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Bug 3198 - SDL_SetWindowSize oddness
Summary: SDL_SetWindowSize oddness
Status: ASSIGNED
Alias: None
Product: SDL
Classification: Unclassified
Component: render (show other bugs)
Version: 2.0.2
Hardware: x86_64 Linux
: P2 normal
Assignee: Ryan C. Gordon
QA Contact: Sam Lantinga
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2015-12-03 22:32 UTC by Solra Bizna
Modified: 2017-08-12 22:04 UTC (History)
0 users

See Also:

Attachments
Test program demonstrating the problem, written in C99 (3.81 KB, text/x-csrc)
2015-12-03 22:32 UTC, Solra Bizna 		Details
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Description Solra Bizna 2015-12-03 22:32:46 UTC 
Created attachment 2326 [details]
Test program demonstrating the problem, written in C99

When I change a window's size with SDL_SetWindowSize, and subsequently make SDL_Render* calls without processing events, the renderer gives incorrect output. It continues to give incorrect output until the SDL_WINDOWEVENT_EXPOSED event generated by the call is _received_. I have attached a program that demonstrates the problem.

I'm running on Linux, under X11, using Sawfish (a non-compositing window manager). The test program reports that the OpenGL renderer is being used.

The test program doesn't reflect this, but I tried combinations of SDL_RenderSetLogicalSize / SDL_RenderSetViewport and every similar function I could find with no effect.

If you change the "#if 0" on line 27 to "#if 1", it repeats Clear+Copy+Present every time a SDL_WINDOWEVENT_EXPOSED event is received, and the glitches effectively disappear. It also, however, hits a much less serious bug, in that an excessive number of SDL_WINDOWEVENT_EXPOSED events are generated. (A "good" event loop will defer actually rendering until SDL_PollEvent returns 0, which makes that bug unimportant to me.)

It is possible that this is not a bug, in which case the actual bug is in the documentation for SDL_SetWindowSize. It can be worked around completely by not rendering between calling SDL_SetWindowSize and receiving the corresponding SDL_WINDOWEVENT_EXPOSED event.
Comment 1 Solra Bizna 2016-01-03 14:36:05 UTC 
Upon testing with different renderers, I have found that SDL_WINDOWEVENT_EXPOSED is not always generated on calling SDL_SetWindowSize. My more universal workaround now also involves explicitly pushing an SDL_WINDOWEVENT_EXPOSED event after calling SDL_SetWindowSize. Blech...