SDL_SetKeyboardFocus(NULL) will lift any keys still pressed when keyboard focus
leaves the window, but then key repeat comes behind our backs and presses the
key down again. This results in an infinite stream of SDL_KEYDOWN events when
focus leaves the window with a key down (particularly noticeable with Alt+Tab).
This gives us flexibility to add others hints to control keyboard grab behavior
without having to touch all of the backends. It also allows us to possibly
expose keyboard grab separately from mouse grab for applications that want to
manage those independently.
These are explicitly written in C code rather than generated at build
time, so they weren't affected by changing how we invoke
wayland-scanner.
Signed-off-by: Simon McVittie <smcv@collabora.com>
We support both the org.freedesktop.ScreenSaver D-Bus API (same as the X11
backend) and the Wayland idle_inhibit_unstable_v1 protocol.
Some Wayland compositors only support one or the other, so we need both to
for broad compatibility.
Wayland compositors seem to have standardized on 10 units per "wheel tick" for
continuous scroll events, so we need to convert these axis values to ticks by
dividing by 10 before reporting them in SDL_MOUSEWHEEL events.
This is implemented via a low-level keyboard hook. Unfortunately, this is
rather invasive, but it's how Microsoft recommends that it be done [0].
We want to do as little as possible in the hook, so we only intercept a few
crucial modifier keys there, while leaving other keys to the normal event
processing flow.
We will only install this hook if SDL_HINT_GRAB_KEYBOARD=1, which is not
the default. This will reduce any compatibility concerns to just the SDL
applications that explicitly ask for this behavior.
We also remove the hook when the grab is terminated to ensure that we're
not unnecessarily staying involved in key event processing when it's not
required anymore.
[0]: https://docs.microsoft.com/en-us/windows/win32/dxtecharts/disabling-shortcut-keys-in-games
Hiding the cursor doesn't appear to work reliably on GNOME when another window
steals mouse focus right as we call SDL_ShowCursor(SDL_DISABLE). This can happen
when the keyboard shortcut inhibition permission prompt appears in response to a
call to SDL_SetRelativeMouseMode() with SDL_HINT_GRAB_KEYBOARD=1. The result is
that the default cursor is stuck locked in position and visible on screen
indefinitely.
By redrawing the cursor on pointer focus enter, the cursor now disappears upon
the first mouse motion event. It's not perfect but it's way better than the
current behavior.
Use zwp_keyboard_shortcuts_inhibit_manager_v1 to allow SDL applications
to capture system keyboard shortcuts like Alt+Tab when keyboard grab is
enabled via SDL_HINT_GRAB_KEYBOARD.
Existing SDL applications may not know about the need to set a specific
hint to enable rumble on PS5 controllers, even though they may already
set the equivalent SDL_HINT_JOYSTICK_HIDAPI_PS4_RUMBLE hint for PS4
controller rumble support.
Rather than requiring those developers update their apps, let's use the
SDL_HINT_JOYSTICK_HIDAPI_PS4_RUMBLE value as an indication of the behavior
they are expected for all PlayStation controllers.
From hidapi mainstream git: https://github.com/libusb/hidapi/issues/142d2c3a9862e
Read callback may fire itself on its own even after its been requested
to stop and exactly before the calling code waits for its completion in
indefinite loop. Explicitly preventing re-fireing the submission loop
fixes the issue.
