gdk-Keyboard-Handling {RGtk2} | R Documentation

## Key Values

### Description

Functions for manipulating keyboard codes

### Methods and Functions

`gdkKeymapGetDefault()`
`gdkKeymapGetForDisplay(display)`
`gdkKeymapLookupKey(object, key)`
`gdkKeymapTranslateKeyboardState(object, hardware.keycode, state, group)`
`gdkKeymapGetEntriesForKeyval(object, keyval)`
`gdkKeymapGetEntriesForKeycode(object, hardware.keycode)`
`gdkKeymapGetDirection(object)`
`gdkKeymapHaveBidiLayouts(object)`
`gdkKeymapGetCapsLockState(object)`
`gdkKeymapAddVirtualModifiers(object)`
`gdkKeymapMapVirtualModifiers(object)`
`gdkKeyvalName(keyval)`
`gdkKeyvalFromName(keyval.name)`
`gdkKeyvalConvertCase(symbol)`
`gdkKeyvalToUpper(keyval)`
`gdkKeyvalToLower(keyval)`
`gdkKeyvalIsUpper(keyval)`
`gdkKeyvalIsLower(keyval)`
`gdkKeyvalToUnicode(keyval)`
`gdkUnicodeToKeyval(wc)`

### Hierarchy

    GObject
       +----GdkKeymap

### Detailed 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 ‘<gdk/gdk.h>’, it must be included independently, because the file is quite large.

Key values are regularly updated from the upstream X.org X11 implementation, so new values are added regularly. They will be prefixed with GDK_ rather than XF86XK_ or XK_ (for older symbols).

Key values can be converted into a string representation using `gdkKeyvalName`. The reverse function, converting a string to a key value, is provided by `gdkKeyvalFromName`.

The case of key values can be determined using `gdkKeyvalIsUpper` and `gdkKeyvalIsLower`. Key values can be converted to upper or lower case using `gdkKeyvalToUpper` and `gdkKeyvalToLower`.

When it makes sense, key values can be converted to and from Unicode characters with `gdkKeyvalToUnicode` and `gdkUnicodeToKeyval`.

One `GdkKeymap` object exists for each user display. `gdkKeymapGetDefault` returns the `GdkKeymap` for the default display; to obtain keymaps for other displays, use `gdkKeymapGetForDisplay`. 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 `gdkKeymapTranslateKeyboardState` 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 `gdkKeymapTranslateKeyboardState` 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 `gdkKeymapTranslateKeyboardState` just to get the keyval.

### Structures

`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`

  A `GdkKeymapKey` is a hardware key that can be mapped to a keyval. `GdkKeymapKey` is a transparent-type.

  `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.

### Signals

`direction-changed(keymap, user.data)`

  The ::direction-changed signal gets emitted when the direction of the keymap changes. Since 2.0

  `keymap`

    the object on which the signal is emitted

  `user.data`

    user data set when the signal handler was connected.

`keys-changed(keymap, user.data)`

  The ::keys-changed signal is emitted when the mapping represented by `keymap` changes. Since 2.2

  `keymap`

    the object on which the signal is emitted

  `user.data`

    user data set when the signal handler was connected.

`state-changed(keymap, user.data)`

  The ::state-changed signal is emitted when the state of the keyboard changes, e.g when Caps Lock is turned on or off. See `gdkKeymapGetCapsLockState`. Since 2.16

  `keymap`

    the object on which the signal is emitted

  `user.data`

    user data set when the signal handler was connected.

### Note

The keyval constants exist in RGtk2 as .gdkKeyvalName, so `.gdkPlus` for `plus`.

### Author(s)

Derived by RGtkGen from GTK+ documentation

### References

https://developer.gnome.org/gdk2/stable/gdk2-Keyboard-Handling.html

[Package RGtk2 version 2.20.36.3 Index]