Adds the SDL_EVENT_WINDOW_OCCLUDED events and the window flag SDL_WINDOW_OCCLUDED to report when the window occlusion state has changed, so that the application can take appropriate measures, as it may wish to suspend drawing, throttle, or otherwise behave in a more energy efficient manner when the window is not visible. When the window is no longer occluded, the SDL_EVENT_WINDOW_EXPOSED event is sent and the occlusion flag is cleared.
This is handled on macOS via the window occlusion state event (available as of 10.9), and via the xdg-shell protocol on Wayland (version 6, wayland-protocols 1.32, passed through in libdecor 0.1.2).
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