[Bug]: Exiting from fullscreen IFrame removes widgets from navbar

[Thesola10]

Pre-Submission Checklist

• [X] I have checked the existing/closed issues to ensure this issue has not already been reported.
• [X] I am using the latest supported version of the browser.
• [X] I have tried disabling all browser extensions/add-ons to rule out interference from these.
• [X] I have tried clearing the browser cache and cookies.
• [X] I have checked with a new profile and the issue still occurs.
• [X] I have provided detailed step-by-step instructions on how to reproduce the issue.
• [x] I have included relevant screenshots or console outputs.
• [X] I have checked that this problem is not occurring in the latest version of Firefox ESR.
• [X] This issue is specific to this browser and does not occur in other browsers.

Bug Summary

When full-screening a video player or something else, if the full screen component was contained within an <iframe> instead of directly on the root page, exiting from full screen has the navbar missing most buttons.

Entering and existing the "Customize toolbar" menu restores navigation buttons.

This does not affect cases where the full screen widget is part of the root page, such as the official YouTube website.

Reproduction Steps

1. Navigate to a website where the video player is an <iframe>, e.g. this DuckDuckGo search embed
2. Click on the 'full screen' button or equivalent on the video player
3. Exit from full screen

Expected Behavior

The navigation toolbar looks the same as before full screen

Actual Behavior

The navigation toolbar is missing most buttons and widgets

Screenshots

Before:

After:

Browser Version

11.18.1

Operating System

Arch Linux (Flatpak)

Additional Context

Desktop: GNOME 46 (Wayland) with fractional scaling 125% UI: Lepton, auto-hide sidebar, hide sidebar header, show sidebar on top, bottom navbar GPU: Intel Iris Xe (i7-1265U) No userChrome.css

[jonzn4suse]

I couldn't replicate the issue. Picked a video to watch on that site instead of going to youtube, clicked the full screen, then exited it, and my buttons are still there. What add-on is that black button with the number 10? My floorp is just running from the folder I downloaded it to. What desktop? X11 or Wayland?

Operating System: openSUSE Leap 15.6 KDE Plasma Version: 5.27.11 KDE Frameworks Version: 5.115.0 Qt Version: 5.15.12 Kernel Version: 6.4.0-150600.23.17-default (64-bit) Graphics Platform: X11 Processors: 16 × AMD Ryzen 7 PRO 6850HS with Radeon Graphics Memory: 62.1 GiB of RAM Graphics Processor: AMD Radeon Graphics Manufacturer: HP Product Name: HP EliteBook 865 16 inch G9 Notebook PC

[Thesola10]

@jonzn4suse updated with details on my platform

The addon is 10ten btw

[jonzn4suse]

I installed the add-on and had no issue. Download the browse to a folder, run floorp-bin and see if you have the same issue.

[Thesola10]

Found a log line that occurs repeatedly when the issue happens:

TypeError: aNode is null -- resource:///modules/CustomizableUI.sys.mjs:1724

browser.uiCustomization.debug does not yield more info

[Thesola10]

I've also confirmed that the issue happens with floorp-bin on the latest release artifact. By the way, I cleared browser.uiCustomization.state and re-created the browser UI by hand to ensure no weird stuff was in there, and the issue persists, so it is not related to which controls are present on the navbar.