This fixes once and for all the core issue of different Godot `keycode`s
released from the same raw XKB keycode.
The `InputEventKey` `keycode` value _should_ map to the "unmodified"
key, but unfortunately there's an ambiguity with their encoding for
"special" keys ("delete", "insert", etc.), in witch they ignore their
unicode representation. This means that a key that is special when plain
but a character when modified would never be properly picked up, so we
do indeed change its keycode. As a consequence of this exception, some
Godot keys never receive release events and get "stuck".
This patch adds an extra check through an `HashMap` to "unstuck" keys
that changed while having the same keycode.
I also could not resist simplifying a bit the regular key event
generation method but this makes things more consistent and predictable
IMO.
The `keycode` field of `InputEventKey` is supposed to be "unshifted";
That is, what the key would output if no modifier keys were pressed.
This should match what's written on the key label, but `Key` enumerates
also all keypad keys, which require a modifier. We thus require some
extra checks for them.
Note that this can still allow "stuck keys", but that's an even deeper
problem.
Not everything is yet implemented, either for Godot or personal
limitations (I don't have all hardware in the world). A brief list of
the most important issues follows:
- Single-window only: the `DisplayServer` API doesn't expose enough
information for properly creating XDG shell windows.
- Very dumb rendering loop: this is very complicated, just know that
the low consumption mode is forced to 2000 Hz and some clever hacks are
in place to overcome a specific Wayland limitation. This will be
improved to the extent possible both downstream and upstream.
- Features to implement yet: IME, touch input, native file dialog,
drawing tablet (commented out due to a refactor), screen recording.
- Mouse passthrough can't be implement through a poly API, we need a
rect-based one.
- The cursor doesn't yet support fractional scaling.
- Auto scale is rounded up when using fractional scaling as we don't
have a per-window scale query API (basically we need
`DisplayServer::window_get_scale`).
- Building with `x11=no wayland=yes opengl=yes openxr=yes` fails.
This also adds a new project property and editor setting for selecting the
default DisplayServer to start, to allow this backend to start first in
exported projects (X11 is still the default for now). The editor setting
always overrides the project setting.
Special thanks to Drew Devault, toger5, Sebastian Krzyszkowiak, Leandro
Benedet Garcia, Subhransu, Yury Zhuravlev and Mara Huldra.
