Mouse warping coordinates are wrong in a maximized window
There is an issue with calculating coordinates to warp the mouse pointer. It's present in either a full-screen mode or in a maximized window when the aspect ratio of the display doesn't match the aspect ratio of the game's viewport. In this case the black fields are added to pad the game to the window. When I click any button the mouse pointer is warped towards the edge of the screen.
Looking at the warping code I believe the reason is that it doesn't take in account the possibility that the window size and the game's viewport size differ. But I lack any real understanding of SDL so I haven't figured out how to fix it yet.
So I thought I'd just file an issue and let you know. @amahl, tagging you as the author of the code in question.