Using IOKit for this pops up a warning at startup on macOS 10.15 ("Catalina"),
asking the user to authorize the app to listen to all keyboard input in the
system, which is unacceptable.
I _think_ we were using IOKit under incorrect presumptions here; the Stack
Overflow link mentioned in it was complaining about not being able to use
flagsChanged to differentiate between left and right mod keys, but that's not
an issue for capslock.
It's also possible this code was trying to deal with capslock changing when
the window didn't have focus, but we handle this elsewhere now, if we didn't
at the time.
Tim McDaniel
Using checkkeys test app:
* Press and hold Caps Lock key.
* checkkeys reports a CapsLock key pressed event and a CapsLock key released event.
* Release Caps Lock key.
* checkkeys reports no further events.
This patch fixes OSX Caps Lock up/down event detection by installing a HID callback.
The internal function SDL_EGL_LoadLibrary() did not delete and remove a mostly
uninitialized data structure if loading the library first failed. A later try to
use EGL then skipped initialization and assumed it was previously successful
because the data structure now already existed. This led to at least one crash
in the internal function SDL_EGL_ChooseConfig() because a NULL pointer was
dereferenced to make a call to eglBindAPI().
Cameron Gutman
Sam Lantinga
Ryan C. Gordon
Alex Szpakowski
Philipp Wiesemann