Video Pauses or Resumes When Clicking Options Menu Items

[RcUchiha]

Tested by: Me and another person
Versions tested: 0.9.0-beta1 (release) and current Actions build 438fea9
Platform: Windows 11

While testing the latest builds, we noticed that clicking on items inside the “Options” menu sometimes causes the video to pause or resume on its own.

It’s not triggered by simply opening the menu — it only happens when clicking on one of its sections (e.g., Appearance..., Backup Settings..., Import Settings..., Language, etc.).

If the video was playing, it can suddenly pause.
If it was paused, it may start playing again unexpectedly.

The behavior doesn’t seem to follow a clear pattern, but it happens occasionally.
If you start clicking several of these menu items one after another, it tends to happen after a few tries.

Steps to Reproduce:

1. Open any video.
2. Play it (or pause it manually).
3. Open the Options menu.
4. Click various submenu items in sequence — e.g., Appearance..., Backup Settings..., Export Settings..., Language.
5. Observe that the video playback may pause or resume unexpectedly after some clicks.

Have a great day, @trin94 👋

[trin94]

Wow, I knew this day would happen 😉 Thanks for reporting this issue!

This is a bug in Qt that I've been tracking. I reported it upstream as QTBUG-131786, and another user independently reported it as QTBUG-133378.

I implemented a workaround in 701ccb3 even though I knew it was not working 100% reliably. My reasoning was that for typical QC workflows, these glitches would not happen often.

Unfortunately, there are only two paths forward:

1. Wait for Qt to fix the upstream bug (which we have no control over)
2. Change the video embedding architecture on Windows (which brings its own bag of issues and is objectively worse)

This is just one of the reasons mpvQC 0.9.0 is still in beta 🤷

[trin94]

I've experimented with a workaround in #242. If you have time, feel free to test a build. I'd be interested to know whether you can still trigger this issue. I could no longer reproduce it using any of the menus in the menubar or the new comment context menu.

Additional menus are affected as well: the menu when editing the comment type and the menu when configuring the time format in the footer. Since these are used even less frequently, I won't extend the workaround to cover them (it would require some additional complexity).

Background: All menus without drop-shadows are affected by this issue, as those are backed by native windows that Qt renders on top of. On Windows, we create a container for mpv to render video into that lives outside Qt Quick's rendering area. This means we cannot draw any item, menu, or popup over the video. The solution is to place anything that should appear on top of the video in a separate window. This feature was introduced in Qt Quick 6.7/6.8, which explains the bugs around it. QtWidgets uses the same concept but has had many years of optimization. Unfortunately, Qt Quick likely won't receive the same level of polish for many years, as Qt Quick's focus isn't primarily on desktop applications.

Linux renders the video directly into the scene, so we have no UI issues around the player and the UI is much more responsive. However, this approach has other issues and currently lacks a few features - though there's progress being made in the mpv repository. The Windows approach is better for the video itself -it's completely independent from our UI, which is the priority for quality checking. It's also the recommended way.

In any case, I'd be interested in your feedback in #242. However, we'll keep this issue open until it's resolved in Qt itself.

Best

[RcUchiha]

I tested the build from this PR on Windows, and so far I wasn’t able to reproduce the playback toggle issue anymore — even after repeatedly clicking through multiple menu items under “Options.”
Everything seems stable now.

Thanks for the detailed explanation and the quick workaround, @trin94.