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Chapter 14
Input Device Support
302 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
Chapter 14: Input Device Support 303
Ctrl+Q 17 1 49 Q 81 q 113
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
304 Fastgraph User's Guide
Tab Ctrl+I 9
Enter Ctrl+M 13
Escape Ctrl+[ 27
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 fg_intkey detects an empty keyboard buffer, it sets both
arguments to zero.
Example 14-1 is a simple program that uses fg_getkey. 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_initpm and fg_getkey are
the only Fastgraph routines 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;
fg_initpm();
Chapter 14: Input Device Support 305
do {
fg_getkey(&key,&aux);
printf("key = %3d aux = %3d\n",key,aux);
}
while (key != ESC);
}
Example 14-2 reads keystrokes using fg_intkey at half-second intervals
(18.2 fg_waitfor units equal 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;
fg_initpm();
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
306 Fastgraph User's Guide
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 fg_capslock, fg_numlock, and
fg_scrlock to print messages describing the current state of these three keys.
Example 14-3.
#include <fastgraf.h>
#include <stdio.h>
void main(void);
void main()
{
fg_initpm();
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_initpm();
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
Chapter 14: Input Device Support 307
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
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 fg_kbtest 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 scan codes. If the corresponding key is
pressed, fg_kbtest returns 1. If it is released, the routine returns zero. The
fg_kbtest routine can test if any key is pressed if you pass it the value 0
instead of a specific scan code. The following table lists the scan codes
corresponding to 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
308 Fastgraph User's Guide
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-
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 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_initpm();
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");
}
Chapter 14: Input Device Support 309
Fastgraph includes two other routines for the low-level keyboard handler.
The fg_kblast function returns the scan code for the most recent keypress
processed by the low-level keyboard handler. If there have been no key presses
since calling fg_kbinit, the return value will be zero. The fg_kbreset routine
resets the state of Fastgraph's low-level keyboard handler to what it was
after being initialized with fg_kbinit(1). This has the effect of "flushing"
the keyboard handler. Neither of these two functions has any arguments.
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
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 Fastgraph's fg_mouseini
function to initialize the mouse within the program.
The fg_mouseini function 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). The return value will also be -1 if fg_mouseini is called when
a virtual buffer is active. 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
310 Fastgraph User's Guide
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()
{
int status;
fg_initpm();
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 cannot 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.
____________________
(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.
Chapter 14: Input Device Support 311
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 shown here:
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.
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 fg_mousevis.
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 already in the requested
state, fg_mousevis does nothing.
If the mouse cursor is in an area of the screen being updated, or if it
moves into this area during the update process, you must make the mouse cursor
invisible or freeze it at its current position. You must also do this when
performing any video output in the native EGA and VGA graphics modes (modes 13
through 18). Instead of checking for these conditions, it is often 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. An
alternative to making the mouse cursor invisible is freezing it at its current
position using fg_mousepos and fg_mouselim (these routines will be described
shortly) during screen updates and then restoring the default mouse limits.
Note, however, that this method only works if the mouse cursor is outside the
area being updated. You must also make the mouse cursor invisible when
changing 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
312 Fastgraph User's Guide
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, though for some mouse drivers it is 1/400 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 fg_mousevis,
fg_mousemov, fg_mouselim, and fg_mousespd. 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 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);
Chapter 14: Input Device Support 313
void main()
{
int maxx, maxy;
int old_mode;
fg_initpm();
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);
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 shown here:
314 Fastgraph User's Guide
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 absolute value of first argument specifies
the button of interest (1 means the left button, 2 is the right button, and 3
is the middle button), while its actual value determines if we're checking
presses or releases. If the 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
fg_mousepos and fg_mousebut. The program first establishes the video mode and
then initializes the mouse (the program exits if the 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()
Chapter 14: Input Device Support 315
{
int old_mode;
int buttons, count;
int x, y;
char string[25];
fg_initpm();
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);
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.
316 Fastgraph User's Guide
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)
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
Chapter 14: Input Device Support 317
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;
fg_initpm();
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);
}
fg_mousevis(1);
fg_waitkey();
fg_mousecur(0x7FFF,0x7F00);
fg_waitkey();
fg_setmode(old_mode);
fg_reset();
}
318 Fastgraph User's Guide
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 text modes. In fact, it closely resembles the
mode-independent bitmap format used by fg_drawmap. 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.
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
Chapter 14: Input Device Support 319
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 here 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 *...........*...
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 ................
320 Fastgraph User's Guide
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 make sense 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 16-bit 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. In C or C++
programs, we recommend using the short data type for the mask array because
short means a 16-bit integer for both 16-bit and 32-bit environments.
Similarly, FORTRAN programmers should define the mask array as an INTEGER*2
item.
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 between the three mouse cursors.
Example 14-10.
#include <fastgraf.h>
#include <stdio.h>
#include <stdlib.h>
void main(void);
short 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};
short hollow[] = {0xE03F,0xEFBF,0xEFBF,0x0F87,
0x7FF7,0x7FF7,0x7FF7,0x7FF7,
0x7FF7,0x0F87,0xEFBF,0xEFBF,
0xE03F,0xFFFF,0xFFFF,0xFFFF,
0x0000,0x0000,0x0000,0x0000,
Chapter 14: Input Device Support 321
0x0000,0x0000,0x0200,0x0000,
0x0000,0x0000,0x0000,0x0000,
0x0000,0x0000,0x0000,0x0000};
void main()
{
int old_mode;
int column, row, last_row;
fg_initpm();
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.
322 Fastgraph User's Guide
screen cursor cursor
mask mask appearance
0000111111111111 0000000000000000 **
0000001111111111 0011000000000000 ***
0000000011111111 0011110000000000 ****
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.
XVGA and SVGA Considerations
In XVGA graphics modes and 256-color SVGA graphics modes (20 to 27), it's
possible to create a multicolored mouse cursor. To do this, use fg_mouse256
instead of fg_mouseptr to define the mouse cursor's shape and appearance. The
fg_mouse256 routine uses the same arguments as fg_mouseptr, but the masks are
passed in a 512-byte array consisting of a 256-byte screen mask followed by a
256-byte cursor mask. As with fg_mouseptr, each mask is structured as a 16x16
pixel grid, but each pixel is represented by a byte value rather than a single
bit.
The mouse driver displays the mouse cursor by logically ANDing video
memory with the screen mask, and then XORing that result with the cursor mask.
This normally means the screen mask values are either 0 or 255, while cursor
mask values are between 0 and 255. For example, consider again the default
graphics mode mouse cursor (the arrow). If we wanted to display the cursor in
yellow (color 14) instead of its default white, you would expand the screen
mask from 16 to 256 bytes, replacing the zero bits in the "standard" mask with
zero bytes and replacing the one bits with the value 255. You would similarly
expand the cursor mask, replacing the zero bits with zero bytes and the one
bits with the value 14.
Chapter 14: Input Device Support 323
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 fg_setmode.
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 card
with 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.
Example 14-11.
#include <fastgraf.h>
#include <stdio.h>
void main(void);
void main()
{
fg_initpm();
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");
}
324 Fastgraph User's Guide
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 -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,
fg_button requires a single argument that specifies the joystick number. The
meaning of the return value is shown here:
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, fg_button will return a value of 0.
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);
Chapter 14: Input Device Support 325
void main()
{
int b, x, y;
fg_initpm();
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.
Keyboard Emulation
Although we can use fg_getxjoy and fg_getyjoy to monitor relative
joystick movements, it is usually easier to do this with another Fastgraph
routine, fg_intjoy. This routine is similar to fg_intkey in that it returns
two values 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
326 Fastgraph User's Guide
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_initpm();
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);
}
}
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, 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.
Chapter 14: Input Device Support 327
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 Fastgraph's low-level keyboard handler. If
the keyboard handler is already in the requested state, nothing happens.
FG_KBLAST returns the scan code for the most recent keypress processed by
Fastgraph's low-level keyboard handler.
FG_KBRESET resets the state of Fastgraph's low-level keyboard handler to
what it was after being enabled with fg_kbinit.
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_MOUSE256 defines the shape and appearance of a multicolored mouse
cursor in XVGA and 256-color SVGA graphics modes.
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.
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
328 Fastgraph User's Guide
mouse driver has not been loaded, if the mouse is not connected, or if a
virtual buffer is active.
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.