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When possible use native os functions to make a blocking call waiting for an incoming event. Previous behavior was to continuously poll the event queue with a small delay between each poll. The blocking call uses a new optional video driver event, WaitEventTimeout, if available. It is called only if an window already shown is available. If present the window is designated using the variable wakeup_window to receive a wakeup event if needed. The WaitEventTimeout function accept a timeout parameter. If positive the call will wait for an event or return if the timeout expired without any event. If the timeout is zero it will implement a polling behavior. If the timeout is negative the function will block indefinetely waiting for an event. To let the main thread sees events sent form a different thread a "wake-up" signal is sent to the main thread if the main thread is in a blocking state. The wake-up event is sent to the designated wakeup_window if present. The wake-up event is sent only if the PushEvent call is coming from a different thread. Before sending the wake-up event the ID of the thread making the blocking call is saved using the variable blocking_thread_id and it is compared to the current thread's id to decide if the wake-up event should be sent. Two new optional video device methods are introduced: WaitEventTimeout SendWakeupEvent in addition the mutex wakeup_lock which is defined and initialized but only for the drivers supporting the methods above. If the methods are not present the system behaves as previously performing a periodic polling of the events queue. The blocking call is disabled if a joystick or sensor is detected and falls back to previous behavior.
Simple DirectMedia Layer (SDL) Version 2.0
Simple DirectMedia Layer is a cross-platform development library designed to provide low level access to audio, keyboard, mouse, joystick, and graphics hardware via OpenGL and Direct3D. It is used by video playback software, emulators, and popular games including Valve's award winning catalog and many Humble Bundle games.
More extensive documentation is available in the docs directory, starting with README.md
Enjoy!
Sam Lantinga (slouken@libsdl.org)