1keyboard_lowlevel_callback(3)   Allegro manual   keyboard_lowlevel_callback(3)
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NAME

6       keyboard_lowlevel_callback  -  User  specified low level keyboard event
7       handler. Allegro game programming library.
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SYNOPSIS

10       #include <allegro.h>
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13       extern void (*keyboard_lowlevel_callback)(int scancode);
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DESCRIPTION

16       If set, this function is called by the keyboard handler in response  to
17       every keyboard event, both presses (including keyboard repeat rate) and
18       releases. It will be passed a raw keyboard scancode byte (scancodes are
19       7  bits  long),  with  the  top bit (8th bit) clear if the key has been
20       pressed or set if it was released. This routine executes in  an  inter‐
21       rupt context, so it must be in locked memory. Example:
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23          volatile int key_down, key_up;
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25          void keypress_watcher(int scancode)
26          {
27             if (scancode & 0x80) {
28                key_up = 1;
29             } else {
30                key_down = 1;
31             }
32          } END_OF_FUNCTION(keypress_watcher)
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34          ...
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36             install_timer();
37             LOCK_FUNCTION(silence_g_key);
38             LOCK_VARIABLE(key_down);
39             LOCK_VARIABLE(key_up);
40             install_keyboard();
41             keyboard_lowlevel_callback = keypress_watcher;
42             /* Disable keyboard repeat to get typewriter effect. */
43             set_keyboard_rate(0, 0);
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45          ...
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47             while (game_loop) {
48                if (key_down) {
49                   key_down = 0;
50                   /* Play sample of typewriter key press. */
51                }
52                if (key_up) {
53                   key_up = 0;
54                   /* Play sample of typewriter key release. */
55                }
56             }
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SEE ALSO

60       install_keyboard(3),    keyboard_callback(3),    keyboard_ucallback(3),
61       exkeys(3)
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65Allegro                          version 4.2.2   keyboard_lowlevel_callback(3)
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