1872943 - Full-screen video only occupies top-left quarter of the screen with Wayland, 200% scaling and customized full-screen-api.transition-duration.enter

Status: RESOLVED DUPLICATE of bug 1869724

(Core :: Widget: Gtk, defect)

Description

[Dmitry Gutov]

Attachment: about-support.txt

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:122.0) Gecko/20100101 Firefox/122.0

Steps to reproduce:

To make the problem appear in a new profile, I just need to add

user_pref("full-screen-api.transition-duration.enter", "100 100");

to its prefs.js. It took a while to bisect my config to find this, and it seems like it's been living for a while in my personal profile.

Other conditions:

• GNOME 45.1 (Ubuntu 22.10) with Wayland
• Run as GDK_BACKEND=wayland firefox
• Display scale is 200% and fractional scaling is disabled.

Visit a Youtube video, or e.g. a Steam's web page for some game.
Start playback, then press 'F' to toggle full screen.

Actual results:

The video is displaced by a half-screen up and to the left. The result is that it's visible only in the top-left quarter of the screen (the bottom-right quarter of the video). The remainder of the screen is black.

Screenshot: https://imgur.com/xlZ8d58

Expected results:

The video frame should occupy the full screen, with all of it being visible.

Changes that make this bug go away (any one of these is sufficient):

• Enabling fractional scaling in GNOME's settings (while keeping the scale 200%).
• Using GDK_BACKEND=x11 rather than native Wayland.
• Entering the full screen first with (F11) - then the behavior is also buggy, but it's https://bugzilla.mozilla.org/show_bug.cgi?id=1869724 instead (all screen is covered by only a quarter of the video).
• Or removing the 'full-screen-api.transition-duration.enter' pref, of course.

This bug is particularly treacherous IMO since this preference doesn't appear in the list or "Important Modified Preferences" in about:support.

Comment 1

[Dmitry Gutov]

Sorry, it's Ubuntu 23.10, not 22.10.

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

The Bugbug bot thinks this bug should belong to the 'Core::Widget: Gtk' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.