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doc: add note about X11 vs. extended keycodes 

Signed-off-by: Ran Benita <ran234@gmail.com>
master
Ran Benita 2012-10-22 17:53:44 +02:00
parent 0779d9dcad
commit 3a5f87b8e9
1 changed files with 20 additions and 0 deletions
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xkbcommon/xkbcommon.h
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@ -147,7 +147,17 @@ struct xkb_state;
* keymap would assign each of them a keycode, by which the user should
* refer to the key throughout the library.
*
* Historically, the X11 protocol, and consequentially the XKB protocol,
* assign only 8 bits for keycodes. This limits the number of different
* keys that can be used simultaneously in a single keymap to 256
* (disregarding other limitations). This library does not share this limit;
* keycodes beyond 255 ('extended keycodes') are not treated specially.
* Keymaps and applications which are compatible with X11 should not use
* these keycodes.
*
* @todo Explain how keycodes are mapped to scancodes.
*
* @sa xkb_keycode_is_legal_ext() xkb_keycode_is_legal_x11()
*/
typedef uint32_t xkb_keycode_t;
@ -260,7 +270,17 @@ typedef uint32_t xkb_led_mask_t;
#define XKB_LED_INVALID (0xffffffff)
#define XKB_KEYCODE_MAX (0xffffffff - 1)
/**
* Test whether a value is a valid extended keycode.
* @sa xkb_keycode_t
**/
#define xkb_keycode_is_legal_ext(key) (key <= XKB_KEYCODE_MAX)
/**
* Test whether a value is a valid X11 keycode.
* @sa xkb_keycode_t
*/
#define xkb_keycode_is_legal_x11(key) (key >= 8 && key <= 255)
/**