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