The issue is that MS Windows synthesizes a mouse-move event in response
to touch-move events, and those mouse-move events are NOT labeled as
coming from a touch (e.g. GetMouseMessageSource() will not return
SDL_MOUSE_EVENT_SOURCE_TOUCH for those synthesized mouse-move events).
In addition, there seems to be no way to prevent this from happening;
https://gist.github.com/vbfox/1339671 claims to demonstrate a technique
to prevent it, but in my experience, it doesn't work.
Because of this, the "fallthrough" case can't test that the synthesized
mouse-move came from a touch-move, and starts erroneously pressing down
the mouse-button, leading to massive confusion in the client
application.
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
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