input: Add support for making libxkbcommon optional

Graphics / Wayland / Weston - Matt Roper [intel.com] - 28 June 2013 18:55 UTC

In embedded environments, devices that appear as evdev "keyboards" often have no resemblence to PC-style keyboards. It is not uncommon for such environments to have no concept of modifier keys and no need for XKB key mapping; in these cases libxkbcommon initialization becomes unnecessary startup overhead. On some SOC platforms, xkb keymap compilation can account for as much as 1/3 - 1/2 of the total compositor startup time.

This patch introduces a 'use_xkbcommon' flag in the core compositor structure that indicates whether the compositor is running in "raw keyboard" mode. In raw keyboard mode, the compositor bypasses all libxkbcommon initialization and processing. 'key' events containing the integer keycode will continue to be delivered via the wl_keyboard interface, but no 'keymap' event will be sent to clients. No modifier handling or keysym mapping is performed in this mode.

Note that upstream sample apps (e.g., weston-terminal or the desktop-shell client) will not recognize raw keycodes and will not react to keypresses when the compositor is operating in raw keyboard mode. This is expected behavior; key events are still being sent to the client, the client (and/or its toolkit) just isn't written to handle keypresses without doing xkb keysym mapping. Applications written specifically for such embedded environments would be handling keypresses
via the raw keycode delivered as part of the 'key' event rather than using xkb keysym mapping.

Whether to use xkbcommon is a global option that applies to all compositor keyboard devices on the system; it is an all-or-nothing flag. This patch simply adds conditional checks on whether xkbcommon is to be used or not.

v3 don't send zero as the file descriptor - instead send the result of opening /dev/null

v2 by Rob Bradford : the original version of the patch used a "raw_keycodes" flag instead of the "use_xkbcommon" used in this patch.

01a9273 input: Add support for making libxkbcommon optional
src/compositor.c | 1 +
src/compositor.h | 3 +++
src/input.c | 74 ++++++++++++++++++++++++++++++++++++++----------------
3 files changed, 57 insertions(+), 21 deletions(-)

Upstream: cgit.freedesktop.org

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