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Key Values

Key Values — Functions for manipulating keyboard codes

Synopsis


#include <gdk/gdk.h>


            GdkKeymap;
            GdkKeymapKey;
GdkKeymap*  gdk_keymap_get_default          (void);
GdkKeymap*  gdk_keymap_get_for_display      (GdkDisplay *display);
guint       gdk_keymap_lookup_key           (GdkKeymap *keymap,
                                             const GdkKeymapKey *key);
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);
gboolean    gdk_keymap_get_entries_for_keyval
                                            (GdkKeymap *keymap,
                                             guint keyval,
                                             GdkKeymapKey **keys,
                                             gint *n_keys);
gboolean    gdk_keymap_get_entries_for_keycode
                                            (GdkKeymap *keymap,
                                             guint hardware_keycode,
                                             GdkKeymapKey **keys,
                                             guint **keyvals,
                                             gint *n_entries);
PangoDirection gdk_keymap_get_direction     (GdkKeymap *keymap);

gchar*      gdk_keyval_name                 (guint keyval);
guint       gdk_keyval_from_name            (const gchar *keyval_name);

void        gdk_keyval_convert_case         (guint symbol,
                                             guint *lower,
                                             guint *upper);
guint       gdk_keyval_to_upper             (guint keyval);
guint       gdk_keyval_to_lower             (guint keyval);
gboolean    gdk_keyval_is_upper             (guint keyval);
gboolean    gdk_keyval_is_lower             (guint keyval);

guint32     gdk_keyval_to_unicode           (guint keyval);
guint       gdk_unicode_to_keyval           (guint32 wc);


Object Hierarchy


  GObject
   +----GdkKeymap

Signal Prototypes


"direction-changed"
            void        user_function      (GdkKeymap *keymap,
                                            gpointer user_data);
"keys-changed"
            void        user_function      (GdkKeymap *keymap,
                                            gpointer user_data);

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. gdk_keymap_get_default() returns the GdkKeymap for the default display; to obtain keymaps for other displays, use gdk_keymap_get_for_display(). 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

GdkKeymap

typedef struct _GdkKeymap GdkKeymap;

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.


GdkKeymapKey

typedef struct {
  guint keycode;
  gint  group;
  gint  level;
} GdkKeymapKey;

A GdkKeymapKey is a hardware key that can be mapped to a keyval.

guint keycode;the hardware keycode. This is an identifying number for a physical key.
gint 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.
gint 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.

gdk_keymap_get_default ()

GdkKeymap*  gdk_keymap_get_default          (void);

Returns the GdkKeymap attached to the default display.

Returns : the GdkKeymap attached to the default display.

gdk_keymap_get_for_display ()

GdkKeymap*  gdk_keymap_get_for_display      (GdkDisplay *display);

Returns the GdkKeymap attached to display.

display : the GdkDisplay.
Returns : the GdkKeymap attached to display.

Since 2.2


gdk_keymap_lookup_key ()

guint       gdk_keymap_lookup_key           (GdkKeymap *keymap,
                                             const GdkKeymapKey *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.

keymap : a GdkKeymap or NULL to use the default keymap
key : a GdkKeymapKey with keycode, group, and level initialized
Returns : a keyval, or 0 if none was mapped to the given key

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.

Note

consumed_modifiers gives modifiers that should be masked out from 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,

keymap : a GdkKeymap, or NULL to use the default
hardware_keycode : a keycode
state : a modifier state
group : active keyboard group
keyval : return location for keyval
effective_group : return location for effective group
level : return location for level
consumed_modifiers : return location for modifiers that were used to determine the group or level
Returns : TRUE if there was a keyval bound to the keycode/state/group

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().

keymap : a GdkKeymap, or NULL to use the default keymap
keyval : a keyval, such as GDK_a, GDK_Up, GDK_Return, etc.
keys : return location for an array of GdkKeymapKey
n_keys : return location for number of elements in returned array
Returns : TRUE if keys were found and returned

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().

keymap : a GdkKeymap or NULL to use the default keymap
hardware_keycode : a keycode
keys : return location for array of GdkKeymapKey, or NULL
keyvals : return location for array of keyvals, or NULL
n_entries : length of keys and keyvals
Returns : TRUE if there were any entries

gdk_keymap_get_direction ()

PangoDirection gdk_keymap_get_direction     (GdkKeymap *keymap);

Returns the direction of the keymap.

keymap :a GdkKeymap or NULL to use the default keymap. Returns: PANGO_DIRECTION_LTR or PANGO_DIRECTION_RTL.
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_".

keyval :a key value.
Returns :a string containing the name of the key, or NULL if keyval is not a valid key. The string should not be modified.

gdk_keyval_from_name ()

guint       gdk_keyval_from_name            (const gchar *keyval_name);

Converts a key name to a key value.

keyval_name :a key name.
Returns :the corresponding key value, or GDK_VoidSymbol if the key name is not a valid key.

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.

symbol : a keyval
lower : return location for lowercase version of symbol
upper : return location for uppercase version of symbol

gdk_keyval_to_upper ()

guint       gdk_keyval_to_upper             (guint keyval);

Converts a key value to upper case, if applicable.

keyval :a key value.
Returns :the upper case form of keyval, or keyval itself if it is already in upper case or it is not subject to case conversion.

gdk_keyval_to_lower ()

guint       gdk_keyval_to_lower             (guint keyval);

Converts a key value to lower case, if applicable.

keyval :a key value.
Returns :the lower case form of keyval, or keyval itself if it is already in lower case or it is not subject to case conversion.

gdk_keyval_is_upper ()

gboolean    gdk_keyval_is_upper             (guint keyval);

Returns TRUE if the given key value is in upper case.

keyval :a key value.
Returns :TRUE if keyval is in upper case, or if keyval is not subject to case conversion.

gdk_keyval_is_lower ()

gboolean    gdk_keyval_is_lower             (guint keyval);

Returns TRUE if the given key value is in lower case.

keyval :a key value.
Returns :TRUE if keyval is in lower case, or if keyval is not subject to case conversion.

gdk_keyval_to_unicode ()

guint32     gdk_keyval_to_unicode           (guint keyval);

Convert from a GDK key symbol to the corresponding ISO10646 (Unicode) character.

keyval : a GDK key symbol
Returns : the corresponding unicode character, or 0 if there is no corresponding character.

gdk_unicode_to_keyval ()

guint       gdk_unicode_to_keyval           (guint32 wc);

Convert from a ISO10646 character to a key symbol.

wc : a ISO10646 encoded character
Returns : the corresponding GDK key symbol, if one exists. or, if there is no corresponding symbol, wc | 0x01000000

Signals

The "direction-changed" signal

void        user_function                  (GdkKeymap *keymap,
                                            gpointer user_data);

The ::direction_changed signal gets emitted when the direction of the keymap changes.

keymap : the object on which the signal is emitted
user_data :user data set when the signal handler was connected.

Since 2.0


The "keys-changed" signal

void        user_function                  (GdkKeymap *keymap,
                                            gpointer user_data);

The ::keys_changed signal is emitted when the mapping represented by keymap changes.

keymap : the object on which the signal is emitted
user_data :user data set when the signal handler was connected.

Since 2.2