Graphics Plus

home *** CD-ROM | disk | FTP | other *** search

/ Graphics Plus / Graphics Plus.iso / msdos / animutil / fastgfx / fg303b / manuals.arj / USER14.DOC < prev next >

Wrap

Text File | 1993-10-02 | 66.7 KB | 1,430 lines

Chapter 14 Input Device Support 260 Fastgraph User's Guide Overview The selection of application input devices is an important part of designing a program for the IBM PC and PS/2 family of systems. The keyboard and mouse are the most popular, and in fact more and more applications, especially those that use a graphical interface, actually require a mouse to use the product. Another input device, primarily used in entertainment software, is the joystick. Although not as popular as the mouse, joysticks nevertheless can simplify the use of certain applications. Fastgraph provides support for these three types of input devices, and this chapter will discuss this in detail. Keyboard Support Fastgraph's keyboard support includes routines to read keystrokes, check the state of certain keys, and set the state of these keys. In addition, Fastgraph provides a low-level keyboard handler that replaces the BIOS keyboard handler to increase keyboard responsiveness. These routines are independent of the other parts of Fastgraph and thus do not require that you call fg_setmode. All keyboard-related routines work in text and graphics video modes. The IBM PC and PS/2 keyboards produce two types of character codes -- standard codes and extended codes (extended codes are sometimes called auxiliary codes). The standard codes correspond to the 128 characters in the ASCII character set. In general, pressing keys on the main part of the keyboard, or on the numeric keypad with NumLock turned on, will generate a standard code. The 128 extended codes are specific to the IBM PC and PS/2 keyboards. Some common keystrokes that produce extended codes are keys on the numeric keypad with NumLock turned off, the function keys, or pressing Alt with another key. The following tables show the standard and extended keyboard codes. Table of standard keyboard codes key code key code key code key code (none) 0 space 32 @ 64 ` 96 Ctrl+A 1 ! 33 A 65 a 97 Ctrl+B 2 " 34 B 66 b 98 Ctrl+C 3 # 35 C 67 c 99 Ctrl+D 4 $ 36 D 68 d 100 Ctrl+E 5 % 37 E 69 e 101 Ctrl+F 6 & 38 F 70 f 102 Ctrl+G 7 ' 39 G 71 g 103 Ctrl+H 8 ( 40 H 72 h 104 Ctrl+I 9 ) 41 I 73 i 105 Ctrl+J 10 * 42 J 74 j 106 Ctrl+K 11 + 43 K 75 k 107 Ctrl+L 12 , 44 L 76 l 108 Ctrl+M 13 - 45 M 77 m 109 Ctrl+N 14 . 46 N 78 n 110 Ctrl+O 15 / 47 O 79 o 111 Ctrl+P 16 0 48 P 80 p 112 Ctrl+Q 17 1 49 Q 81 q 113 Chapter 14: Input Device Support 261 Ctrl+R 18 2 50 R 82 r 114 Ctrl+S 19 3 51 S 83 s 115 Ctrl+T 20 4 52 T 84 t 116 Ctrl+U 21 5 53 U 85 u 117 Ctrl+V 22 6 54 V 86 v 118 Ctrl+W 23 7 55 W 87 w 119 Ctrl+X 24 8 56 X 88 x 120 Ctrl+Y 25 9 57 Y 89 y 121 Ctrl+Z 26 : 58 Z 90 z 122 Ctrl+[ 27 ; 59 [ 91 { 123 Ctrl+\ 28 < 60 \ 92 | 124 Ctrl+] 29 = 61 ] 93 } 125 Ctrl+^ 30 > 62 ^ 94 ~ 126 Ctrl+- 31 ? 63 _ 95 Ctrl+BS 127 Table of extended keyboard codes code key 3 Ctrl+@ 15 Shift+Tab (back tab) 16-25 Alt+Q to Alt+P (top row of letters) 30-38 Alt+A to Alt+L (middle row of letters) 44-50 Alt+Z to Alt+M (bottom row of letters) 59-68 F1 to F10 71 Home 72 up arrow 73 PgUp 75 left arrow 77 right arrow 79 End 80 down arrow 81 PgDn 82 Ins 83 Del 84-93 Shift+F1 to Shift+F10 94-103 Ctrl+F1 to Ctrl+F10 104-113 Alt+F1 to Alt+F10 114 Ctrl+PrtSc 115 Ctrl+left arrow 116 Ctrl+right arrow 117 Ctrl+End 118 Ctrl+PgDn 119 Ctrl+Home 120-131 Alt+1 to Alt+= (top row of keys) 132 Ctrl+PgUp In addition, four keys generate the same standard codes as other control key combinations. These keys are: key same as code Backspace Ctrl+H 8 Tab Ctrl+I 9 Enter Ctrl+M 13 Escape Ctrl+[ 27 262 Fastgraph User's Guide The CapsLock, NumLock, and ScrollLock keys do not generate a standard or extended code when pressed. Instead, they toggle between off and on states. Reading Keystrokes When you press a key or key combination, the standard or extended code representing that keystroke is stored in the ROM BIOS keyboard buffer. This buffer can hold up to 16 keystrokes and thus provides a type-ahead capability. Fastgraph includes three routines for reading keystroke information from the keyboard buffer. The fg_getkey routine reads the next item in the keyboard buffer if one is available (that is, if a key has been pressed). If the keyboard buffer is empty (meaning no key has been pressed), fg_getkey waits for a keystroke and then reports information about it. Another routine, fg_intkey, reads the next keystroke from the keyboard buffer if one is available. If the keyboard buffer is empty, fg_intkey immediately returns and reports this condition. The fg_intkey routine is useful when a program must continue performing a task until a key is pressed. We've already seen the third routine, fg_waitkey, which flushes the keyboard buffer and then waits for another keystroke. Unlike fg_getkey and fg_intkey, fg_waitkey does not return any keystroke information. It is most useful in "press any key to continue" situations. Both fg_getkey and fg_intkey require two one-byte arguments passed by reference. If the keystroke is represented by a standard keyboard code, fg_getkey and fg_intkey return its code in the first argument and set the second argument to zero. Similarly, if the keystroke generates an extended code, the routines return its code in the second argument and set the first argument to zero. If the fg_intkey routine detects an empty keyboard buffer, it sets both arguments to zero. Example 14-1 is a simple program that uses the fg_getkey routine. It solicits keystrokes and then displays the two values returned by fg_getkey, one of which will always be zero. The variable key receives the key's standard code, while aux receives its extended code. Note that fg_getkey is the only Fastgraph routine in the program; this can be done because the keyboard support routines are logically independent from the rest of Fastgraph. The program returns to DOS when you press the Escape key. Example 14-1. #include <fastgraf.h> #include <stdio.h> void main(void); #define ESC 27 void main() { unsigned char key, aux; do { fg_getkey(&key,&aux); printf("key = %3d aux = %3d\n",key,aux); } Chapter 14: Input Device Support 263 while (key != ESC); } Example 14-2 reads keystrokes using the fg_intkey routine at half-second intervals (18 fg_waitfor units equals one second). As in the previous example, the program displays the standard and extended codes for each keystroke. However, example 14-2 will continuously execute the while loop even if no keystrokes are available, in which case the key and aux values will both be zero. The program returns to DOS when you press the Escape key. Example 14-2. #include <fastgraf.h> #include <stdio.h> void main(void); #define ESC 27 void main() { unsigned char key, aux; do { fg_waitfor(9); fg_intkey(&key,&aux); printf("key = %3d aux = %3d\n",key,aux); } while (key != ESC); } When you use fg_intkey in a "tight" loop that does little else, you should force a small delay within the loop by calling fg_waitfor as in example 14-2. Typically a delay of one or two clock ticks is enough. Without this delay, the BIOS may not be able to handle all keyboard activity, and thus some keystrokes may not be available to your program. Testing and Setting Key States As mentioned earlier, the CapsLock, NumLock, and ScrollLock keys do not generate a standard or extended code when pressed but instead toggle between off and on states. Fastgraph includes routines for checking the state of these keys, as well as setting the state of the CapsLock and NumLock keys. The Fastgraph routines fg_capslock, fg_numlock, and fg_scrlock respectively read the state of the CapsLock, NumLock, and ScrollLock keys. Each routine has no arguments and returns the key state as its function value. A return value of 0 means the associated key is in the off state, while 1 indicates the key is in the on state. If the keyboard does not have a ScrollLock key, fg_scrlock considers the key off and returns a value of zero. Example 14-3 is a simple program that uses the fg_capslock, fg_numlock, and fg_scrlock routines to print messages describing the current state of these three keys. 264 Fastgraph User's Guide Example 14-3. #include <fastgraf.h> #include <stdio.h> void main(void); void main() { if (fg_capslock()) printf("CapsLock is on.\n"); else printf("CapsLock is off.\n"); if (fg_numlock()) printf("NumLock is on.\n"); else printf("NumLock is off.\n"); if (fg_scrlock()) printf("ScrollLock is on.\n"); else printf("ScrollLock is off.\n"); } You also can set the state of the CapsLock and NumLock keys within a program. Fastgraph includes two routines, fg_setcaps and fg_setnum, for this purpose. Each routine requires an integer argument that specifies the new key state. If the argument value is 0, the key will be turned off; if the value is 1, the key will be turned on. Example 14-4 uses fg_setcaps and fg_setnum to turn off CapsLock and NumLock. Example 14-4. #include <fastgraf.h> void main(void); void main() { fg_setcaps(0); fg_setnum(0); } On most keyboards, changing key states with fg_setcaps or fg_setnum also will change the keyboard state light to reflect the new key state. However, some older keyboards, especially when used on PC, PC/XT, or Tandy 1000 systems, do not update the state light. This makes the state light inconsistent with the true key state. Low-Level Keyboard Handler Fastgraph includes a low-level keyboard handler that replaces the BIOS keyboard handler. The replacement handler intercepts keystrokes ahead of the BIOS and thus eliminates the annoying beep that sounds upon filling the BIOS Chapter 14: Input Device Support 265 keyboard buffer. Fastgraph's keyboard handler is especially well-suited to game development because it increases keyboard responsiveness in high-speed action games. However, when the low-level keyboard handler is enabled, it is not possible to use fg_getkey, fg_intkey, fg_waitkey, or any third party functions that use BIOS or DOS services for keyboard activity. For this reason, a program that enables the low-level keyboard handler must disable it before exiting to DOS. The low-level keyboard handler can be enabled and disabled at any time. The fg_kbinit routine is provided for this purpose. To enable Fastgraph's low-level keyboard handler, pass the value 1 to fg_kbinit. To disable Fastgraph's handler and re-enable the BIOS keyboard handler, pass the value zero. No harm is caused if you try to enable Fastgraph's keyboard handler when it is already active, or if you try to disable it when the BIOS handler is active. When the low-level keyboard handler is enabled, you can use the fg_kbtest routine to check if keys are currently pressed or released. This routine provides the only mechanism for accessing the keyboard when the low- level handler is enabled. It specifies the keys through the use of scan codes. If the corresponding key is pressed, fg_kbtest returns 1. If it is released, the routine returns zero. The following table lists the scan codes returned by pressing the keys on a standard PC keyboard. Table of scan codes scan scan scan scan key code key code key code key code Esc 1 I 23 X 45 F9 67 1 2 O 24 C 46 F10 68 2 3 P 25 V 47 NumLock 69 3 4 [ 26 B 48 ScrLock 70 4 5 ] 27 N 49 Home 71 5 6 Enter 28 M 50 Up arrow 72 6 7 Ctrl 29 , 51 PgUp 73 7 8 A 30 . 52 KP- 74 8 9 S 31 / 53 L arrow 75 9 10 D 32 R shift 54 KP5 76 0 11 F 33 KP* 55 R arrow 77 - 12 G 34 Alt 56 KP+ 78 = 13 H 35 Space 57 End 79 BS 14 J 36 CapsLock 58 Dn arrow 80 Tab 15 K 37 F1 59 PgDn 81 Q 16 L 38 F2 60 Ins 82 W 17 ; 39 F3 61 Del 83 E 18 ' 40 F4 62 (unused) 84 R 19 ` 41 F5 63 (unused) 85 T 20 L shift 42 F6 64 (unused) 86 Y 21 \ 43 F7 65 F11 87 U 22 Z 44 F8 66 F12 88 There are actually more scan codes defined for PC keyboards than listed in this table. Such scan codes are generated when a key is pressed as a combination of one or more keys, such as when the shift and slash keys are pressed together to produce a question mark (?) character. Fastgraph's low- 266 Fastgraph User's Guide level keyboard handler is designed to report the pressing or releasing of keys themselves, as opposed to reporting the actual characters so produced. It is thus not possible for the keyboard handler to report the scan code for a multi-key character. If needed, such characters can be identified by the scan codes generated for each individual key in the sequence. For example, a question mark character would be reported as a forward slash (scan code 53) generated while pressing the left shift (42) or right shift (54) keys. Example 14-5 illustrates the use of Fastgraph's low-level keyboard handler. It first uses fg_kbinit to enable Fastgraph's keyboard handler and displays a message stating this. Then, at approximately one second intervals, the program calls fg_kbtest to check which of the four arrow keys are pressed and displays an appropriate message. Pressing Escape restores the BIOS keyboard handler and exits to DOS. Example 14-5. #include <fastgraf.h> #include <stdio.h> void main(void); #define ESC 1 #define LEFT 75 #define RIGHT 77 #define UP 72 #define DOWN 80 void main() { fg_kbinit(1); printf("Keyboard handler enabled.\n"); do { printf("keys pressed: "); if (fg_kbtest(LEFT)) printf("Left "); if (fg_kbtest(RIGHT)) printf("Right "); if (fg_kbtest(UP)) printf("Up "); if (fg_kbtest(DOWN)) printf("Down "); printf("\n"); fg_waitfor(18); } while (fg_kbtest(ESC) == 0); fg_kbinit(0); printf("Keyboard handler disabled.\n"); } Mouse Support The mouse is a very popular input and pointing device, especially in graphically-oriented programs. Fastgraph contains several routines to support mice. These routines perform such tasks as mouse initialization, controlling and defining the mouse cursor, and reporting information about the mouse position and button status. The underlying software that controls the mouse is called the mouse driver. Fastgraph's mouse support routines provide a high-level interface to Chapter 14: Input Device Support 267 this driver. The Microsoft Mouse and its accompanying mouse driver have become an industry standard, and other manufacturers of mice have also made their mouse drivers Microsoft compatible. For this reason, the Fastgraph mouse support routines assume you are using a Microsoft or compatible mouse driver. Unfortunately, not all mouse drivers are created equal. That is, some drivers are not Microsoft compatible, even though they may be advertised as such. In some cases, these incompatibilities are rather trivial, but others are significant. For example, early versions of some third party mouse drivers had real problems in the EGA graphics modes. The Microsoft mouse driver, the Logitech mouse driver (version 3.2 or above), and the DFI mouse driver (version 3.00 or above) are known to work well with Fastgraph's mouse support routines. Any other Microsoft compatible mouse driver also should work properly. Initializing the Mouse There are two steps required to use Fastgraph's mouse support routines within an application program. First, you must install the mouse driver. This is done before running the application, typically by entering the command MOUSE at the DOS command prompt. Second, you must use the Fastgraph routine fg_mouseini to initialize the mouse within the program. The fg_mouseini routine has no arguments and returns a "success or failure" indicator as its function value. If the return value is -1, it means fg_mouseini could not initialize the mouse (either because the mouse driver is not installed, or the driver is installed but the mouse is physically disconnected). If fg_mouseini returns a positive integer value, the mouse initialization was successful. The value itself indicates the number of buttons (either 2 or 3) on the mouse. If you don't call fg_mouseini, or if fg_mouseini can't initialize the mouse, none of Fastgraph's other mouse support routines will have any effect.3 Example 14-6 illustrates how to initialize the mouse. Unlike the keyboard support routines, Fastgraph's mouse support routines require that fg_setmode be called first. In this example, we simply pass fg_setmode the value -1 to initialize Fastgraph for whatever video mode is in effect when we run the program. The program then calls fg_mouseini and prints a message indicating whether or not the initialization was successful. If it was, the message includes the number of buttons on the mouse. Example 14-6. #include <fastgraf.h> #include <stdio.h> void main(void); void main() { ____________________ (3) If you use another mouse library or communicate directly with the mouse driver, you must still call fg_mouseini if your program runs in modes 13 through 18. Otherwise, Fastgraph won't know that your program is using a mouse and may display graphics incorrectly. 268 Fastgraph User's Guide int status; fg_setmode(-1); status = fg_mouseini(); if (status < 0) printf("Mouse not available.\n"); else printf("%d button mouse found.\n",status); } You should be aware that certain mouse drivers do not fully initialize the mouse when a program changes video modes. This problem most frequently occurs when you restore the original video mode at the end of a program that has called fg_mouseini. When changing video modes, you must first make the mouse cursor invisible (this is described in the next section), change the video mode, and then call fg_mouseini again to initialize the mouse for the new video mode. XVGA and SVGA Mouse Considerations Mouse drivers do not have the ability to directly display the mouse cursor in XVGA and SVGA graphics modes (modes 20 to 29). Hence, Fastgraph must display the mouse cursor through an interrupt handler that is activated whenever the mouse moves. The handler is automatically installed when you call fg_mouseini in modes 20 to 29. If you do not disable this handler before your program exits, it will remain "hooked" to the mouse driver. This will most likely hang your system the next time you try doing anything of consequence. The fg_mousefin routine removes Fastgraph's mouse interrupt handler from the mouse driver. In XVGA and SVGA graphics modes, you should call fg_mousefin just before restoring the original video mode, as illustrated below: fg_mousefin(); fg_setmode(old_mode); fg_reset(); Again, calling fg_mousefin is required only in XVGA and SVGA graphics modes. Calling it in other video modes is not applicable, though it causes no problems. In the standard VGA/MCGA 256-color mode (mode 19), white pixels in the mouse cursor are displayed in color 15. This is inconsistent with other graphics modes, where the mouse cursor's white pixels are displayed in the highest-numbered color value available in that mode. Fastgraph corrects this inconsistency in XVGA and SVGA 256-color graphics modes by displaying white mouse cursor pixels in color 255. Like color 15, color 255 is white by default. This allows you to redefine color 15 in your 256-color applications without interfering with the mouse cursor colors. Chapter 14: Input Device Support 269 Controlling the Mouse Cursor The mouse cursor indicates the current position of the mouse. By default, the cursor is a small white arrow in graphics modes and a one- character rectangle in text modes. After you use fg_mouseini to initialize the mouse, the mouse cursor is invisible. To make it visible, you must use the fg_mousevis routine. This routine has a single integer argument that defines the mouse cursor visibility. If it is 0, the mouse cursor will be invisible; if it is 1, the mouse cursor becomes visible. If the mouse cursor is in an area of the screen that is being updated, or if it moves into this area during the update process, you must make the mouse cursor invisible. Additionally, when performing any video output in the native EGA and VGA graphics modes (modes 13 through 18), you also must make the mouse cursor invisible. Instead of checking for these conditions, it is more convenient and efficient to make the mouse cursor invisible during all screen updates and then make it visible again when the updating is finished. Finally, you must make the mouse cursor invisible whenever you change the visual page number with fg_setvpage. After you initialize the mouse, the cursor is positioned in the center of the screen. Moving the mouse of course changes the cursor position, but you also can position the mouse cursor with the Fastgraph routine fg_mousemov. This routine has two arguments that specify the new horizontal and vertical cursor position. The position is expressed in screen space units for graphics modes, while it is expressed in character cells for text modes. The fg_mousemov routine moves the cursor whether or not it is visible. Sometimes it is useful to restrict the mouse cursor to a specific area of the screen. The Fastgraph routine fg_mouselim prevents the mouse cursor from moving outside the specified rectangular area. It requires four arguments that specify the minimum horizontal coordinate, maximum horizontal coordinate, minimum vertical coordinate, and maximum vertical coordinate of this area. Again, the coordinates are expressed in screen space units for graphics modes and character cells for text modes. One of the most important functions of the mouse driver is to translate the horizontal and vertical mouse movements into a position on the screen. The mouse reports these movements to the mouse driver in units called mickeys (one mickey is about 1/200 of an inch). By default, moving the mouse 8 mickeys in the horizontal direction moves the mouse cursor one horizontal pixel. Similarly, moving the mouse 16 mickeys vertically moves the cursor one vertical pixel. Fastgraph provides a routine named fg_mousespd that can change these values, which effectively allows you to control the speed at which the mouse cursor moves relative to the movement of the mouse itself. The fg_mousespd routine requires two arguments that define the number of mickeys required for eight pixels of mouse cursor movement. The first argument specifies this for the horizontal direction, and the second for the vertical direction. Example 14-7, which runs in any graphics mode, demonstrates the fg_mousevis, fg_mousemov, fg_mouselim, and fg_mousespd routines. The program first establishes the video mode, initializes the mouse, and fills the screen with a white rectangle. Next, the program calls fg_mousevis to make the mouse cursor visible and then calls fg_mouselim to restrict the mouse cursor 270 Fastgraph User's Guide to an area one-fourth the size of the screen, centered in the middle of the screen. At this point you should move the mouse cursor around the screen to see the effect of fg_mouselim and note the speed at which the cursor moves relative to the mouse itself. The program continues when you press any key. The program then uses fg_mousemov to move the mouse cursor to each corner of the region established by fg_mouselim. The call to fg_waitfor keeps the cursor in each corner for two seconds, unless you move the mouse. Note how the program tries to move the mouse cursor to each corner of the screen, but since doing so would move the cursor outside the defined region of movement, fg_mousemov just positions the cursor at the nearest point possible within this region. The last call to fg_mousemov moves the cursor back to the middle of the screen. After doing this, the program calls fg_mousespd to change the mouse cursor speed. The values passed to fg_mousespd (16 and 32) are twice the defaults and therefore make you move the mouse twice as far as before to move the mouse cursor the same distance. When you run the program, compare the mouse sensitivity to the original speed. After a keystroke, the program returns to DOS. Example 14-7. #include <fastgraf.h> #include <stdio.h> #include <stdlib.h> void main(void); void main() { int maxx, maxy; int old_mode; old_mode = fg_getmode(); fg_setmode(fg_automode()); if (fg_mouseini() < 0) { fg_setmode(old_mode); fg_reset(); exit(1); } maxx = fg_getmaxx(); maxy = fg_getmaxy(); fg_setcolor(15); fg_rect(0,maxx,0,maxy); fg_mousevis(1); fg_mouselim(maxx/4,3*maxx/4,maxy/4,3*maxy/4); fg_waitkey(); fg_mousemov(0,0); fg_waitfor(36); fg_mousemov(maxx,0); fg_waitfor(36); fg_mousemov(maxx,maxy); fg_waitfor(36); fg_mousemov(0,maxy); fg_waitfor(36); Chapter 14: Input Device Support 271 fg_mousemov(maxx/2,maxy/2); fg_mousespd(16,32); fg_waitkey(); fg_setmode(old_mode); fg_reset(); } Reporting the Mouse Status It is obviously important to be able to track the mouse position and button status. The Fastgraph routines fg_mousepos and fg_mousebut enable you to do this. The fg_mousepos routine returns information about the current mouse cursor position and button status. It requires three integer arguments, all passed by reference. The first two arguments respectively receive the horizontal and vertical coordinates of the mouse cursor. These values are expressed in screen space units for graphics modes and character cells for text modes. The third argument receives a three-bit mask containing the button status as indicated below. bit number meaning 0 1 if left button pressed, 0 if not 1 1 if right button pressed, 0 if not 2 1 if middle button pressed, 0 if not For example, if both the left and right buttons are pressed, the button status will be set to 3. If the mouse only has two buttons, bit 2 will always be zero. Another routine, fg_mousebut, is available for returning the number of button press or release counts that have occurred since the last check, or since calling fg_mouseini. Each mouse button maintains its own separate counters, so fg_mousebut returns this information for a specific button. Additionally, fg_mousebut returns the horizontal and vertical position of the mouse cursor at the time the specified button was last pressed or released. The fg_mousebut routine takes four integer arguments, of which the last three are passed by reference. The first argument specifies the button of interest (1 means the left button, 2 is the right button, and 3 is the middle button). If this value is positive, button press counts will be reported. If it is negative, release counts will be reported. The second, third, and fourth arguments respectively receive the press or release count, the horizontal mouse cursor position at the time of the last press or release, and the vertical position at that same time. If the press or release count is zero, the mouse cursor position is returned as (0,0). The coordinate positions are expressed in screen space units for graphics modes and character cells for text modes. Example 14-8 runs in any graphics video mode and illustrates the use of the fg_mousepos and fg_mousebut routines. The program first establishes the video mode and then initializes the mouse (the program exits if the 272 Fastgraph User's Guide initialization fails). It next fills the entire screen with a white rectangle and then calls fg_mousevis to make the mouse cursor visible. The main part of example 14-8 is a while loop that polls the mouse at three-second intervals (the call fg_waitfor(54) delays the program for three seconds). Within the loop, the program first uses fg_mousebut to get the number of times the left mouse button was pressed in the last three seconds. Following this, the fg_mousepos routine gets the current mouse position. The program then displays this information in the upper left corner of the screen; note how fg_mousevis is used to make the cursor invisible during graphics operations. The program continues until you press the right mouse button, checked by the call to fg_mousebut at the end of the loop. Example 14-8. #include <fastgraf.h> #include <stdio.h> #include <stdlib.h> void main(void); void main() { int old_mode; int buttons, count; int x, y; char string[25]; old_mode = fg_getmode(); fg_setmode(fg_automode()); if (fg_mouseini() < 0) { fg_setmode(old_mode); fg_reset(); exit(1); } fg_setcolor(15); fg_rect(0,fg_getmaxx(),0,fg_getmaxy()); fg_mousevis(1); do { fg_waitfor(54); fg_mousebut(1,&count,&x,&y); fg_mousepos(&x,&y,&buttons); sprintf(string,"X=%3d Y=%3d count=%4d",x,y,count); fg_mousevis(0); fg_setcolor(15); fg_rect(0,fg_xconvert(25),0,fg_yconvert(1)); fg_setcolor(0); fg_locate(0,0); fg_text(string,24); fg_mousevis(1); fg_mousebut(2,&count,&x,&y); } while (count == 0); fg_setmode(old_mode); Chapter 14: Input Device Support 273 fg_reset(); } Defining the Mouse Cursor By default, the mouse cursor is a small white arrow in graphics modes and a one-character rectangle in text modes. In graphics modes, you can change the mouse cursor to any 16 by 16 pixel image with the Fastgraph routine fg_mouseptr (in the CGA four-color graphics modes, the cursor size is 8 by 16 pixels). You cannot change the mouse cursor shape in text modes, but you can use the Fastgraph routine fg_mousecur to define how it interacts with existing characters on the screen. Text Modes To change the mouse cursor in text modes, you must first define two 16- bit quantities called the screen mask and cursor mask. The following figure defines the format of each mask. bits meaning 0 to 7 ASCII character value 8 to 11 foreground color 12 to 14 background color 15 blink Notice how this structure parallels the character and attribute bytes associated with each character cell. The default screen mask is 77FF hex, and the default cursor mask is 7700 hex. When you position the mouse over a specific character cell, the mouse driver uses the current screen and cursor masks to determine the mouse cursor's appearance. First, the mouse driver logically ANDs the screen mask with the existing contents of that character cell. It then XORs that result with the cursor mask to display the mouse cursor. For example, consider how the mouse cursor is produced in the 80-column color text mode (mode 3). Suppose a specific character cell contains the ASCII character 0 (48 decimal, 30 hex) and an attribute byte that specifies a white (color 15) foreground on a blue background (color 1) and does not blink (blink bit 0). The binary structure of the character and its attribute are: attribute character 0 001 1111 00110000 Now let's see what happens when we apply the screen and cursor masks to the character and its attribute. attribute/character 0001 1111 0011 0000 (1F30 hex) default screen mask 0111 0111 1111 1111 (77FF hex) ------------------- result of AND 0001 0111 0011 0000 (1730 hex) 274 Fastgraph User's Guide default cursor mask 0111 0111 0000 0000 (7700 hex) ------------------- result of XOR 0110 0000 0011 0000 (6030 hex) The resulting character (30 hex) is the original character, but the new attribute (60 hex) represents a black foreground with a brown background and does not blink. As long as the mouse cursor remains positioned on this character cell, it would appear black on brown. When we use the default screen and cursor masks, the mouse cursor will always display the original character and it will not blink. The cursor foreground color will be 15-F, where F is the displayed character's foreground color. Similarly, the cursor background color will be 7-B, where B is the displayed character's background color. The default masks will virtually always produce a satisfactory mouse cursor. It is possible, however, to change the appearance of the mouse cursor in text modes by using your own screen and cursor masks. The Fastgraph routine fg_mousecur does just that. It expects two arguments, the first being the cursor mask and the second the screen mask. Example 14-9 demonstrates the use of fg_mousecur. The program displays some text and uses the default mouse cursor. After waiting for a keystroke, the program calls fg_mousecur to define a new mouse cursor. The new cursor is similar to the default cursor, but it displays the foreground colors in the opposite intensity as the default cursor. The program then waits for another keystroke before returning to DOS. Example 14-9. #include <fastgraf.h> #include <stdio.h> #include <stdlib.h> void main(void); void main() { int old_mode; int row; old_mode = fg_getmode(); fg_setmode(3); if (fg_mouseini() < 0) { fg_setmode(old_mode); fg_reset(); exit(1); } fg_setattr(7,0,0); fg_rect(0,fg_getmaxx(),0,fg_getmaxy()); fg_setattr(12,7,0); for (row = 0; row < 25; row++) { fg_locate(row,34); fg_text("example 14-9",12); } Chapter 14: Input Device Support 275 fg_mousevis(1); fg_waitkey(); fg_mousecur(0x7FFF,0x7F00); fg_waitkey(); fg_setmode(old_mode); fg_reset(); } Graphics Modes Defining the mouse cursor in graphics video modes also requires creating a screen mask and cursor mask, but as one might expect, the structure of these masks is vastly different from for text modes. In fact, it closely resembles the mode-independent bit map format used by the fg_drawmap routine. Although their structure differs, the way the mouse driver applies the masks is the same as in the text modes. That is, the driver displays the mouse cursor by first logically ANDing video memory with the screen mask, and then XORing that result with the cursor mask. Let's begin by looking at the masks for the default mouse cursor in graphics modes. The size of each mask (and hence the mouse cursor) is 16 pixels wide and 16 pixels high. As mentioned earlier, the default cursor is a small white arrow with a black outline around it. Here are its screen and cursor masks expressed as binary values. screen cursor cursor mask mask appearance 1001111111111111 0000000000000000 ** 1000111111111111 0010000000000000 *x* 1000011111111111 0011000000000000 *xx* 1000001111111111 0011100000000000 *xxx* 1000000111111111 0011110000000000 *xxxx* 1000000011111111 0011111000000000 *xxxxx* 1000000001111111 0011111100000000 *xxxxxx* 1000000000111111 0011111110000000 *xxxxxxx* 1000000000011111 0011111111000000 *xxxxxxxx* 1000000000001111 0011111000000000 *xxxxx***** 1000000011111111 0011011000000000 *xx*xx* 1000100001111111 0010001100000000 *x* *xx* 1001100001111111 0000001100000000 ** *xx* 1111110000111111 0000000110000000 *xx* 1111110000111111 0000000110000000 *xx* 1111111000111111 0000000000000000 *** The mouse driver first ANDs the screen mask with video memory at the mouse cursor position. This means the screen mask 1 bits leave video memory intact, while the 0 bits change the corresponding pixels to black. Next, the mouse driver XORs the result with the cursor mask. This time the cursor mask 0 bits leave video memory unchanged, while the 1 bits change the corresponding pixels to white. This produces a mouse cursor as shown above on the right, where a dot ( ) represents an unchanged pixel, an asterisk (*) a black pixel, and an x a white pixel. The following table summarizes the cursor appearance for all possible combinations of mask bits. 276 Fastgraph User's Guide screen mask bit cursor mask bit resulting cursor pixel 0 0 black 0 1 white 1 0 unchanged 1 1 inverted The color of an "inverted" pixel is n-k, where n is the maximum color number in the current video mode, and k is the color of the pixel being replaced. Also, "black" and "white" pixels are not necessarily these colors in 16-color and 256-color modes. More correctly, "black" pixels are displayed in the color assigned to palette 0, and "white" pixels are the displayed in the color assigned to palette 15 (255 in XVGA and SVGA 256-color modes). If you're using the CGA color modes, "black" pixels are displayed in the background color, and "white" pixels appear in color 3 (whose actual color is determined by the selected CGA palette). With an understanding of the way the default mouse cursor works in graphics modes, we're now ready to define our own mouse cursor. Shown below are the screen mask, cursor mask, and resulting appearance for a solid plus- shaped cursor. The hexadecimal equivalents of the binary mask values are also given. ----- screen mask ---- ----- cursor mask ---- cursor binary hex binary hex appearance 1110000000111111 E03F 0000000000000000 0000 ...*******...... 1110000000111111 E03F 0000111110000000 0F80 ...*xxxxx*...... 1110000000111111 E03F 0000111110000000 0F80 ...*xxxxx*...... 0000000000000111 0007 0000111110000000 0F80 ****xxxxx****... 0000000000000111 0007 0111111111110000 7FF0 *xxxxxxxxxxx*... 0000000000000111 0007 0111111111110000 7FF0 *xxxxxxxxxxx*... 0000000000000111 0007 0111111111110000 7FF0 *xxxxxxxxxxx*... 0000000000000111 0007 0111111111110000 7FF0 *xxxxxxxxxxx*... 0000000000000111 0007 0111111111110000 7FF0 *xxxxxxxxxxx*... 0000000000000111 0007 0000111110000000 0F80 ****xxxxx****... 1110000000111111 E03F 0000111110000000 0F80 ...*xxxxx*...... 1110000000111111 E03F 0000111110000000 0F80 ...*xxxxx*...... 1110000000111111 E03F 0000000000000000 0000 ...*******...... 1111111111111111 FFFF 0000000000000000 0000 ................ 1111111111111111 FFFF 0000000000000000 0000 ................ 1111111111111111 FFFF 0000000000000000 0000 ................ If we wanted to make the mouse cursor hollow rather than solid, the masks and resulting cursor appearance would look like this. ----- screen mask ---- ----- cursor mask ---- cursor binary hex binary hex appearance 1110000000111111 E03F 0000000000000000 0000 ...*******...... 1110111110111111 EFBF 0000000000000000 0000 ...*.....*...... 1110111110111111 EFBF 0000000000000000 0000 ...*.....*...... 0000111110000111 0F87 0000000000000000 0000 ****.....****... 0111111111110111 7FF7 0000000000000000 0000 *...........*... Chapter 14: Input Device Support 277 0111111111110111 7FF7 0000000000000000 0000 *...........*... 0111111111110111 7FF7 0000001000000000 0200 *.....x.....*... 0111111111110111 7FF7 0000000000000000 0000 *...........*... 0111111111110111 7FF7 0000000000000000 0000 *...........*... 0000111110000111 0F87 0000000000000000 0000 ****.....****... 1110111110111111 EFBF 0000000000000000 0000 ...*.....*...... 1110111110111111 EFBF 0000000000000000 0000 ...*.....*...... 1110000000111111 E03F 0000000000000000 0000 ...*******...... 1111111111111111 FFFF 0000000000000000 0000 ................ 1111111111111111 FFFF 0000000000000000 0000 ................ 1111111111111111 FFFF 0000000000000000 0000 ................ Note that the center bit defined in the cursor mask causes the corresponding pixel in video memory to be inverted. There is one more item needed to define a graphics mode mouse cursor completely. That item is the hot spot, or the actual screen position used or reported by the mouse driver. For the plus-shaped cursors just constructed, it would be sensible to define the hot spot in the center of the plus. The hot spot is specified relative to the upper left corner of the cursor, so its position within the cursor would be (6,6) -- that is, six pixels to the right and six pixels below the upper left corner. You can specify the hot spot offsets using negative values or values above 15 to position it outside the mouse cursor matrix if desired. The Fastgraph routine fg_mouseptr defines a mouse cursor in graphics modes. The first of its three arguments is a 32-element integer array, passed by reference. The array's first 16 elements contain the screen mask, and its second 16 elements contain the cursor mask. The remaining two arguments respectively specify the horizontal and vertical offsets for the hot spot. The fg_mouseptr routine has no effect in a text video mode. Example 14-10 is similar to example 14-9. It shows how to define a graphics mode mouse cursor using fg_mouseptr. The values stored in the solid and hollow arrays define the screen and cursor masks for the solid and hollow plus-shaped mouse cursors discussed earlier. After making the mouse cursor visible, the program uses the default mouse cursor until a key is pressed. Following this, it changes to the solid cursor. After another keystroke, the program changes to the hollow cursor. When you run example 14-10, compare the differences among the three mouse cursors. Example 14-10. #include <fastgraf.h> #include <stdio.h> #include <stdlib.h> void main(void); int solid[] = {0xE03F,0xE03F,0xE03F,0x0007,0x0007,0x0007,0x0007,0x0007, 0x0007,0x0007,0xE03F,0xE03F,0xE03F,0xFFFF,0xFFFF,0xFFFF, 0x0000,0x0F80,0x0F80,0x0F80,0x7FF0,0x7FF0,0x7FF0,0x7FF0, 0x7FF0,0x0F80,0x0F80,0x0F80,0x0000,0x0000,0x0000,0x0000}; int hollow[] = {0xE03F,0xEFBF,0xEFBF,0x0F87,0x7FF7,0x7FF7,0x7FF7,0x7FF7, 0x7FF7,0x0F87,0xEFBF,0xEFBF,0xE03F,0xFFFF,0xFFFF,0xFFFF, 0x0000,0x0000,0x0000,0x0000,0x0000,0x0000,0x0200,0x0000, 0x0000,0x0000,0x0000,0x0000,0x0000,0x0000,0x0000,0x0000}; 278 Fastgraph User's Guide void main() { int old_mode; int column, row, last_row; old_mode = fg_getmode(); fg_setmode(fg_automode()); if (fg_mouseini() < 0) { fg_setmode(old_mode); fg_reset(); exit(1); } fg_setcolor(15); fg_rect(0,fg_getmaxx(),0,fg_getmaxy()); fg_setcolor(12); column = fg_xalpha(fg_getmaxx()/2) - 6; last_row = fg_yalpha(fg_getmaxy()) + 1; for (row = 0; row < last_row; row++) { fg_locate(row,column); fg_text("example 14-10",13); } fg_mousevis(1); fg_waitkey(); fg_mouseptr(solid,6,6); fg_waitkey(); fg_mouseptr(hollow,6,6); fg_waitkey(); fg_setmode(old_mode); fg_reset(); } CGA Considerations The mouse driver treats the screen and cursor masks differently in the CGA four-color graphics modes (modes 4 and 5) than in the other graphics modes. In the CGA modes, each pair of mask bits corresponds to one pixel. This means the masks more closely resemble the mode-specific format used by fg_drwimage instead of the mode-independent format of fg_drawmap. Fastgraph uses a different default mouse cursor for modes 4 and 5. Its screen and cursor masks, as well as the resulting cursor appearance, are shown in the following diagram. screen cursor cursor mask mask appearance 0000111111111111 0000000000000000 ** 0000001111111111 0011000000000000 *** 0000000011111111 0011110000000000 **** Chapter 14: Input Device Support 279 0000000000111111 0011111100000000 ***** 0000000000001111 0011111111000000 ****** 0000000000000011 0011111111110000 ******* 0000000000000011 0011111100000000 ******* 0000000000111111 0011111110000000 ***** 0000000000001111 0011000011000000 ****** 0000110000001111 0000000011000000 ** *** 1111111100000011 0000000000110000 *** 1111111100000011 0010000000110000 *** 1111111111000011 0000000000000000 ** 1111111111111111 0000000000000000 1111111111111111 0000000000000000 1111111111111111 0000000000000000 As you can see, the resulting mouse cursor is eight pixels wide instead of 16. Another important point concerning mouse cursors in modes 4 and 5 is the chance of pixel bleeding, or the changing of colors within the mouse cursor as it moves horizontally. Bleeding will occur if you use the bit pairs 01 or 10 in either mask to represent a pixel. In the default masks for modes 4 and 5, note that only the binary values 00 and 11 appear as bit pairs. Keep this in mind if you create your own masks in these video modes. Joystick Support The third type of input device supported by Fastgraph is the joystick. Although joysticks are not as popular as mice, they are often preferable when a user's reactions are critical, such as in an arcade-style game. Fastgraph includes routines for initializing a joystick, reading a joystick's position or button status, and making a joystick behave analogously to the keyboard. These routines are independent of the rest of Fastgraph and thus do not require that you first call the fg_setmode routine. Joysticks are connected to a system through a game port. The PCjr and Tandy 1000 systems come equipped with two game ports, and hence support two joysticks. On other systems in the IBM family, you can install a game port card that contains either one or two game ports. If the card only has one game port, you can use a splitter cable to fork two joysticks into the port. Initializing Joysticks Before you can use any of Fastgraph's joystick support routines with a specific joystick, you must initialize that joystick. The fg_initjoy routine performs this task. This routine requires a single integer argument that specifies which joystick to initialize, either 1 or 2. If successful, fg_initjoy returns 0 as the function value. If the machine has no game port, or if the requested joystick is not connected to the game port, fg_initjoy returns -1. When you use fg_initjoy, the joystick being initialized must be centered (that is, the stick itself must not be tilted in either direction). Example 14-11 uses the fg_initjoy routine to try to initialize both joysticks. For each joystick, the program prints a message stating whether or not the initialization was successful. 280 Fastgraph User's Guide Example 14-11. #include <fastgraf.h> #include <stdio.h> void main(void); void main() { if (fg_initjoy(1) < 0) printf("Joystick 1 not available.\n"); else printf("Joystick 1 found.\n"); if (fg_initjoy(2) < 0) printf("Joystick 2 not available.\n"); else printf("Joystick 2 found.\n"); } Reporting Joystick Status Each joystick can report three items: its horizontal position, its vertical position, and the button status. Fastgraph includes routines for obtaining each of these quantities. The fg_getxjoy and fg_getyjoy routines respectively return the horizontal and vertical position of the indicated joystick. Both routines require a single integer argument, whose value is either 1 or 2, to identify the joystick. The requested position is returned as the function value. Horizontal coordinates increase as the joystick moves to the right, while vertical coordinates increase as the joystick moves downward. If fg_initjoy did not initialize the specified joystick, or if your program hasn't yet called fg_initjoy, both fg_getxjoy and fg_getyjoy will return the value -1. Joystick characteristics vary more than those of any other input device. The values returned by fg_getxjoy and fg_getyjoy depend on the system's processor speed and the brand of joystick used. It often suffices to know the joystick position relative to its previous position, in which case the actual coordinate values do not matter. However, if you must rely on specific coordinate values, your program must perform some type of manual joystick calibration and then scale the coordinates reported by fg_getxjoy and fg_getyjoy as needed. The other piece of information joysticks provide is the button status. Most joysticks have two buttons, called the top and bottom buttons. Others have three buttons, but one of them duplicates the functionality of another (for example, a joystick might have one bottom button on its left side and another on its right side). The Fastgraph routine fg_button returns the joystick button status as its function value. Like fg_getxjoy and fg_getyjoy, the fg_button routine requires a single argument that specifies the joystick number. The meaning of the returned value is shown below. Chapter 14: Input Device Support 281 value meaning 0 neither button pressed 1 top button pressed 2 bottom button pressed 3 top and bottom buttons pressed You don't need to call fg_initjoy before using fg_button. If the specified joystick is not present, the fg_button routine will return zero. Example 14-12 uses fg_getxjoy, fg_getyjoy, and fg_button to poll both joysticks at half-second intervals. It then displays the joystick number (1 or 2), horizontal position, vertical position, and button status for each joystick. As the program runs, you can move the joysticks and watch how the movements affect the displayed coordinate values. The program continues doing this until you press Ctrl/C or Ctrl/Break to stop it. Example 14-12. #include <fastgraf.h> #include <stdio.h> void main(void); void main() { int b, x, y; fg_initjoy(1); fg_initjoy(2); while (1) { x = fg_getxjoy(1); y = fg_getyjoy(1); b = fg_button(1); printf("1: %3d %3d %1d\n",x,y,b); x = fg_getxjoy(2); y = fg_getyjoy(2); b = fg_button(2); printf("2: %3d %3d %1d\n\n",x,y,b); fg_waitfor(9); } } There are two ways of effectively monitoring joystick button status. One is to call fg_button at many places in your program and then take the necessary action depending on the button status. However, the preferable method is to extend the BIOS time-of-day interrupt to check the button status at each clock tick (there are 18.2 clock ticks per second), set a flag if a button is pressed, and then check the flag as needed in your program. Information on changing the BIOS time-of-day interrupt appears in Appendix C of this document. Keyboard Emulation Although we can use the fg_getxjoy and fg_getyjoy routines to monitor relative joystick movements, it is usually easier to do this with another Fastgraph routine, fg_intjoy. This routine is similar to the fg_intkey 282 Fastgraph User's Guide routine in that it returns two values that are equivalent to the standard or extended keyboard codes for analogous keystrokes. The fg_intjoy routine needs three arguments. The first argument specifies the joystick number, either 1 or 2. The second and third arguments, both one-byte quantities passed by reference, receive the standard and extended keyboard codes analogous to the joystick movement and button status. The second argument receives a value of 13 (the standard keyboard code for the Enter key) if any joystick button is pressed; it receives a value of 0 if not. The third argument receives a value corresponding to the extended keyboard code for one of the directional keys on the numeric keypad, as summarized in the following table. joystick position corresponding key extended key code up and left Home 71 up up arrow 72 up and right PgUp 73 left left arrow 75 centered (no action) 0 right right arrow 77 down and left End 79 down down arrow 80 down and right PgDn 81 The fg_intjoy routine will set both key code arguments to zero if the specified joystick has not yet been initialized. Example 14-13 is similar to example 14-11, but it uses fg_intjoy in place of fg_getxjoy and fg_getyjoy to report relative joystick position. This program does not report the joystick button status as example 14-11 does, but you could readily add this feature to it. Example 14-13. #include <fastgraf.h> #include <stdio.h> void main(void); void main() { char key, aux; fg_initjoy(1); fg_initjoy(2); while (1) { fg_intjoy(1,&key,&aux); printf("1: %2d %2d\n",key,aux); fg_intjoy(2,&key,&aux); printf("2: %2d %2d\n\n",key,aux); fg_waitfor(9); } } Chapter 14: Input Device Support 283 Special Joystick Considerations If you develop a program that supports only one joystick, you should use joystick 1. The reasons for this are twofold. First, it will make your program consistent with most other products that support joysticks. Second, and perhaps more importantly, many Tandy 1000 series machines cannot determine if joystick 2 is present when neither joystick is connected. This means if you use joystick 2 instead of joystick 1 in a single joystick program, you won't be able to tell if a joystick is available when running on a Tandy 1000. Summary of Input Routines This section summarizes the functional descriptions of the Fastgraph routines presented in this chapter. More detailed information about these routines, including their arguments and return values, may be found in the Fastgraph Reference Manual. FG_BUTTON returns information about the state of either joystick's buttons. FG_CAPSLOCK determines the state of the CapsLock key. FG_GETKEY waits for a keystroke (or reads the next entry from the BIOS keyboard buffer). It returns the keystroke's standard or extended keyboard code. FG_GETXJOY and FG_GETYJOY return the horizontal and vertical coordinate position of the specified joystick. The actual coordinates depend on the processor speed and brand of joystick used. FG_INITJOY initializes joystick 1 or 2 and must be called before using fg_getxjoy, fg_getyjoy, or fg_intjoy. It returns a status code indicating whether or not the initialization was successful. FG_INTJOY returns the standard and extended keyboard codes analogous to the current position and button status of the specified joystick. FG_INTKEY reads the next entry from the BIOS keyboard buffer and returns the keystroke's standard or extended keyboard code. It is similar to fg_getkey, but it does not wait for a keystroke if the keyboard buffer is empty. FG_KBINIT enables or disables the Fastgraph low-level keyboard handler. If the keyboard handler is already in the requested state, nothing happens. FG_KBTEST determines if the key having the specified scan code is now pressed or released. The low-level keyboard handler must be enabled for this routine to work properly. FG_MOUSEBUT returns information about mouse button press or release counts, as well as the mouse cursor position at the time of the last button press or release. 284 Fastgraph User's Guide FG_MOUSECUR defines the appearance of the mouse cursor in text video modes. FG_MOUSEFIN unhooks Fastgraph's XVGA or SVGA mouse handler from the mouse driver. This routine should be used just before reverting to text mode in programs that have called fg_mouseini in XVGA or SVGA graphics modes. It has no effect in other video modes. FG_MOUSEINI initializes the mouse and must be called before any of Fastgraph's other mouse support routines. It returns an error status if the mouse driver has not been loaded, or if the mouse is not connected. FG_MOUSELIM defines the rectangular area in which the mouse cursor may move. FG_MOUSEMOV moves the mouse cursor to the specified character cell (in text modes) or screen space position (in graphics modes). FG_MOUSEPOS returns the current mouse position and button status. FG_MOUSEPTR defines the shape and appearance of the mouse cursor in graphics video modes. FG_MOUSESPD defines the number of mickey units per eight pixels of cursor movement. This effectively controls the speed at which the mouse cursor moves relative to the movement of the mouse itself. FG_MOUSEVIS makes the mouse cursor visible or invisible. FG_NUMLOCK determines the state of the NumLock key. FG_SCRLOCK determines the state of the ScrollLock key (which is not present on some keyboards). FG_SETCAPS controls the state of the CapsLock key. FG_SETNUM controls the state of the NumLock key. FG_WAITKEY flushes the BIOS keyboard buffer (that is, removes any type- ahead characters) and then waits for another keystroke.