translate_keyboard_state

Translates the contents of a EventKey into a keyval, effective group, and level.

Modifiers that affected the translation and are thus unavailable for application use are returned in consumed_modifiers. See Groups for an explanation of groups and levels. The effective_group is the group that was actually used for the translation; some keys such as Enter are not affected by the active keyboard group. The level is derived from state. For convenience, EventKey already contains the translated keyval, so this function isn’t as useful as you might think.

consumed_modifiers gives modifiers that should be masked outfrom state when comparing this key press to a hot key. For instance, on a US keyboard, the `plus` symbol is shifted, so when comparing a key press to a `<Control>plus` accelerator `<Shift >` should be masked out.

// We want to ignore irrelevant modifiers like ScrollLock
#define ALL_ACCELS_MASK (GDK_CONTROL_MASK | GDK_SHIFT_MASK | GDK_MOD1_MASK)
gdk_keymap_translate_keyboard_state (keymap, event->hardware_keycode,
                                     event->state, event->group,
                                     &keyval, NULL, NULL, &consumed);
if (keyval == GDK_PLUS &&
    (event->state & ~consumed & ALL_ACCELS_MASK) == GDK_CONTROL_MASK)
  // Control was pressed

An older interpretation consumed_modifiers was that it contained all modifiers that might affect the translation of the key; this allowed accelerators to be stored with irrelevant consumed modifiers, by doing:

// XXX Don’t do this XXX
if (keyval == accel_keyval &&
    (event->state & ~consumed & ALL_ACCELS_MASK) == (accel_mods & ~consumed))
  // Accelerator was pressed

However, this did not work if multi-modifier combinations were used in the keymap, since, for instance, `<Control>` would be masked out even if only `<Control><Alt>` was used in the keymap. To support this usage as well as well as possible, all single modifier combinations that could affect the key for any combination of modifiers will be returned in consumed_modifiers; multi-modifier combinations are returned only when actually found in state. When you store accelerators, you should always store them with consumed modifiers removed. Store `<Control>plus`, not `<Control><Shift>plus`,

Parameters:

this	a Keymap
hardware_keycode	a keycode
state	a modifier state
group	active keyboard group
keyval	return location for keyval, or null
effective_group	return location for effective group, or null
level	return location for level, or null
consumed_modifiers	return location for modifiers that were used to determine the group or level, or null

Returns:

true if there was a keyval bound to the keycode/state/group