X11 support

## Macros

#define | XKB_X11_MIN_MAJOR_XKB_VERSION 1
#define | XKB_X11_MIN_MINOR_XKB_VERSION 0

## Enumerations

enum | xkb_x11_setup_xkb_extension_flags { XKB_X11_SETUP_XKB_EXTENSION_NO_FLAGS = 0 }

## Functions

int | xkb_x11_setup_xkb_extension (xcb_connection_t *connection, uint16_t major_xkb_version, uint16_t minor_xkb_version, enum xkb_x11_setup_xkb_extension_flags flags, uint16_t *major_xkb_version_out, uint16_t *minor_xkb_version_out, uint8_t *base_event_out, uint8_t *base_error_out)
int32_t | xkb_x11_get_core_keyboard_device_id (xcb_connection_t *connection)
struct xkb_keymap * | xkb_keymap::xkb_x11_keymap_new_from_device (struct xkb_context *context, xcb_connection_t *connection, int32_t device_id, enum xkb_keymap_compile_flags flags)
struct xkb_state * | xkb_state::xkb_x11_state_new_from_device (struct xkb_keymap *keymap, xcb_connection_t *connection, int32_t device_id)

## Detailed Description

Additional X11 support for xkbcommon.

Since
  0.4.0

### Overview

The xkbcommon-x11 module provides a means for creating an xkb_keymap corresponding to the currently active keymap on the X server. To do so, it queries the XKB X11 extension using the xcb-xkb library. It can be used as a replacement for Xlib's keyboard handling.

Following is an example workflow using xkbcommon-x11. A complete example may be found in the test/interactive-x11.c file in the xkbcommon source repository. On startup:

1. Connect to the X server using xcb_connect().
2. Setup the XKB X11 extension. You can do this either by using the xcb_xkb_use_extension() request directly, or by using the xkb_x11_setup_xkb_extension() helper function.

The XKB extension supports using separate keymaps and states for different keyboard devices. The devices are identified by an integer device ID and are managed by another X11 extension, XInput (or its successor, XInput2). The original X11 protocol only had one keyboard device, called the "core keyboard", which is still supported as a "virtual device".

1. We will use the core keyboard as an example. To get its device ID, use either the xcb_xkb_get_device_info() request directly, or the xkb_x11_get_core_keyboard_device_id() helper function.
2. Create an initial xkb_keymap for this device, using the xkb_x11_keymap_new_from_device() function.
3. Create an initial xkb_state for this device, using the xkb_x11_state_new_from_device() function.

Note
  At this point, you may consider setting various XKB controls and XKB per-client flags. For example, enabling detectable autorepeat:
  http://www.x.org/releases/current/doc/kbproto/xkbproto.html#Detectable_Autorepeat

Next, you need to react to state changes (e.g. a modifier was pressed, the layout was changed) and to keymap changes (e.g. a tool like xkbcomp, setxkbmap or xmodmap was used):

1. Select to listen to at least the following XKB events: NewKeyboardNotify, MapNotify, StateNotify; using the xcb_xkb_select_events_aux() request.
2. When NewKeyboardNotify or MapNotify are received, recreate the xkb_keymap and xkb_state as described above.
3. When StateNotify is received, update the xkb_state accordingly using the xkb_state_update_mask() function.

Note
  It is also possible to use the KeyPress/KeyRelease `state` field to find the effective modifier and layout state, instead of using XkbStateNotify:
  http://www.x.org/releases/current/doc/kbproto/xkbproto.html#Computing_A_State_Field_from_an_XKB_State
  However, XkbStateNotify is more accurate.
  There is no need to call xkb_state_update_key(); the state is already synchronized.

Finally, when a key event is received, you can use ordinary xkbcommon functions, like xkb_state_key_get_one_sym() and xkb_state_key_get_utf8(), as you normally would.

## Enumeration Type Documentation

enum xkb_x11_setup_xkb_extension_flags

Flags for the xkb_x11_setup_xkb_extension() function.

Enumerator
XKB_X11_SETUP_XKB_EXTENSION_NO_FLAGS | Do not apply any flags.

## Function Documentation

int xkb_x11_setup_xkb_extension | ( | xcb_connection_t * | connection,
|  | uint16_t | major_xkb_version,
|  | uint16_t | minor_xkb_version,
|  | enum xkb_x11_setup_xkb_extension_flags | flags,
|  | uint16_t * | major_xkb_version_out,
|  | uint16_t * | minor_xkb_version_out,
|  | uint8_t * | base_event_out,
|  | uint8_t * | base_error_out
| ) |  |

Setup the XKB X11 extension for this X client.

The xkbcommon-x11 library uses various XKB requests. Before doing so, an X client must notify the server that it will be using the extension. This function (or an XCB equivalent) must be called before any other function in this library is used.

Some X servers may not support or disable the XKB extension. If you want to support such servers, you need to use a different fallback.

You may call this function several times; it is idempotent.

Parameters

  | connection | An XCB connection to the X server.
  | major_xkb_version | See `minor_xkb_version`.
  | minor_xkb_version | The XKB extension version to request. To operate correctly, you must have (major_xkb_version, minor_xkb_version) >= (XKB_X11_MIN_MAJOR_XKB_VERSION, XKB_X11_MIN_MINOR_XKB_VERSION), though this is not enforced.
  | flags | Optional flags, or 0.
  [out] | major_xkb_version_out | See `minor_xkb_version_out`.
  [out] | minor_xkb_version_out | Backfilled with the compatible XKB extension version numbers picked by the server. Can be NULL.
  [out] | base_event_out | Backfilled with the XKB base (also known as first) event code, needed to distinguish XKB events. Can be NULL.
  [out] | base_error_out | Backfilled with the XKB base (also known as first) error code, needed to distinguish XKB errors. Can be NULL.

Returns
  1 on success, or 0 on failure.

int32_t xkb_x11_get_core_keyboard_device_id | ( | xcb_connection_t * | connection | ) |

Get the keyboard device ID of the core X11 keyboard.

Parameters

  connection | An XCB connection to the X server.

Returns
  A device ID which may be used with other xkb_x11_* functions, or -1 on failure.

struct xkb_keymap * xkb_x11_keymap_new_from_device | ( | struct xkb_context * | context,
|  | xcb_connection_t * | connection,
|  | int32_t | device_id,
|  | enum xkb_keymap_compile_flags | flags
| ) |  |

Create a keymap from an X11 keyboard device.

This function queries the X server with various requests, fetches the details of the active keymap on a keyboard device, and creates an xkb_keymap from these details.

Parameters

  context | The context in which to create the keymap.
  connection | An XCB connection to the X server.
  device_id | An XInput 1 device ID (in the range 0-255) with input class KEY. Passing values outside of this range is an error.
  flags | Optional flags for the keymap, or 0.

Returns
  A keymap retrieved from the X server, or NULL on failure.

struct xkb_state * xkb_x11_state_new_from_device | ( | struct xkb_keymap * | keymap,
|  | xcb_connection_t * | connection,
|  | int32_t | device_id
| ) |  |

Create a new keyboard state object from an X11 keyboard device.

This function is the same as xkb_state_new(), only pre-initialized with the state of the device at the time this function is called.

Parameters

  keymap | The keymap for which to create the state.
  connection | An XCB connection to the X server.
  device_id | An XInput 1 device ID (in the range 0-255) with input class KEY. Passing values outside of this range is an error.

Returns
  A new keyboard state object, or NULL on failure.