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