player: add --auto-window-resize option

[Dudemanguy]

mpv's window resizing logic always automatically resized the window
whenever the video resolution changed (i.e. advancing forward in a
playlist). This simply introduces the option to make this behavior
configurable. Every windowing backend would need to implement this
behavior in their code. This commit implements it for Wayland and X11.

Related issue: #9325

[Dudemanguy]

Sadly, the x11 change is no longer one line because the autofit/geometry stuff also must execute vo_x11_config_vo_window. It should work as intended now though.

[Akemi]

i am just wondering, wouldn't it make more sense to do this deeper in the core instead of the platform specific code or is there a specific reason why we want ti implemented on every platform separately?

[Dudemanguy]

I did initially attempt to do this by just messing with player/video.c and/or vo.c, but I didn't think there was a sane/clean way to do it it. Or at least, I couldn't think of one anyway. In player/video.c, mpv will do a check if the vo->params are not equal to the params from the incoming frame and thus trigger a reconfig (vo_reconfig2) in the vo which propagates downwards to every backend. This is the source of mpv's automatic resizing behavior. You can, of course, not do the reconfig and ensure the window won't change its size but that doesn't change the fact that the new frame is of a different size than the previous one. In practice, this means that the picture will be cut off if you go from a smaller resolution to a bigger one (didn't try the reverse actually).

So as far as I can tell, this requires the reconfig call which calls a resize (this is the part that's really needed) and the only way that can be done is by propagating to every backend.

[Dudemanguy]

I took a peek at the windows code and I think the required change is trivial so I went ahead and added it to this.

[occivink]

Another relevant case is when setting video-aspect-override, the window is automatically resized to match the new video ratio and avoid black bars.
With this new option enabled, the window size stays the same as expected.

[Dudemanguy]

P.S. if someone could test if the Windows change actually works correctly, that would be nice. mac was left out since swift makes my head spin.

[dyphire]

I tested it on windows, and the option of auto-window-resize works correctly.

[Dudemanguy]

Thanks for confirming. I think this is OK to merge (unless there's still some disagreements over the implementation). It's missing mac support, but no one can do that other than @Akemi anyways.

[anonish]

I have always used

geometry=1920x1080+0+0
no-keepaspect-window
force-window=yes
keep-open=yes
idle=yes

and never had the window auto-resize on me on switching videos (either through playlist skip, playlist end, or dragging a new video into the window), is this going to change anything?

[Dudemanguy]

For your configuration, no. The main thing this does is prevent auto-resizing without having to specify an arbitrary geometry (i.e. it'll just stay at whatever the first value in the playlist happens to be).

[Dudemanguy]

People still ping me about this occasionally and it's a useful feature so I plan to finally merge it soonish in case anyone wants to take another look at it.