Functions for manipulating keyboard codes

Key values are the codes which are sent whenever a key is pressed or released. They appear in the keyval field of the EventKey structure, which is passed to signal handlers for the keyPressEvent and keyReleaseEvent signals.

Key values are regularly updated from the upstream X.org X11 implementation, so new values are added regularly. They will be prefixed with GDK_ rather than XF86XK_ or ' (for older symbols)'.

Key values can be converted into a string representation using keyvalName. The reverse function, converting a string to a key value, is provided by keyvalFromName.

The case of key values can be determined using keyvalIsUpper. Key values can be converted to upper or lower case using keyvalToUpper and keyvalToLower.

When it makes sense, key values can be converted to and from Unicode characters with keyvalToUnicode.

One Keymap object exists for each user display. keymapGetDefault returns the Keymap for the default display; to obtain keymaps for other displays, use keymapGetForDisplay. A keymap is a mapping from KeymapKey to key values. You can think of a KeymapKey as a representation of a symbol printed on a physical keyboard key. That is, it contains three pieces of information. First, it contains the hardware keycode; this is an identifying number for a physical key. Second, it contains the level of the key. The level indicates which symbol on the key will be used, in a vertical direction. So on a standard US keyboard, the key with the number "1" on it also has the exclamation point "!" character on it. The level indicates whether to use the "1" or the "!" symbol. The letter keys are considered to have a lowercase letter at level 0, and an uppercase letter at level 1, though only the uppercase letter is printed. Third, the KeymapKey contains a group; groups are not used on standard US keyboards, but are used in many other countries. On a keyboard with groups, there can be 3 or 4 symbols printed on a single key. The group indicates movement in a horizontal direction. Usually groups are used for two different languages. In group 0, a key might have two English characters, and in group 1 it might have two Hebrew characters. The Hebrew characters will be printed on the key next to the English characters.

In order to use a keymap to interpret a key event, it's necessary to first convert the keyboard state into an effective group and level. This is done via a set of rules that varies widely according to type of keyboard and user configuration. The function keymapTranslateKeyboardState accepts a keyboard state -- consisting of hardware keycode pressed, active modifiers, and active group -- applies the appropriate rules, and returns the group/level to be used to index the keymap, along with the modifiers which did not affect the group and level. i.e. it returns unconsumed modifiers. The keyboard group may differ from the effective group used for keymap lookups because some keys don't have multiple groups - e.g. the Enter key is always in group 0 regardless of keyboard state.

Note that keymapTranslateKeyboardState also returns the keyval, i.e. it goes ahead and performs the keymap lookup in addition to telling you which effective group/level values were used for the lookup. EventKey already contains this keyval, however, so you don't normally need to call keymapTranslateKeyboardState just to get the keyval.

 | GObject
 | +----Keymap