Description
Key values are the codes which are sent whenever a key is pressed or released.
They appear in the keyval field of the
GdkEventKey structure, which is passed to signal handlers for the
"key-press-event" and "key-release-event" signals.
The complete list of key values can be found in the <gdk/gdkkeysyms.h>
header file. <gdk/gdkkeysyms.h> is not included in <gtk/gtk.h>,
it must be included independently, because the file is quite large.
Key values can be converted into a string representation using
gdk_keyval_name(). The reverse function, converting a string to a key value,
is provided by gdk_keyval_from_name().
The case of key values can be determined using gdk_keyval_is_upper() and
gdk_keyval_is_lower(). Key values can be converted to upper or lower case
using gdk_keyval_to_upper() and gdk_keyval_to_lower().
When it makes sense, key values can be converted to and from
Unicode characters with gdk_keyval_to_unicode() and gdk_unicode_to_keyval().
One GdkKeymap object exists for each user display. GTK 2 supports only one
display, so gdk_keymap_get_default() returns the singleton GdkKeymap. A keymap
is a mapping from GdkKeymapKey to key values. You can think of a GdkKeymapKey
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
GdkKeymapKey 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 gdk_keymap_translate_keyboard_state() 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 gdk_keymap_translate_keyboard_state() 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. GdkEventKey already
contains this keyval, however, so you don't normally need to call
gdk_keymap_translate_keyboard_state() just to get the keyval.
Details
struct GdkKeymap
struct GdkKeymap
{
GObject parent_instance;
}; |
A GdkKeymap defines the translation from keyboard state
(including a hardware key, a modifier mask, and active keyboard group)
to a keyval. This translation has two phases. The first phase is
to determine the effective keyboard group and level for the keyboard
state; the second phase is to look up the keycode/group/level triplet
in the keymap and see what keyval it corresponds to.
struct GdkKeymapKey
struct GdkKeymapKey
{
guint keycode;
gint group;
gint level;
}; |
A GdkKeymapKey is a hardware key that can
be mapped to a keyval.
gdk_keymap_get_default ()
Gets the GdkKeymap for the default display.
gdk_keymap_lookup_key ()
Looks up the keyval mapped to a keycode/group/level triplet.
If no keyval is bound to key, returns 0. For normal user input,
you want to use gdk_keymap_translate_keyboard_state() instead of
this function, since the effective group/level may not be
the same as the current keyboard state.
gdk_keymap_translate_keyboard_state ()
gboolean gdk_keymap_translate_keyboard_state
(GdkKeymap *keymap,
guint hardware_keycode,
GdkModifierType state,
gint group,
guint *keyval,
gint *effective_group,
gint *level,
GdkModifierType *consumed_modifiers); |
Translates the contents of a GdkEventKey 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 gdk_keyval_get_keys() 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, GdkEventKey already contains the translated
keyval, so this function isn't as useful as you might think.
gdk_keymap_get_entries_for_keyval ()
gboolean gdk_keymap_get_entries_for_keyval
(GdkKeymap *keymap,
guint keyval,
GdkKeymapKey **keys,
gint *n_keys); |
Obtains a list of keycode/group/level combinations that will
generate keyval. Groups and levels are two kinds of keyboard mode;
in general, the level determines whether the top or bottom symbol
on a key is used, and the group determines whether the left or
right symbol is used. On US keyboards, the shift key changes the
keyboard level, and there are no groups. A group switch key might
convert a keyboard between Hebrew to English modes, for example.
GdkEventKey contains a group field that indicates the active
keyboard group. The level is computed from the modifier mask.
The returned array should be freed
with g_free().
gdk_keymap_get_entries_for_keycode ()
gboolean gdk_keymap_get_entries_for_keycode
(GdkKeymap *keymap,
guint hardware_keycode,
GdkKeymapKey **keys,
guint **keyvals,
gint *n_entries); |
Returns the keyvals bound to hardware_keycode.
The Nth GdkKeymapKey in keys is bound to the Nth
keyval in keyvals. Free the returned arrays with g_free().
When a keycode is pressed by the user, the keyval from
this list of entries is selected by considering the effective
keyboard group and level. See gdk_keymap_translate_keyboard_state().
gdk_keymap_get_direction ()
PangoDirection gdk_keymap_get_direction (GdkKeymap *keymap); |
Returns the direction of the keymap.
gdk_keyval_name ()
gchar* gdk_keyval_name (guint keyval); |
Converts a key value into a symbolic name.
The names are the same as those in the <gdk/gdkkeysyms.h> header file
but without the leading "GDK_".
gdk_keyval_from_name ()
guint gdk_keyval_from_name (const gchar *keyval_name); |
Converts a key name to a key value.
gdk_keyval_convert_case ()
void gdk_keyval_convert_case (guint symbol,
guint *lower,
guint *upper); |
Obtains the upper- and lower-case versions of the keyval symbol.
Examples of keyvals are GDK_a, GDK_Enter, GDK_F1, etc.
gdk_keyval_to_upper ()
guint gdk_keyval_to_upper (guint keyval); |
Converts a key value to upper case, if applicable.
gdk_keyval_to_lower ()
guint gdk_keyval_to_lower (guint keyval); |
Converts a key value to lower case, if applicable.
gdk_keyval_is_upper ()
gboolean gdk_keyval_is_upper (guint keyval); |
Returns TRUE if the given key value is in upper case.
gdk_keyval_is_lower ()
gboolean gdk_keyval_is_lower (guint keyval); |
Returns TRUE if the given key value is in lower case.
gdk_keyval_to_unicode ()
guint32 gdk_keyval_to_unicode (guint keyval); |
Convert from a GDK key symbol to the corresponding ISO10646 (Unicode)
character.
gdk_unicode_to_keyval ()
guint gdk_unicode_to_keyval (guint32 wc); |
Convert from a ISO10646 character to a key symbol.