EmuWindow::PollEvents was called from the GPU thread (or the CPU thread
in sync-GPU mode) when swapping buffers. It had three implementations:
- In GRenderWindow, it didn't actually poll events, just set a flag and
emit a signal to indicate that a frame was displayed.
- In EmuWindow_SDL2_Hide, it did nothing.
- In EmuWindow_SDL2, it did call SDL_PollEvents, but this is wrong
because SDL_PollEvents is supposed to be called on the thread that set
up video - in this case, the main thread, which was sleeping in a
busyloop (regardless of whether sync-GPU was enabled). On macOS this
causes a crash.
To fix this:
- Rename EmuWindow::PollEvents to OnFrameDisplayed, and give it a
default implementation that does nothing.
- In EmuWindow_SDL2, do not override OnFrameDisplayed, but instead have
the main thread call SDL_WaitEvent in a loop.
Abstracts most of the input mechanisms under an InputSubsystem class
that is managed by the frontends, eliminating any static constructors
and destructors. This gets rid of global accessor functions and also
allows the frontends to have a more fine-grained control over the
lifecycle of the input subsystem.
This also makes it explicit which interfaces rely on the input subsystem
instead of making it opaque in the interface functions. All that remains
to migrate over is the factories, which can be done in a separate
change.
