gtk2/docs/reference/gdk/tmpl/keys.sgml

<!-- ##### SECTION Title ##### -->
Key Values

<!-- ##### SECTION Short_Description ##### -->
Functions for manipulating keyboard codes

<!-- ##### SECTION Long_Description ##### -->
<para>
Key values are the codes which are sent whenever a key is pressed or released.
They appear in the <structfield>keyval</structfield> 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 <filename>&lt;gdk/gdkkeysyms.h&gt;</filename>
header file. <filename>&lt;gdk/gdkkeysyms.h&gt;</filename> is not included in <filename>&lt;gtk/gtk.h&gt;</filename>, 
it must be included independently, because the file is quite large.
</para>
<para>
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().
</para>
<para>
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().
</para>
<para>
When it makes sense, key values can be converted to and from 
Unicode characters with gdk_keyval_to_unicode() and gdk_unicode_to_keyval().
</para>

<para>
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
<firstterm>level</firstterm> 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.
</para>

<para>
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.
</para>

<para>
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.

</para>

<!-- ##### SECTION See_Also ##### -->
<para>

</para>

<!-- ##### STRUCT GdkKeymap ##### -->
<para>
A <structname>GdkKeymap</structname> 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.
</para>


<!-- ##### STRUCT GdkKeymapKey ##### -->
<para>
A <structname>GdkKeymapKey</structname> is a hardware key that can 
be mapped to a keyval.
</para>

@keycode: the hardware keycode. This is an identifying number for a 
  physical key.
@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.
@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.

<!-- ##### FUNCTION gdk_keymap_get_default ##### -->
<para>

</para>

@Returns: 


<!-- ##### FUNCTION gdk_keymap_get_for_display ##### -->
<para>

</para>

@display: 
@Returns: 


<!-- ##### FUNCTION gdk_keymap_lookup_key ##### -->
<para>

</para>

@keymap: 
@key: 
@Returns: 


<!-- ##### FUNCTION gdk_keymap_translate_keyboard_state ##### -->
<para>

</para>

@keymap: 
@hardware_keycode: 
@state: 
@group: 
@keyval: 
@effective_group: 
@level: 
@consumed_modifiers: 
@Returns: 
<!-- # Unused Parameters # -->
@unused_modifiers: 


<!-- ##### FUNCTION gdk_keymap_get_entries_for_keyval ##### -->
<para>

</para>

@keymap: 
@keyval: 
@keys: 
@n_keys: 
@Returns: 


<!-- ##### FUNCTION gdk_keymap_get_entries_for_keycode ##### -->
<para>

</para>

@keymap: 
@hardware_keycode: 
@keys: 
@keyvals: 
@n_entries: 
@Returns: 


<!-- ##### FUNCTION gdk_keymap_get_direction ##### -->
<para>
Returns the direction of the keymap. 
</para>

@keymap: a #GdkKeymap or %NULL to use the default keymap.
Returns: %PANGO_DIRECTION_LTR or %PANGO_DIRECTION_RTL.
@Returns: the direction of the keymap.


<!-- ##### FUNCTION gdk_keyval_name ##### -->
<para>
Converts a key value into a symbolic name.
The names are the same as those in the <filename>&lt;gdk/gdkkeysyms.h&gt;</filename> header file
but without the leading "GDK_".
</para>

@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.


<!-- ##### FUNCTION gdk_keyval_from_name ##### -->
<para>
Converts a key name to a key value.
</para>

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


<!-- ##### FUNCTION gdk_keyval_convert_case ##### -->
<para>

</para>

@symbol: 
@lower: 
@upper: 


<!-- ##### FUNCTION gdk_keyval_to_upper ##### -->
<para>
Converts a key value to upper case, if applicable.
</para>

@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.


<!-- ##### FUNCTION gdk_keyval_to_lower ##### -->
<para>
Converts a key value to lower case, if applicable.
</para>

@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.


<!-- ##### FUNCTION gdk_keyval_is_upper ##### -->
<para>
Returns %TRUE if the given key value is in upper case.
</para>

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


<!-- ##### FUNCTION gdk_keyval_is_lower ##### -->
<para>
Returns %TRUE if the given key value is in lower case.
</para>

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


<!-- ##### FUNCTION gdk_keyval_to_unicode ##### -->
<para>

</para>

@keyval: 
@Returns: 


<!-- ##### FUNCTION gdk_unicode_to_keyval ##### -->
<para>

</para>

@wc: 
@Returns: 


<!-- ##### SIGNAL GdkKeymap::direction-changed ##### -->
<para>

</para>

@keymap: the object which received the signal.


<!-- ##### SIGNAL GdkKeymap::keys-changed ##### -->
<para>

</para>

@keymap: the object which received the signal.