gfx_sdl2/KDE: some window resizes lost, so doesn't draw over whole window & wrong mouse position

[rversteegen]

On Linux/KDE/X11 I've noticed that sometimes when I resize the window by dragging the corner gfx_sdl2 doesn't seem to tell the engine about the final window resize event (as if there's some lag while dragging and the last part of the drag gets lost), so it continues to draw a frame of the old size, which is somewhat off. This can result in black bars at the right and bottom of the window, and the mouse position gets miscalculated in get_image_origin_and_ratio. I haven't seen this happen on Windows.

[rversteegen]

This doesn't happen under xfce4. I was running KDE 4 at the time, but my distro has since upgraded to KDE 5, and it's still happening on that, including under latest SDL git.

Through trial and error, after comparing with a simple test program that didn't suffer this problem, I figured out that the problem is calling SDL_SetWindowSize while the user is resizing the window. I'm fixed this by skipping the SDL_SetWindowSize in that case.

This bug sounds like the same thing as another bug I noticed in gfx_sdl/sdl2 (under at least xfce4), where if the user is resizing the window (or at least has the mouse button held down on the window frame) at the moment the engine tries to resize the window (e.g. on starting a game) then it doesn't resize properly. But that doesn't happen if the window isn't resizable either before or after the forced-resize, so it's very minor and I'll ignore it.