ffplay 'maximize' toggle occasionally displays clipped rather than full image

[ahmogit]

Running ffplay version n7.1.1 on Arch linux, linked against libSDL2-2.0.so.0.3200.56 (the latter as supplied by Arch package ssdl2-compat 2.32.56-1), seeing the following intermittent behavior:

Occasionally, when the window is toggled from the maximized size to the original (reduced) size using the 'f' command, the reduced window does not display a smaller version of the entire image, as expected; instead, the reduced-size image consists of the lower-left corner of the maximized image. In other words, when this happens, the image in the reduced window is effectively a clipped version of the maximized view, rather than simply a reduced-size view of the entire image.

On my setup, the above-described behavior is intermittent, occuring roughly 10% to 20% of the time upon toggling from the maximized size back to the original image size.

If the above description is unclear, just let me know, will be happy to provide screenshots or video clip illustrating it clearly.

[slouken]

@Kontrabant, can you take a look at this?

[Kontrabant]

@ahmogit, could you give more details about your system, mainly your desktop environment and if it is X or Wayland (this sounds like buggy/racy X behavior, but need to be sure)?

[ahmogit]

@Kontrabant Sure, here's my setup:

Hardware:             Commodity x86_64 laptop
OS:                   Arch linux, recently synched to repos 
Windowing system:     Xorg 1.21.1.18
Window manager:       fvwm3  1.0.6a

I'm skeptical though that the observed behavior is due to X, since it does not occur with various older SDL2 versions, e.g. libSDL2-2.0.so.0.10.0.

It's also seems slightly peculiar that this viewport clipping behavior was never observed (at least by me) prior to libSDL2-2.0.so.3200.56, which fixes #10596, and was also related to toggling of the 'maximize' function. Perhaps worth examining whether the fix for #10596 might possibly have introduced this intermittent clipping behavior?

In any case, hypothesizing aside, I'll be happy to bisect further if you wish, just let me know. But my guess is that it will be reproducible for you with 2.32.56 if you have an X setup you can try it on.

[Kontrabant]

libSDL2-2.0.so.3200.56 is sdl2-compat running on top of SDL3, which had a lot of changes made to the windowing code. #10596 likely still occurs when running on top of the real SDL2 library, but was fixed in SDL3.

[ahmogit]

Ok.

Are there any testing implications for me, due to the fact that 2.32.56 is sdl2-compat? Glad to help if I can, but current ffplay does not link against SDL3 ABI afaik. Let me know if there's anything I can do on my end to narrow it down.

[Kontrabant]

I managed to reproduce this and have a fix, I just want to test it across more window managers first.

[ahmogit]

@Kontrabant Thank you for the quick response and fix on this, much appreciated.

Will test locally as soon as it becomes available in the Arch repos.