into ncurses mode. 855 An easy way to do this is to call setupterm(), then use the functions 856 tigetflag(), tigetnum(), and tigetstr() to do your testing. 857 858 A particularly useful case of this often comes up when you want to 859 test whether a given terminal type should be treated as "smart" 860 (cursor-addressable) or "stupid". The right way to test this is to see 861 if the return value of tigetstr("cup") is non-NULL. Alternatively, you 862 can include the term.h file and test the value of the macro 863 cursor_address. 864 865 Tuning for Speed 866 867 Use the addchstr() family of functions for fast screen-painting of 868 text when you know the text does not contain any control characters. 869 Try to make attribute changes infrequent on your screens. Do not use 870 the immedok() option! 871 872 Special Features of NCURSES 873 874 The wresize() function allows you to resize a window in place. The 875 associated resizeterm() function simplifies the construction of 876 SIGWINCH handlers, for resizing all windows. 877 878 The define_key() function allows you to define at runtime function-key 879 control sequences which are not in the terminal description. The 880 keyok() function allows you to temporarily enable or disable 881 interpretation of any function-key control sequence. 882 883 The use_default_colors() function allows you to construct applications 884 which can use the terminal's default foreground and background colors 885 as an additional "default" color. Several terminal emulators support 886 this feature, which is based on ISO 6429. 887 888 Ncurses supports up 16 colors, unlike SVr4 curses which defines only 889 8. While most terminals which provide color allow only 8 colors, about 890 a quarter (including XFree86 xterm) support 16 colors. 891 892 Compatibility with Older Versions 893 894 Despite our best efforts, there are some differences between ncurses 895 and the (undocumented!) behavior of older curses implementations. 896 These arise from ambiguities or omissions in the documentation of the 897 API. 898 899 Refresh of Overlapping Windows 900 901 If you define two windows A and B that overlap, and then alternately 902 scribble on and refresh them, the changes made to the overlapping 903 region under historic curses versions were often not documented 904 precisely. 905 906 To understand why this is a problem, remember that screen updates are 907 calculated between two representations of the entire display. The 908 documentation says that when you refresh a window, it is first copied 909 to the virtual screen, and then changes are calculated to update the 910 physical screen (and applied to the terminal). But "copied to" is not 911 very specific, and subtle differences in how copying works can produce 912 different behaviors in the case where two overlapping windows are each 913 being refreshed at unpredictable intervals. 914 915 What happens to the overlapping region depends on what wnoutrefresh() 916 does with its argument -- what portions of the argument window it 917 copies to the virtual screen. Some implementations do "change copy", 918 copying down only locations in the window that have changed (or been 919 marked changed with wtouchln() and friends). Some implementations do 920 "entire copy", copying all window locations to the virtual screen 921 whether or not they have changed. 922 923 The ncurses library itself has not always been consistent on this 924 score. Due to a bug, versions 1.8.7 to 1.9.8a did entire copy. 925 Versions 1.8.6 and older, and versions 1.9.9 and newer, do change 926 copy. 927 928 For most commercial curses implementations, it is not documented and 929 not known for sure (at least not to the ncurses maintainers) whether 930 they do change copy or entire copy. We know that System V release 3 931 curses has logic in it that looks like an attempt to do change copy, 932 but the surrounding logic and data representations are sufficiently 933 complex, and our knowledge sufficiently indirect, that it is hard to 934 know whether this is reliable. It is not clear what the SVr4 935 documentation and XSI standard intend. The XSI Curses standard barely 936 mentions wnoutrefresh(); the SVr4 documents seem to be describing 937 entire-copy, but it is possible with some effort and straining to read 938 them the other way. 939 940 It might therefore be unwise to rely on either behavior in programs 941 that might have to be linked with other curses implementations. 942 Instead, you can do an explicit touchwin() before the wnoutrefresh() 943 call to guarantee an entire-contents copy anywhere. 944 945 The really clean way to handle this is to use the panels library. If, 946 when you want a screen update, you do update_panels(), it will do all 947 the necessary wnoutrefresh() calls for whatever panel stacking order 948 you have defined. Then you can do one doupdate() and there will be a 949 single burst of physical I/O that will do all your updates. 950 951 Background Erase 952 953 If you have been using a very old versions of ncurses (1.8.7 or older) 954 you may be surprised by the behavior of the erase functions. In older 955 versions, erased areas of a window were filled with a blank modified 956 by the window's current attribute (as set by wattrset(), wattron(), 957 wattroff() and friends). 958 959 In newer versions, this is not so. Instead, the attribute of erased 960 blanks is normal unless and until it is modified by the functions 961 bkgdset() or wbkgdset(). 962 963 This change in behavior conforms ncurses to System V Release 4 and the 964 XSI Curses standard. 965 966 XSI Curses Conformance 967 968 The ncurses library is intended to be base-level conformant with the 969 XSI Curses standard from X/Open. Many extended-level features (in 970 fact, almost all features not directly concerned with wide characters 971 and internationalization) are also supported. 972 973 One effect of XSI conformance is the change in behavior described 974 under "Background Erase -- Compatibility with Old Versions". 975 976 Also, ncurses meets the XSI requirement that every macro entry point 977 have a corresponding function which may be linked (and will be 978 prototype-checked) if the macro definition is disabled with #undef. 979 980The Panels Library 981 982 The ncurses library by itself provides good support for screen 983 displays in which the windows are tiled (non-overlapping). In the more 984 general case that windows may overlap, you have to use a series of 985 wnoutrefresh() calls followed by a doupdate(), and be careful about 986 the order you do the window refreshes in. It has to be bottom-upwards, 987 otherwise parts of windows that should be obscured will show through. 988 989 When your interface design is such that windows may dive deeper into 990 the visibility stack or pop to the top at runtime, the resulting 991 book-keeping can be tedious and difficult to get right. Hence the 992 panels library. 993 994 The panel library first appeared in AT&T System V. The version 995 documented here is the panel code distributed with ncurses. 996 997 Compiling With the Panels Library 998 999 Your panels-using modules must import the panels library declarations 1000 with 1001 #include <panel.h> 1002 1003 and must be linked explicitly with the panels library using an -lpanel 1004 argument. Note that they must also link the ncurses library with 1005 -lncurses. Many linkers are two-pass and will accept either order, but 1006 it is still good practice to put -lpanel first and -lncurses second. 1007 1008 Overview of Panels 1009 1010 A panel object is a window that is implicitly treated as part of a 1011 deck including all other panel objects. The deck has an implicit 1012 bottom-to-top visibility order. The panels library includes an update 1013 function (analogous to refresh()) that displays all panels in the deck 1014 in the proper order to resolve overlaps. The standard window, stdscr, 1015 is considered below all panels. 1016 1017 Details on the panels functions are available in the man pages. We 1018 will just hit the highlights here. 1019 1020 You create a panel from a window by calling new_panel() on a window 1021 pointer. It then becomes the top of the deck. The panel's window is 1022 available as the value of panel_window() called with the panel pointer 1023 as argument. 1024 1025 You can delete a panel (removing it from the deck) with del_panel. 1026 This will not deallocate the associated window; you have to do that 1027 yourself. You can replace a panel's window with a different window by 1028 calling replace_window. The new window may be of different size; the 1029 panel code will re-compute all overlaps. This operation does not 1030 change the panel's position in the deck. 1031 1032 To move a panel's window, use move_panel(). The mvwin() function on 1033 the panel's window is not sufficient because it does not update the 1034 panels library's representation of where the windows are. This 1035 operation leaves the panel's depth, contents, and size unchanged. 1036 1037 Two functions (top_panel(), bottom_panel()) are provided for 1038 rearranging the deck. The first pops its argument window to the top of 1039 the deck; the second sends it to the bottom. Either operation leaves 1040 the panel's screen location, contents, and size unchanged. 1041 1042 The function update_panels() does all the wnoutrefresh() calls needed 1043 to prepare for doupdate() (which you must call yourself, afterwards). 1044 1045 Typically, you will want to call update_panels() and doupdate() just 1046 before accepting command input, once in each cycle of interaction with 1047 the user. If you call update_panels() after each and every panel 1048 write, you will generate a lot of unnecessary refresh activity and 1049 screen flicker. 1050 1051 Panels, Input, and the Standard Screen 1052 1053 You should not mix wnoutrefresh() or wrefresh() operations with panels 1054 code; this will work only if the argument window is either in the top 1055 panel or unobscured by any other panels. 1056 1057 The stsdcr window is a special case. It is considered below all 1058 panels. Because changes to panels may obscure parts of stdscr, though, 1059 you should call update_panels() before doupdate() even when you only 1060 change stdscr. 1061 1062 Note that wgetch automatically calls wrefresh. Therefore, before 1063 requesting input from a panel window, you need to be sure that the 1064 panel is totally unobscured. 1065 1066 There is presently no way to display changes to one obscured panel 1067 without repainting all panels. 1068 1069 Hiding Panels 1070 1071 It is possible to remove a panel from the deck temporarily; use 1072 hide_panel for this. Use show_panel() to render it visible again. The 1073 predicate function panel_hidden tests whether or not a panel is 1074 hidden. 1075 1076 The panel_update code ignores hidden panels. You cannot do top_panel() 1077 or bottom_panel on a hidden panel(). Other panels operations are 1078 applicable. 1079 1080 Miscellaneous Other Facilities 1081 1082 It is possible to navigate the deck using the functions panel_above() 1083 and panel_below. Handed a panel pointer, they return the panel above 1084 or below that panel. Handed NULL, they return the bottom-most or 1085 top-most panel. 1086 1087 Every panel has an associated user pointer, not used by the panel 1088 code, to which you can attach application data. See the man page 1089 documentation of set_panel_userptr() and panel_userptr for details. 1090 1091The Menu Library 1092 1093 A menu is a screen display that assists the user to choose some subset 1094 of a given set of items. The menu library is a curses extension that 1095 supports easy programming of menu hierarchies with a uniform but 1096 flexible interface. 1097 1098 The menu library first appeared in AT&T System V. The version 1099 documented here is the menu code distributed with ncurses. 1100 1101 Compiling With the menu Library 1102 1103 Your menu-using modules must import the menu library declarations with 1104 #include <menu.h> 1105 1106 and must be linked explicitly with the menus library using an -lmenu 1107 argument. Note that they must also link the ncurses library with 1108 -lncurses. Many linkers are two-pass and will accept either order, but 1109 it is still good practice to put -lmenu first and -lncurses second. 1110 1111 Overview of Menus 1112 1113 The menus created by this library consist of collections of items 1114 including a name string part and a description string part. To make 1115 menus, you create groups of these items and connect them with menu 1116 frame objects. 1117 1118 The menu can then by posted, that is written to an associated window. 1119 Actually, each menu has two associated windows; a containing window in 1120 which the programmer can scribble titles or borders, and a subwindow 1121 in which the menu items proper are displayed. If this subwindow is too 1122 small to display all the items, it will be a scrollable viewport on 1123 the collection of items. 1124 1125 A menu may also be unposted (that is, undisplayed), and finally freed 1126 to make the storage associated with it and its items available for 1127 re-use. 1128 1129 The general flow of control of a menu program looks like this: 1130 1. Initialize curses. 1131 2. Create the menu items, using new_item(). 1132 3. Create the menu using new_menu(). 1133 4. Post the menu using post_menu(). 1134 5. Refresh the screen. 1135 6. Process user requests via an input loop. 1136 7. Unpost the menu using unpost_menu(). 1137 8. Free the menu, using free_menu(). 1138 9. Free the items using free_item(). 1139 10. Terminate curses. 1140 1141 Selecting items 1142 1143 Menus may be multi-valued or (the default) single-valued (see the 1144 manual page menu_opts(3x) to see how to change the default). Both 1145 types always have a current item. 1146 1147 From a single-valued menu you can read the selected value simply by 1148 looking at the current item. From a multi-valued menu, you get the 1149 selected set by looping through the items applying the item_value() 1150 predicate function. Your menu-processing code can use the function 1151 set_item_value() to flag the items in the select set. 1152 1153 Menu items can be made unselectable using set_item_opts() or 1154 item_opts_off() with the O_SELECTABLE argument. This is the only 1155 option so far defined for menus, but it is good practice to code as 1156 though other option bits might be on. 1157 1158 Menu Display 1159 1160 The menu library calculates a minimum display size for your window, 1161 based on the following variables: 1162 * The number and maximum length of the menu items 1163 * Whether the O_ROWMAJOR option is enabled 1164 * Whether display of descriptions is enabled 1165 * Whatever menu format may have been set by the programmer 1166 * The length of the menu mark string used for highlighting selected 1167 items 1168 1169 The function set_menu_format() allows you to set the maximum size of 1170 the viewport or menu page that will be used to display menu items. You 1171 can retrieve any format associated with a menu with menu_format(). The 1172 default format is rows=16, columns=1. 1173 1174 The actual menu page may be smaller than the format size. This depends 1175 on the item number and size and whether O_ROWMAJOR is on. This option 1176 (on by default) causes menu items to be displayed in a "raster-scan" 1177 pattern, so that if more than one item will fit horizontally the first 1178 couple of items are side-by-side in the top row. The alternative is 1179 column-major display, which tries to put the first several items in 1180 the first column. 1181 1182 As mentioned above, a menu format not large enough to allow all items 1183 to fit on-screen will result in a menu display that is vertically 1184 scrollable. 1185 1186 You can scroll it with requests to the menu driver, which will be 1187 described in the section on menu input handling. 1188 1189 Each menu has a mark string used to visually tag selected items; see 1190 the menu_mark(3x) manual page for details. The mark string length also 1191 influences the menu page size. 1192 1193 The function scale_menu() returns the minimum display size that the 1194 menu code computes from all these factors. There are other menu 1195 display attributes including a select attribute, an attribute for 1196 selectable items, an attribute for unselectable items, and a pad 1197 character used to separate item name text from description text. These 1198 have reasonable defaults which the library allows you to change (see 1199 the menu_attribs(3x) manual page. 1200 1201 Menu Windows 1202 1203 Each menu has, as mentioned previously, a pair of associated windows. 1204 Both these windows are painted when the menu is posted and erased when 1205 the menu is unposted. 1206 1207 The outer or frame window is not otherwise touched by the menu 1208 routines. It exists so the programmer can associate a title, a border, 1209 or perhaps help text with the menu and have it properly refreshed or 1210 erased at post/unpost time. The inner window or subwindow is where the 1211 current menu page is displayed. 1212 1213 By default, both windows are stdscr. You can set them with the 1214 functions in menu_win(3x). 1215 1216 When you call post_menu(), you write the menu to its subwindow. When 1217 you call unpost_menu(), you erase the subwindow, However, neither of 1218 these actually modifies the screen. To do that, call wrefresh() or 1219 some equivalent. 1220 1221 Processing Menu Input 1222 1223 The main loop of your menu-processing code should call menu_driver() 1224 repeatedly. The first argument of this routine is a menu pointer; the 1225 second is a menu command code. You should write an input-fetching 1226 routine that maps input characters to menu command codes, and pass its 1227 output to menu_driver(). The menu command codes are fully documented 1228 in menu_driver(3x). 1229 1230 The simplest group of command codes is REQ_NEXT_ITEM, REQ_PREV_ITEM, 1231 REQ_FIRST_ITEM, REQ_LAST_ITEM, REQ_UP_ITEM, REQ_DOWN_ITEM, 1232 REQ_LEFT_ITEM, REQ_RIGHT_ITEM. These change the currently selected 1233 item. These requests may cause scrolling of the menu page if it only 1234 partially displayed. 1235 1236 There are explicit requests for scrolling which also change the 1237 current item (because the select location does not change, but the 1238 item there does). These are REQ_SCR_DLINE, REQ_SCR_ULINE, 1239 REQ_SCR_DPAGE, and REQ_SCR_UPAGE. 1240 1241 The REQ_TOGGLE_ITEM selects or deselects the current item. It is for 1242 use in multi-valued menus; if you use it with O_ONEVALUE on, you will 1243 get an error return (E_REQUEST_DENIED). 1244 1245 Each menu has an associated pattern buffer. The menu_driver() logic 1246 tries to accumulate printable ASCII characters passed in in that 1247 buffer; when it matches a prefix of an item name, that item (or the 1248 next matching item) is selected. If appending a character yields no 1249 new match, that character is deleted from the pattern buffer, and 1250 menu_driver() returns E_NO_MATCH. 1251 1252 Some requests change the pattern buffer directly: REQ_CLEAR_PATTERN, 1253 REQ_BACK_PATTERN, REQ_NEXT_MATCH, REQ_PREV_MATCH. The latter two are 1254 useful when pattern buffer input matches more than one item in a 1255 multi-valued menu. 1256 1257 Each successful scroll or item navigation request clears the pattern 1258 buffer. It is also possible to set the pattern buffer explicitly with 1259 set_menu_pattern(). 1260 1261 Finally, menu driver requests above the constant MAX_COMMAND are 1262 considered application-specific commands. The menu_driver() code 1263 ignores them and returns E_UNKNOWN_COMMAND. 1264 1265 Miscellaneous Other Features 1266 1267 Various menu options can affect the processing and visual appearance 1268 and input processing of menus. See menu_opts(3x) for details. 1269 1270 It is possible to change the current item from application code; this 1271 is useful if you want to write your own navigation requests. It is 1272 also possible to explicitly set the top row of the menu display. See 1273 mitem_current(3x). If your application needs to change the menu 1274 subwindow cursor for any reason, pos_menu_cursor() will restore it to 1275 the correct location for continuing menu driver processing. 1276 1277 It is possible to set hooks to be called at menu initialization and 1278 wrapup time, and whenever the selected item changes. See 1279 menu_hook(3x). 1280 1281 Each item, and each menu, has an associated user pointer on which you 1282 can hang application data. See mitem_userptr(3x) and menu_userptr(3x). 1283 1284The Forms Library 1285 1286 The form library is a curses extension that supports easy programming 1287 of on-screen forms for data entry and program control. 1288 1289 The form library first appeared in AT&T System V. The version 1290 documented here is the form code distributed with ncurses. 1291 1292 Compiling With the form Library 1293 1294 Your form-using modules must import the form library declarations with 1295 #include <form.h> 1296 1297 and must be linked explicitly with the forms library using an -lform 1298 argument. Note that they must also link the ncurses library with 1299 -lncurses. Many linkers are two-pass and will accept either order, but 1300 it is still good practice to put -lform first and -lncurses second. 1301 1302 Overview of Forms 1303 1304 A form is a collection of fields; each field may be either a label 1305 (explanatory text) or a data-entry location. Long forms may be 1306 segmented into pages; each entry to a new page clears the screen. 1307 1308 To make forms, you create groups of fields and connect them with form 1309 frame objects; the form library makes this relatively simple. 1310 1311 Once defined, a form can be posted, that is written to an associated 1312 window. Actually, each form has two associated windows; a containing 1313 window in which the programmer can scribble titles or borders, and a 1314 subwindow in which the form fields proper are displayed. 1315 1316 As the form user fills out the posted form, navigation and editing 1317 keys support movement between fields, editing keys support modifying 1318 field, and plain text adds to or changes data in a current field. The 1319 form library allows you (the forms designer) to bind each navigation 1320 and editing key to any keystroke accepted by curses Fields may have 1321 validation conditions on them, so that they check input data for type 1322 and value. The form library supplies a rich set of pre-defined field 1323 types, and makes it relatively easy to define new ones. 1324 1325 Once its transaction is completed (or aborted), a form may be unposted 1326 (that is, undisplayed), and finally freed to make the storage 1327 associated with it and its items available for re-use. 1328 1329 The general flow of control of a form program looks like this: 1330 1. Initialize curses. 1331 2. Create the form fields, using new_field(). 1332 3. Create the form using new_form(). 1333 4. Post the form using post_form(). 1334 5. Refresh the screen. 1335 6. Process user requests via an input loop. 1336 7. Unpost the form using unpost_form(). 1337 8. Free the form, using free_form(). 1338 9. Free the fields using free_field(). 1339 10. Terminate curses. 1340 1341 Note that this looks much like a menu program; the form library 1342 handles tasks which are in many ways similar, and its interface was 1343 obviously designed to resemble that of the menu library wherever 1344 possible. 1345 1346 In forms programs, however, the "process user requests" is somewhat 1347 more complicated than for menus. Besides menu-like navigation 1348 operations, the menu driver loop has to support field editing and data 1349 validation. 1350 1351 Creating and Freeing Fields and Forms 1352 1353 The basic function for creating fields is new_field(): 1354FIELD *new_field(int height, int width, /* new field size */ 1355 int top, int left, /* upper left corner */ 1356 int offscreen, /* number of offscreen rows */ 1357 int nbuf); /* number of working buffers */ 1358 1359 Menu items always occupy a single row, but forms fields may have 1360 multiple rows. So new_field() requires you to specify a width and 1361 height (the first two arguments, which mist both be greater than 1362 zero). 1363 1364 You must also specify the location of the field's upper left corner on 1365 the screen (the third and fourth arguments, which must be zero or 1366 greater). Note that these coordinates are relative to the form 1367 subwindow, which will coincide with stdscr by default but need not be 1368 stdscr if you have done an explicit set_form_win() call. 1369 1370 The fifth argument allows you to specify a number of off-screen rows. 1371 If this is zero, the entire field will always be displayed. If it is 1372 nonzero, the form will be scrollable, with only one screen-full 1373 (initially the top part) displayed at any given time. If you make a 1374 field dynamic and grow it so it will no longer fit on the screen, the 1375 form will become scrollable even if the offscreen argument was 1376 initially zero. 1377 1378 The forms library allocates one working buffer per field; the size of 1379 each buffer is ((height + offscreen)*width + 1, one character for each 1380 position in the field plus a NUL terminator. The sixth argument is the 1381 number of additional data buffers to allocate for the field; your 1382 application can use them for its own purposes. 1383FIELD *dup_field(FIELD *field, /* field to copy */ 1384 int top, int left); /* location of new copy */ 1385 1386 The function dup_field() duplicates an existing field at a new 1387 location. Size and buffering information are copied; some attribute 1388 flags and status bits are not (see the form_field_new(3X) for 1389 details). 1390FIELD *link_field(FIELD *field, /* field to copy */ 1391 int top, int left); /* location of new copy */ 1392 1393 The function link_field() also duplicates an existing field at a new 1394 location. The difference from dup_field() is that it arranges for the 1395 new field's buffer to be shared with the old one. 1396 1397 Besides the obvious use in making a field editable from two different 1398 form pages, linked fields give you a way to hack in dynamic labels. If 1399 you declare several fields linked to an original, and then make them 1400 inactive, changes from the original will still be propagated to the 1401 linked fields. 1402 1403 As with duplicated fields, linked fields have attribute bits separate 1404 from the original. 1405 1406 As you might guess, all these field-allocations return NULL if the 1407 field allocation is not possible due to an out-of-memory error or 1408 out-of-bounds arguments. 1409 1410 To connect fields to a form, use 1411FORM *new_form(FIELD **fields); 1412 1413 This function expects to see a NULL-terminated array of field 1414 pointers. Said fields are connected to a newly-allocated form object; 1415 its address is returned (or else NULL if the allocation fails). 1416 1417 Note that new_field() does not copy the pointer array into private 1418 storage; if you modify the contents of the pointer array during forms 1419 processing, all manner of bizarre things might happen. Also note that 1420 any given field may only be connected to one form. 1421 1422 The functions free_field() and free_form are available to free field 1423 and form objects. It is an error to attempt to free a field connected 1424 to a form, but not vice-versa; thus, you will generally free your form 1425 objects first. 1426 1427 Fetching and Changing Field Attributes 1428 1429 Each form field has a number of location and size attributes 1430 associated with it. There are other field attributes used to control 1431 display and editing of the field. Some (for example, the O_STATIC bit) 1432 involve sufficient complications to be covered in sections of their 1433 own later on. We cover the functions used to get and set several basic 1434 attributes here. 1435 1436 When a field is created, the attributes not specified by the new_field 1437 function are copied from an invisible system default field. In 1438 attribute-setting and -fetching functions, the argument NULL is taken 1439 to mean this field. Changes to it persist as defaults until your forms 1440 application terminates. 1441 1442 Fetching Size and Location Data 1443 1444 You can retrieve field sizes and locations through: 1445int field_info(FIELD *field, /* field from which to fetch */ 1446 int *height, *int width, /* field size */ 1447 int *top, int *left, /* upper left corner */ 1448 int *offscreen, /* number of offscreen rows */ 1449 int *nbuf); /* number of working buffers */ 1450 1451 This function is a sort of inverse of new_field(); instead of setting 1452 size and location attributes of a new field, it fetches them from an 1453 existing one. 1454 1455 Changing the Field Location 1456 1457 It is possible to move a field's location on the screen: 1458int move_field(FIELD *field, /* field to alter */ 1459 int top, int left); /* new upper-left corner */ 1460 1461 You can, of course. query the current location through field_info(). 1462 1463 The Justification Attribute 1464 1465 One-line fields may be unjustified, justified right, justified left, 1466 or centered. Here is how you manipulate this attribute: 1467int set_field_just(FIELD *field, /* field to alter */ 1468 int justmode); /* mode to set */ 1469 1470int field_just(FIELD *field); /* fetch mode of field */ 1471 1472 The mode values accepted and returned by this functions are 1473 preprocessor macros NO_JUSTIFICATION, JUSTIFY_RIGHT, JUSTIFY_LEFT, or 1474 JUSTIFY_CENTER. 1475 1476 Field Display Attributes 1477 1478 For each field, you can set a foreground attribute for entered 1479 characters, a background attribute for the entire field, and a pad 1480 character for the unfilled portion of the field. You can also control 1481 pagination of the form. 1482 1483 This group of four field attributes controls the visual appearance of 1484 the field on the screen, without affecting in any way the data in the 1485 field buffer. 1486int set_field_fore(FIELD *field, /* field to alter */ 1487 chtype attr); /* attribute to set */ 1488 1489chtype field_fore(FIELD *field); /* field to query */ 1490 1491int set_field_back(FIELD *field, /* field to alter */ 1492 chtype attr); /* attribute to set */ 1493 1494chtype field_back(FIELD *field); /* field to query */ 1495 1496int set_field_pad(FIELD *field, /* field to alter */ 1497 int pad); /* pad character to set */ 1498 1499chtype field_pad(FIELD *field); 1500 1501int set_new_page(FIELD *field, /* field to alter */ 1502 int flag); /* TRUE to force new page */ 1503 1504chtype new_page(FIELD *field); /* field to query */ 1505 1506 The attributes set and returned by the first four functions are normal 1507 curses(3x) display attribute values (A_STANDOUT, A_BOLD, A_REVERSE 1508 etc). The page bit of a field controls whether it is displayed at the 1509 start of a new form screen. 1510 1511 Field Option Bits 1512 1513 There is also a large collection of field option bits you can set to 1514 control various aspects of forms processing. You can manipulate them 1515 with these functions: 1516int set_field_opts(FIELD *field, /* field to alter */ 1517 int attr); /* attribute to set */ 1518 1519int field_opts_on(FIELD *field, /* field to alter */ 1520 int attr); /* attributes to turn on */ 1521 1522int field_opts_off(FIELD *field, /* field to alter */ 1523 int attr); /* attributes to turn off */ 1524 1525int field_opts(FIELD *field); /* field to query */ 1526 1527 By default, all options are on. Here are the available option bits: 1528 1529 O_VISIBLE 1530 Controls whether the field is visible on the screen. Can be 1531 used during form processing to hide or pop up fields depending 1532 on the value of parent fields. 1533 1534 O_ACTIVE 1535 Controls whether the field is active during forms processing 1536 (i.e. visited by form navigation keys). Can be used to make 1537 labels or derived fields with buffer values alterable by the 1538 forms application, not the user. 1539 1540 O_PUBLIC 1541 Controls whether data is displayed during field entry. If this 1542 option is turned off on a field, the library will accept and 1543 edit data in that field, but it will not be displayed and the 1544 visible field cursor will not move. You can turn off the 1545 O_PUBLIC bit to define password fields. 1546 1547 O_EDIT 1548 Controls whether the field's data can be modified. When this 1549 option is off, all editing requests except REQ_PREV_CHOICE and 1550 REQ_NEXT_CHOICE will fail. Such read-only fields may be useful 1551 for help messages. 1552 1553 O_WRAP 1554 Controls word-wrapping in multi-line fields. Normally, when any 1555 character of a (blank-separated) word reaches the end of the 1556 current line, the entire word is wrapped to the next line 1557 (assuming there is one). When this option is off, the word will 1558 be split across the line break. 1559 1560 O_BLANK 1561 Controls field blanking. When this option is on, entering a 1562 character at the first field position erases the entire field 1563 (except for the just-entered character). 1564 1565 O_AUTOSKIP 1566 Controls automatic skip to next field when this one fills. 1567 Normally, when the forms user tries to type more data into a 1568 field than will fit, the editing location jumps to next field. 1569 When this option is off, the user's cursor will hang at the end 1570 of the field. This option is ignored in dynamic fields that 1571 have not reached their size limit. 1572 1573 O_NULLOK 1574 Controls whether validation is applied to blank fields. 1575 Normally, it is not; the user can leave a field blank without 1576 invoking the usual validation check on exit. If this option is 1577 off on a field, exit from it will invoke a validation check. 1578 1579 O_PASSOK 1580 Controls whether validation occurs on every exit, or only after 1581 the field is modified. Normally the latter is true. Setting 1582 O_PASSOK may be useful if your field's validation function may 1583 change during forms processing. 1584 1585 O_STATIC 1586 Controls whether the field is fixed to its initial dimensions. 1587 If you turn this off, the field becomes dynamic and will 1588 stretch to fit entered data. 1589 1590 A field's options cannot be changed while the field is currently 1591 selected. However, options may be changed on posted fields that are 1592 not current. 1593 1594 The option values are bit-masks and can be composed with logical-or in 1595 the obvious way. 1596 1597 Field Status 1598 1599 Every field has a status flag, which is set to FALSE when the field is 1600 created and TRUE when the value in field buffer 0 changes. This flag 1601 can be queried and set directly: 1602int set_field_status(FIELD *field, /* field to alter */ 1603 int status); /* mode to set */ 1604 1605int field_status(FIELD *field); /* fetch mode of field */ 1606 1607 Setting this flag under program control can be useful if you use the 1608 same form repeatedly, looking for modified fields each time. 1609 1610 Calling field_status() on a field not currently selected for input 1611 will return a correct value. Calling field_status() on a field that is 1612 currently selected for input may not necessarily give a correct field 1613 status value, because entered data is not necessarily copied to buffer 1614 zero before the exit validation check. To guarantee that the returned 1615 status value reflects reality, call field_status() either (1) in the 1616 field's exit validation check routine, (2) from the field's or form's 1617 initialization or termination hooks, or (3) just after a 1618 REQ_VALIDATION request has been processed by the forms driver. 1619 1620 Field User Pointer 1621 1622 Each field structure contains one character pointer slot that is not 1623 used by the forms library. It is intended to be used by applications 1624 to store private per-field data. You can manipulate it with: 1625int set_field_userptr(FIELD *field, /* field to alter */ 1626 char *userptr); /* mode to set */ 1627 1628char *field_userptr(FIELD *field); /* fetch mode of field */ 1629 1630 (Properly, this user pointer field ought to have (void *) type. The 1631 (char *) type is retained for System V compatibility.) 1632 1633 It is valid to set the user pointer of the default field (with a 1634 set_field_userptr() call passed a NULL field pointer.) When a new 1635 field is created, the default-field user pointer is copied to 1636 initialize the new field's user pointer. 1637 1638 Variable-Sized Fields 1639 1640 Normally, a field is fixed at the size specified for it at creation 1641 time. If, however, you turn off its O_STATIC bit, it becomes dynamic 1642 and will automatically resize itself to accommodate data as it is 1643 entered. If the field has extra buffers associated with it, they will 1644 grow right along with the main input buffer. 1645 1646 A one-line dynamic field will have a fixed height (1) but variable 1647 width, scrolling horizontally to display data within the field area as 1648 originally dimensioned and located. A multi-line dynamic field will 1649 have a fixed width, but variable height (number of rows), scrolling 1650 vertically to display data within the field area as originally 1651 dimensioned and located. 1652 1653 Normally, a dynamic field is allowed to grow without limit. But it is 1654 possible to set an upper limit on the size of a dynamic field. You do 1655 it with this function: 1656int set_max_field(FIELD *field, /* field to alter (may not be NULL) */ 1657 int max_size); /* upper limit on field size */ 1658 1659 If the field is one-line, max_size is taken to be a column size limit; 1660 if it is multi-line, it is taken to be a line size limit. To disable 1661 any limit, use an argument of zero. The growth limit can be changed 1662 whether or not the O_STATIC bit is on, but has no effect until it is. 1663 1664 The following properties of a field change when it becomes dynamic: 1665 * If there is no growth limit, there is no final position of the 1666 field; therefore O_AUTOSKIP and O_NL_OVERLOAD are ignored. 1667 * Field justification will be ignored (though whatever justification 1668 is set up will be retained internally and can be queried). 1669 * The dup_field() and link_field() calls copy dynamic-buffer sizes. 1670 If the O_STATIC option is set on one of a collection of links, 1671 buffer resizing will occur only when the field is edited through 1672 that link. 1673 * The call field_info() will retrieve the original static size of 1674 the field; use dynamic_field_info() to get the actual dynamic 1675 size. 1676 1677 Field Validation 1678 1679 By default, a field will accept any data that will fit in its input 1680 buffer. However, it is possible to attach a validation type to a 1681 field. If you do this, any attempt to leave the field while it 1682 contains data that does not match the validation type will fail. Some 1683 validation types also have a character-validity check for each time a 1684 character is entered in the field. 1685 1686 A field's validation check (if any) is not called when 1687 set_field_buffer() modifies the input buffer, nor when that buffer is 1688 changed through a linked field. 1689 1690 The form library provides a rich set of pre-defined validation types, 1691 and gives you the capability to define custom ones of your own. You 1692 can examine and change field validation attributes with the following 1693 functions: 1694int set_field_type(FIELD *field, /* field to alter */ 1695 FIELDTYPE *ftype, /* type to associate */ 1696 ...); /* additional arguments*/ 1697 1698FIELDTYPE *field_type(FIELD *field); /* field to query */ 1699 1700 The validation type of a field is considered an attribute of the 1701 field. As with other field attributes, Also, doing set_field_type() 1702 with a NULL field default will change the system default for 1703 validation of newly-created fields. 1704 1705 Here are the pre-defined validation types: 1706 1707 TYPE_ALPHA 1708 1709 This field type accepts alphabetic data; no blanks, no digits, no 1710 special characters (this is checked at character-entry time). It is 1711 set up with: 1712int set_field_type(FIELD *field, /* field to alter */ 1713 TYPE_ALPHA, /* type to associate */ 1714 int width); /* maximum width of field */ 1715 1716 The width argument sets a minimum width of data. Typically you will 1717 want to set this to the field width; if it is greater than the field 1718 width, the validation check will always fail. A minimum width of zero 1719 makes field completion optional. 1720 1721 TYPE_ALNUM 1722 1723 This field type accepts alphabetic data and digits; no blanks, no 1724 special characters (this is checked at character-entry time). It is 1725 set up with: 1726int set_field_type(FIELD *field, /* field to alter */ 1727 TYPE_ALNUM, /* type to associate */ 1728 int width); /* maximum width of field */ 1729 1730 The width argument sets a minimum width of data. As with TYPE_ALPHA, 1731 typically you will want to set this to the field width; if it is 1732 greater than the field width, the validation check will always fail. A 1733 minimum width of zero makes field completion optional. 1734 1735 TYPE_ENUM 1736 1737 This type allows you to restrict a field's values to be among a 1738 specified set of string values (for example, the two-letter postal 1739 codes for U.S. states). It is set up with: 1740int set_field_type(FIELD *field, /* field to alter */ 1741 TYPE_ENUM, /* type to associate */ 1742 char **valuelist; /* list of possible values */ 1743 int checkcase; /* case-sensitive? */ 1744 int checkunique); /* must specify uniquely? */ 1745 1746 The valuelist parameter must point at a NULL-terminated list of valid 1747 strings. The checkcase argument, if true, makes comparison with the 1748 string case-sensitive. 1749 1750 When the user exits a TYPE_ENUM field, the validation procedure tries 1751 to complete the data in the buffer to a valid entry. If a complete 1752 choice string has been entered, it is of course valid. But it is also 1753 possible to enter a prefix of a valid string and have it completed for 1754 you. 1755 1756 By default, if you enter such a prefix and it matches more than one 1757 value in the string list, the prefix will be completed to the first 1758 matching value. But the checkunique argument, if true, requires prefix 1759 matches to be unique in order to be valid. 1760 1761 The REQ_NEXT_CHOICE and REQ_PREV_CHOICE input requests can be 1762 particularly useful with these fields. 1763 1764 TYPE_INTEGER 1765 1766 This field type accepts an integer. It is set up as follows: 1767int set_field_type(FIELD *field, /* field to alter */ 1768 TYPE_INTEGER, /* type to associate */ 1769 int padding, /* # places to zero-pad to */ 1770 int vmin, int vmax); /* valid range */ 1771 1772 Valid characters consist of an optional leading minus and digits. The 1773 range check is performed on exit. If the range maximum is less than or 1774 equal to the minimum, the range is ignored. 1775 1776 If the value passes its range check, it is padded with as many leading 1777 zero digits as necessary to meet the padding argument. 1778 1779 A TYPE_INTEGER value buffer can conveniently be interpreted with the C 1780 library function atoi(3). 1781 1782 TYPE_NUMERIC 1783 1784 This field type accepts a decimal number. It is set up as follows: 1785int set_field_type(FIELD *field, /* field to alter */ 1786 TYPE_NUMERIC, /* type to associate */ 1787 int padding, /* # places of precision */ 1788 double vmin, double vmax); /* valid range */ 1789 1790 Valid characters consist of an optional leading minus and digits. 1791 possibly including a decimal point. If your system supports locale's, 1792 the decimal point character used must be the one defined by your 1793 locale. The range check is performed on exit. If the range maximum is 1794 less than or equal to the minimum, the range is ignored. 1795 1796 If the value passes its range check, it is padded with as many 1797 trailing zero digits as necessary to meet the padding argument. 1798 1799 A TYPE_NUMERIC value buffer can conveniently be interpreted with the C 1800 library function atof(3). 1801 1802 TYPE_REGEXP 1803 1804 This field type accepts data matching a regular expression. It is set 1805 up as follows: 1806int set_field_type(FIELD *field, /* field to alter */ 1807 TYPE_REGEXP, /* type to associate */ 1808 char *regexp); /* expression to match */ 1809 1810 The syntax for regular expressions is that of regcomp(3). The check 1811 for regular-expression match is performed on exit. 1812 1813 Direct Field Buffer Manipulation 1814 1815 The chief attribute of a field is its buffer contents. When a form has 1816 been completed, your application usually needs to know the state of 1817 each field buffer. You can find this out with: 1818char *field_buffer(FIELD *field, /* field to query */ 1819 int bufindex); /* number of buffer to query */ 1820 1821 Normally, the state of the zero-numbered buffer for each field is set 1822 by the user's editing actions on that field. It is sometimes useful to 1823 be able to set the value of the zero-numbered (or some other) buffer 1824 from your application: 1825int set_field_buffer(FIELD *field, /* field to alter */ 1826 int bufindex, /* number of buffer to alter */ 1827 char *value); /* string value to set */ 1828 1829 If the field is not large enough and cannot be resized to a 1830 sufficiently large size to contain the specified value, the value will 1831 be truncated to fit. 1832 1833 Calling field_buffer() with a null field pointer will raise an error. 1834 Calling field_buffer() on a field not currently selected for input 1835 will return a correct value. Calling field_buffer() on a field that is 1836 currently selected for input may not necessarily give a correct field 1837 buffer value, because entered data is not necessarily copied to buffer 1838 zero before the exit validation check. To guarantee that the returned 1839 buffer value reflects on-screen reality, call field_buffer() either 1840 (1) in the field's exit validation check routine, (2) from the field's 1841 or form's initialization or termination hooks, or (3) just after a 1842 REQ_VALIDATION request has been processed by the forms driver. 1843 1844 Attributes of Forms 1845 1846 As with field attributes, form attributes inherit a default from a 1847 system default form structure. These defaults can be queried or set by 1848 of these functions using a form-pointer argument of NULL. 1849 1850 The principal attribute of a form is its field list. You can query and 1851 change this list with: 1852int set_form_fields(FORM *form, /* form to alter */ 1853 FIELD **fields); /* fields to connect */ 1854 1855char *form_fields(FORM *form); /* fetch fields of form */ 1856 1857int field_count(FORM *form); /* count connect fields */ 1858 1859 The second argument of set_form_fields() may be a NULL-terminated 1860 field pointer array like the one required by new_form(). In that case, 1861 the old fields of the form are disconnected but not freed (and 1862 eligible to be connected to other forms), then the new fields are 1863 connected. 1864 1865 It may also be null, in which case the old fields are disconnected 1866 (and not freed) but no new ones are connected. 1867 1868 The field_count() function simply counts the number of fields 1869 connected to a given from. It returns -1 if the form-pointer argument 1870 is NULL. 1871 1872 Control of Form Display 1873 1874 In the overview section, you saw that to display a form you normally 1875 start by defining its size (and fields), posting it, and refreshing 1876 the screen. There is an hidden step before posting, which is the 1877 association of the form with a frame window (actually, a pair of 1878 windows) within which it will be displayed. By default, the forms 1879 library associates every form with the full-screen window stdscr. 1880 1881 By making this step explicit, you can associate a form with a declared 1882 frame window on your screen display. This can be useful if you want to 1883 adapt the form display to different screen sizes, dynamically tile 1884 forms on the screen, or use a form as part of an interface layout 1885 managed by panels. 1886 1887 The two windows associated with each form have the same functions as 1888 their analogues in the menu library. Both these windows are painted 1889 when the form is posted and erased when the form is unposted. 1890 1891 The outer or frame window is not otherwise touched by the form 1892 routines. It exists so the programmer can associate a title, a border, 1893 or perhaps help text with the form and have it properly refreshed or 1894 erased at post/unpost time. The inner window or subwindow is where the 1895 current form page is actually displayed. 1896 1897 In order to declare your own frame window for a form, you will need to 1898 know the size of the form's bounding rectangle. You can get this 1899 information with: 1900int scale_form(FORM *form, /* form to query */ 1901 int *rows, /* form rows */ 1902 int *cols); /* form cols */ 1903 1904 The form dimensions are passed back in the locations pointed to by the 1905 arguments. Once you have this information, you can use it to declare 1906 of windows, then use one of these functions: 1907int set_form_win(FORM *form, /* form to alter */ 1908 WINDOW *win); /* frame window to connect */ 1909 1910WINDOW *form_win(FORM *form); /* fetch frame window of form */ 1911 1912int set_form_sub(FORM *form, /* form to alter */ 1913 WINDOW *win); /* form subwindow to connect */ 1914 1915WINDOW *form_sub(FORM *form); /* fetch form subwindow of form */ 1916 1917 Note that curses operations, including refresh(), on the form, should 1918 be done on the frame window, not the form subwindow. 1919 1920 It is possible to check from your application whether all of a 1921 scrollable field is actually displayed within the menu subwindow. Use 1922 these functions: 1923int data_ahead(FORM *form); /* form to be queried */ 1924 1925int data_behind(FORM *form); /* form to be queried */ 1926 1927 The function data_ahead() returns TRUE if (a) the current field is 1928 one-line and has undisplayed data off to the right, (b) the current 1929 field is multi-line and there is data off-screen below it. 1930 1931 The function data_behind() returns TRUE if the first (upper left hand) 1932 character position is off-screen (not being displayed). 1933 1934 Finally, there is a function to restore the form window's cursor to 1935 the value expected by the forms driver: 1936int pos_form_cursor(FORM *) /* form to be queried */ 1937 1938 If your application changes the form window cursor, call this function 1939 before handing control back to the forms driver in order to 1940 re-synchronize it. 1941 1942 Input Processing in the Forms Driver 1943 1944 The function form_driver() handles virtualized input requests for form 1945 navigation, editing, and validation requests, just as menu_driver does 1946 for menus (see the section on menu input handling). 1947int form_driver(FORM *form, /* form to pass input to */ 1948 int request); /* form request code */ 1949 1950 Your input virtualization function needs to take input and then 1951 convert it to either an alphanumeric character (which is treated as 1952 data to be entered in the currently-selected field), or a forms 1953 processing request. 1954 1955 The forms driver provides hooks (through input-validation and 1956 field-termination functions) with which your application code can 1957 check that the input taken by the driver matched what was expected. 1958 1959 Page Navigation Requests 1960 1961 These requests cause page-level moves through the form, triggering 1962 display of a new form screen. 1963 1964 REQ_NEXT_PAGE 1965 Move to the next form page. 1966 1967 REQ_PREV_PAGE 1968 Move to the previous form page. 1969 1970 REQ_FIRST_PAGE 1971 Move to the first form page. 1972 1973 REQ_LAST_PAGE 1974 Move to the last form page. 1975 1976 These requests treat the list as cyclic; that is, REQ_NEXT_PAGE from 1977 the last page goes to the first, and REQ_PREV_PAGE from the first page 1978 goes to the last. 1979 1980 Inter-Field Navigation Requests 1981 1982 These requests handle navigation between fields on the same page. 1983 1984 REQ_NEXT_FIELD 1985 Move to next field. 1986 1987 REQ_PREV_FIELD 1988 Move to previous field. 1989 1990 REQ_FIRST_FIELD 1991 Move to the first field. 1992 1993 REQ_LAST_FIELD 1994 Move to the last field. 1995 1996 REQ_SNEXT_FIELD 1997 Move to sorted next field. 1998 1999 REQ_SPREV_FIELD 2000 Move to sorted previous field. 2001 2002 REQ_SFIRST_FIELD 2003 Move to the sorted first field. 2004 2005 REQ_SLAST_FIELD 2006 Move to the sorted last field. 2007 2008 REQ_LEFT_FIELD 2009 Move left to field. 2010 2011 REQ_RIGHT_FIELD 2012 Move right to field. 2013 2014 REQ_UP_FIELD 2015 Move up to field. 2016 2017 REQ_DOWN_FIELD 2018 Move down to field. 2019 2020 These requests treat the list of fields on a page as cyclic; that is, 2021 REQ_NEXT_FIELD from the last field goes to the first, and 2022 REQ_PREV_FIELD from the first field goes to the last. The order of the 2023 fields for these (and the REQ_FIRST_FIELD and REQ_LAST_FIELD requests) 2024 is simply the order of the field pointers in the form array (as set up 2025 by new_form() or set_form_fields() 2026 2027 It is also possible to traverse the fields as if they had been sorted 2028 in screen-position order, so the sequence goes left-to-right and 2029 top-to-bottom. To do this, use the second group of four 2030 sorted-movement requests. 2031 2032 Finally, it is possible to move between fields using visual directions 2033 up, down, right, and left. To accomplish this, use the third group of 2034 four requests. Note, however, that the position of a form for purposes 2035 of these requests is its upper-left corner. 2036 2037 For example, suppose you have a multi-line field B, and two 2038 single-line fields A and C on the same line with B, with A to the left 2039 of B and C to the right of B. A REQ_MOVE_RIGHT from A will go to B 2040 only if A, B, and C all share the same first line; otherwise it will 2041 skip over B to C. 2042 2043 Intra-Field Navigation Requests 2044 2045 These requests drive movement of the edit cursor within the currently 2046 selected field. 2047 2048 REQ_NEXT_CHAR 2049 Move to next character. 2050 2051 REQ_PREV_CHAR 2052 Move to previous character. 2053 2054 REQ_NEXT_LINE 2055 Move to next line. 2056 2057 REQ_PREV_LINE 2058 Move to previous line. 2059 2060 REQ_NEXT_WORD 2061 Move to next word. 2062 2063 REQ_PREV_WORD 2064 Move to previous word. 2065 2066 REQ_BEG_FIELD 2067 Move to beginning of field. 2068 2069 REQ_END_FIELD 2070 Move to end of field. 2071 2072 REQ_BEG_LINE 2073 Move to beginning of line. 2074 2075 REQ_END_LINE 2076 Move to end of line. 2077 2078 REQ_LEFT_CHAR 2079 Move left in field. 2080 2081 REQ_RIGHT_CHAR 2082 Move right in field. 2083 2084 REQ_UP_CHAR 2085 Move up in field. 2086 2087 REQ_DOWN_CHAR 2088 Move down in field. 2089 2090 Each word is separated from the previous and next characters by 2091 whitespace. The commands to move to beginning and end of line or field 2092 look for the first or last non-pad character in their ranges. 2093 2094 Scrolling Requests 2095 2096 Fields that are dynamic and have grown and fields explicitly created 2097 with offscreen rows are scrollable. One-line fields scroll 2098 horizontally; multi-line fields scroll vertically. Most scrolling is 2099 triggered by editing and intra-field movement (the library scrolls the 2100 field to keep the cursor visible). It is possible to explicitly 2101 request scrolling with the following requests: 2102 2103 REQ_SCR_FLINE 2104 Scroll vertically forward a line. 2105 2106 REQ_SCR_BLINE 2107 Scroll vertically backward a line. 2108 2109 REQ_SCR_FPAGE 2110 Scroll vertically forward a page. 2111 2112 REQ_SCR_BPAGE 2113 Scroll vertically backward a page. 2114 2115 REQ_SCR_FHPAGE 2116 Scroll vertically forward half a page. 2117 2118 REQ_SCR_BHPAGE 2119 Scroll vertically backward half a page. 2120 2121 REQ_SCR_FCHAR 2122 Scroll horizontally forward a character. 2123 2124 REQ_SCR_BCHAR 2125 Scroll horizontally backward a character. 2126 2127 REQ_SCR_HFLINE 2128 Scroll horizontally one field width forward. 2129 2130 REQ_SCR_HBLINE 2131 Scroll horizontally one field width backward. 2132 2133 REQ_SCR_HFHALF 2134 Scroll horizontally one half field width forward. 2135 2136 REQ_SCR_HBHALF 2137 Scroll horizontally one half field width backward. 2138 2139 For scrolling purposes, a page of a field is the height of its visible 2140 part. 2141 2142 Editing Requests 2143 2144 When you pass the forms driver an ASCII character, it is treated as a 2145 request to add the character to the field's data buffer. Whether this 2146 is an insertion or a replacement depends on the field's edit mode 2147 (insertion is the default. 2148 2149 The following requests support editing the field and changing the edit 2150 mode: 2151 2152 REQ_INS_MODE 2153 Set insertion mode. 2154 2155 REQ_OVL_MODE 2156 Set overlay mode. 2157 2158 REQ_NEW_LINE 2159 New line request (see below for explanation). 2160 2161 REQ_INS_CHAR 2162 Insert space at character location. 2163 2164 REQ_INS_LINE 2165 Insert blank line at character location. 2166 2167 REQ_DEL_CHAR 2168 Delete character at cursor. 2169 2170 REQ_DEL_PREV 2171 Delete previous word at cursor. 2172 2173 REQ_DEL_LINE 2174 Delete line at cursor. 2175 2176 REQ_DEL_WORD 2177 Delete word at cursor. 2178 2179 REQ_CLR_EOL 2180 Clear to end of line. 2181 2182 REQ_CLR_EOF 2183 Clear to end of field. 2184 2185 REQ_CLEAR_FIELD 2186 Clear entire field. 2187 2188 The behavior of the REQ_NEW_LINE and REQ_DEL_PREV requests is 2189 complicated and partly controlled by a pair of forms options. The 2190 special cases are triggered when the cursor is at the beginning of a 2191 field, or on the last line of the field. 2192 2193 First, we consider REQ_NEW_LINE: 2194 2195 The normal behavior of REQ_NEW_LINE in insert mode is to break the 2196 current line at the position of the edit cursor, inserting the portion 2197 of the current line after the cursor as a new line following the 2198 current and moving the cursor to the beginning of that new line (you 2199 may think of this as inserting a newline in the field buffer). 2200 2201 The normal behavior of REQ_NEW_LINE in overlay mode is to clear the 2202 current line from the position of the edit cursor to end of line. The 2203 cursor is then moved to the beginning of the next line. 2204 2205 However, REQ_NEW_LINE at the beginning of a field, or on the last line 2206 of a field, instead does a REQ_NEXT_FIELD. O_NL_OVERLOAD option is 2207 off, this special action is disabled. 2208 2209 Now, let us consider REQ_DEL_PREV: 2210 2211 The normal behavior of REQ_DEL_PREV is to delete the previous 2212 character. If insert mode is on, and the cursor is at the start of a 2213 line, and the text on that line will fit on the previous one, it 2214 instead appends the contents of the current line to the previous one 2215 and deletes the current line (you may think of this as deleting a 2216 newline from the field buffer). 2217 2218 However, REQ_DEL_PREV at the beginning of a field is instead treated 2219 as a REQ_PREV_FIELD. 2220 2221 If the O_BS_OVERLOAD option is off, this special action is disabled 2222 and the forms driver just returns E_REQUEST_DENIED. 2223 2224 See Form Options for discussion of how to set and clear the overload 2225 options. 2226 2227 Order Requests 2228 2229 If the type of your field is ordered, and has associated functions for 2230 getting the next and previous values of the type from a given value, 2231 there are requests that can fetch that value into the field buffer: 2232 2233 REQ_NEXT_CHOICE 2234 Place the successor value of the current value in the buffer. 2235 2236 REQ_PREV_CHOICE 2237 Place the predecessor value of the current value in the buffer. 2238 2239 Of the built-in field types, only TYPE_ENUM has built-in successor and 2240 predecessor functions. When you define a field type of your own (see 2241 Custom Validation Types), you can associate our own ordering 2242 functions. 2243 2244 Application Commands 2245 2246 Form requests are represented as integers above the curses value 2247 greater than KEY_MAX and less than or equal to the constant 2248 MAX_COMMAND. If your input-virtualization routine returns a value 2249 above MAX_COMMAND, the forms driver will ignore it. 2250 2251 Field Change Hooks 2252 2253 It is possible to set function hooks to be executed whenever the 2254 current field or form changes. Here are the functions that support 2255 this: 2256typedef void (*HOOK)(); /* pointer to function returning void */ 2257 2258int set_form_init(FORM *form, /* form to alter */ 2259 HOOK hook); /* initialization hook */ 2260 2261HOOK form_init(FORM *form); /* form to query */ 2262 2263int set_form_term(FORM *form, /* form to alter */ 2264 HOOK hook); /* termination hook */ 2265 2266HOOK form_term(FORM *form); /* form to query */ 2267 2268int set_field_init(FORM *form, /* form to alter */ 2269 HOOK hook); /* initialization hook */ 2270 2271HOOK field_init(FORM *form); /* form to query */ 2272 2273int set_field_term(FORM *form, /* form to alter */ 2274 HOOK hook); /* termination hook */ 2275 2276HOOK field_term(FORM *form); /* form to query */ 2277 2278 These functions allow you to either set or query four different hooks. 2279 In each of the set functions, the second argument should be the 2280 address of a hook function. These functions differ only in the timing 2281 of the hook call. 2282 2283 form_init 2284 This hook is called when the form is posted; also, just after 2285 each page change operation. 2286 2287 field_init 2288 This hook is called when the form is posted; also, just after 2289 each field change 2290 2291 field_term 2292 This hook is called just after field validation; that is, just 2293 before the field is altered. It is also called when the form is 2294 unposted. 2295 2296 form_term 2297 This hook is called when the form is unposted; also, just 2298 before each page change operation. 2299 2300 Calls to these hooks may be triggered 2301 1. When user editing requests are processed by the forms driver 2302 2. When the current page is changed by set_current_field() call 2303 3. When the current field is changed by a set_form_page() call 2304 2305 See Field Change Commands for discussion of the latter two cases. 2306 2307 You can set a default hook for all fields by passing one of the set 2308 functions a NULL first argument. 2309 2310 You can disable any of these hooks by (re)setting them to NULL, the 2311 default value. 2312 2313 Field Change Commands 2314 2315 Normally, navigation through the form will be driven by the user's 2316 input requests. But sometimes it is useful to be able to move the 2317 focus for editing and viewing under control of your application, or 2318 ask which field it currently is in. The following functions help you 2319 accomplish this: 2320int set_current_field(FORM *form, /* form to alter */ 2321 FIELD *field); /* field to shift to */ 2322 2323FIELD *current_field(FORM *form); /* form to query */ 2324 2325int field_index(FORM *form, /* form to query */ 2326 FIELD *field); /* field to get index of */ 2327 2328 The function field_index() returns the index of the given field in the 2329 given form's field array (the array passed to new_form() or 2330 set_form_fields()). 2331 2332 The initial current field of a form is the first active field on the 2333 first page. The function set_form_fields() resets this. 2334 2335 It is also possible to move around by pages. 2336int set_form_page(FORM *form, /* form to alter */ 2337 int page); /* page to go to (0-origin) */ 2338 2339int form_page(FORM *form); /* return form's current page */ 2340 2341 The initial page of a newly-created form is 0. The function 2342 set_form_fields() resets this. 2343 2344 Form Options 2345 2346 Like fields, forms may have control option bits. They can be changed 2347 or queried with these functions: 2348int set_form_opts(FORM *form, /* form to alter */ 2349 int attr); /* attribute to set */ 2350 2351int form_opts_on(FORM *form, /* form to alter */ 2352 int attr); /* attributes to turn on */ 2353 2354int form_opts_off(FORM *form, /* form to alter */ 2355 int attr); /* attributes to turn off */ 2356 2357int form_opts(FORM *form); /* form to query */ 2358 2359 By default, all options are on. Here are the available option bits: 2360 2361 O_NL_OVERLOAD 2362 Enable overloading of REQ_NEW_LINE as described in Editing 2363 Requests. The value of this option is ignored on dynamic fields 2364 that have not reached their size limit; these have no last 2365 line, so the circumstances for triggering a REQ_NEXT_FIELD 2366 never arise. 2367 2368 O_BS_OVERLOAD 2369 Enable overloading of REQ_DEL_PREV as described in Editing 2370 Requests. 2371 2372 The option values are bit-masks and can be composed with logical-or in 2373 the obvious way. 2374 2375 Custom Validation Types 2376 2377 The form library gives you the capability to define custom validation 2378 types of your own. Further, the optional additional arguments of 2379 set_field_type effectively allow you to parameterize validation types. 2380 Most of the complications in the validation-type interface have to do 2381 with the handling of the additional arguments within custom validation 2382 functions. 2383 2384 Union Types 2385 2386 The simplest way to create a custom data type is to compose it from 2387 two preexisting ones: 2388FIELD *link_fieldtype(FIELDTYPE *type1, 2389 FIELDTYPE *type2); 2390 2391 This function creates a field type that will accept any of the values 2392 legal for either of its argument field types (which may be either 2393 predefined or programmer-defined). If a set_field_type() call later 2394 requires arguments, the new composite type expects all arguments for 2395 the first type, than all arguments for the second. Order functions 2396 (see Order Requests) associated with the component types will work on 2397 the composite; what it does is check the validation function for the 2398 first type, then for the second, to figure what type the buffer 2399 contents should be treated as. 2400 2401 New Field Types 2402 2403 To create a field type from scratch, you need to specify one or both 2404 of the following things: 2405 * A character-validation function, to check each character as it is 2406 entered. 2407 * A field-validation function to be applied on exit from the field. 2408 2409 Here is how you do that: 2410typedef int (*HOOK)(); /* pointer to function returning int */ 2411 2412FIELDTYPE *new_fieldtype(HOOK f_validate, /* field validator */ 2413 HOOK c_validate) /* character validator */ 2414 2415int free_fieldtype(FIELDTYPE *ftype); /* type to free */ 2416 2417 At least one of the arguments of new_fieldtype() must be non-NULL. The 2418 forms driver will automatically call the new type's validation 2419 functions at appropriate points in processing a field of the new type. 2420 2421 The function free_fieldtype() deallocates the argument fieldtype, 2422 freeing all storage associated with it. 2423 2424 Normally, a field validator is called when the user attempts to leave 2425 the field. Its first argument is a field pointer, from which it can 2426 get to field buffer 0 and test it. If the function returns TRUE, the 2427 operation succeeds; if it returns FALSE, the edit cursor stays in the 2428 field. 2429 2430 A character validator gets the character passed in as a first 2431 argument. It too should return TRUE if the character is valid, FALSE 2432 otherwise. 2433 2434 Validation Function Arguments 2435 2436 Your field- and character- validation functions will be passed a 2437 second argument as well. This second argument is the address of a 2438 structure (which we will call a pile) built from any of the 2439 field-type-specific arguments passed to set_field_type(). If no such 2440 arguments are defined for the field type, this pile pointer argument 2441 will be NULL. 2442 2443 In order to arrange for such arguments to be passed to your validation 2444 functions, you must associate a small set of storage-management 2445 functions with the type. The forms driver will use these to synthesize 2446 a pile from the trailing arguments of each set_field_type() argument, 2447 and a pointer to the pile will be passed to the validation functions. 2448 2449 Here is how you make the association: 2450typedef char *(*PTRHOOK)(); /* pointer to function returning (char *) */ 2451typedef void (*VOIDHOOK)(); /* pointer to function returning void */ 2452 2453int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */ 2454 PTRHOOK make_str, /* make structure from args */ 2455 PTRHOOK copy_str, /* make copy of structure */ 2456 VOIDHOOK free_str); /* free structure storage */ 2457 2458 Here is how the storage-management hooks are used: 2459 2460 make_str 2461 This function is called by set_field_type(). It gets one 2462 argument, a va_list of the type-specific arguments passed to 2463 set_field_type(). It is expected to return a pile pointer to a 2464 data structure that encapsulates those arguments. 2465 2466 copy_str 2467 This function is called by form library functions that allocate 2468 new field instances. It is expected to take a pile pointer, 2469 copy the pile to allocated storage, and return the address of 2470 the pile copy. 2471 2472 free_str 2473 This function is called by field- and type-deallocation 2474 routines in the library. It takes a pile pointer argument, and 2475 is expected to free the storage of that pile. 2476 2477 The make_str and copy_str functions may return NULL to signal 2478 allocation failure. The library routines will that call them will 2479 return error indication when this happens. Thus, your validation 2480 functions should never see a NULL file pointer and need not check 2481 specially for it. 2482 2483 Order Functions For Custom Types 2484 2485 Some custom field types are simply ordered in the same well-defined 2486 way that TYPE_ENUM is. For such types, it is possible to define 2487 successor and predecessor functions to support the REQ_NEXT_CHOICE and 2488 REQ_PREV_CHOICE requests. Here is how: 2489typedef int (*INTHOOK)(); /* pointer to function returning int */ 2490 2491int set_fieldtype_arg(FIELDTYPE *type, /* type to alter */ 2492 INTHOOK succ, /* get successor value */ 2493 INTHOOK pred); /* get predecessor value */ 2494 2495 The successor and predecessor arguments will each be passed two 2496 arguments; a field pointer, and a pile pointer (as for the validation 2497 functions). They are expected to use the function field_buffer() to 2498 read the current value, and set_field_buffer() on buffer 0 to set the 2499 next or previous value. Either hook may return TRUE to indicate 2500 success (a legal next or previous value was set) or FALSE to indicate 2501 failure. 2502 2503 Avoiding Problems 2504 2505 The interface for defining custom types is complicated and tricky. 2506 Rather than attempting to create a custom type entirely from scratch, 2507 you should start by studying the library source code for whichever of 2508 the pre-defined types seems to be closest to what you want. 2509 2510 Use that code as a model, and evolve it towards what you really want. 2511 You will avoid many problems and annoyances that way. The code in the 2512 ncurses library has been specifically exempted from the package 2513 copyright to support this. 2514 2515 If your custom type defines order functions, have do something 2516 intuitive with a blank field. A useful convention is to make the 2517 successor of a blank field the types minimum value, and its 2518 predecessor the maximum. 2519