## Key Values

Key Values — Functions for manipulating keyboard codes

## Synopsis

    #include <gdk/gdk.h>

    struct      GdkKeymap;
    struct      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 *gdkkeymap,
                                                gpointer user_data);
    "keys-changed"
                void        user_function      (GdkKeymap *gdkkeymap,
                                                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. 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;

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.

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.

`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 : |

### 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 *gdkkeymap,
                                                gpointer user_data);

### The "keys-changed" signal

    void        user_function                  (GdkKeymap *gdkkeymap,
                                                gpointer user_data);