1864174 - Window resizing issue when in full screen mode and while using external monitors

Status: UNCONFIRMED

(Core :: Widget: Cocoa, defect, P3)

Description

[mirai7865gm]

User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:109.0) Gecko/20100101 Firefox/119.0

Steps to reproduce:

(I am experiencing this issue on macOS Sonoma, but this issue has existed since macOS Sonoma, as much as I can remember. I am on 13-inch M2 MacBook Air.)

1. Make Firefox full screen.
2. Connect to an external screen, as an extended desktop.
3. Move the Firefox window to the external monitor.
4. Move the Firefox window back from the external monitor to the Mac screen.

Actual results:

I get vertical black bars at the both end of the screen, which seems to me that the Firefox window didn't get properly resized and macOS is filling up the leftover space in black.

Expected results:

The Firefox window should have been resized and use the screen fully to both ends.

Comment 1

[mirai7865gm]

Attachment: Before moving the Firefox window to the external monitor.

Comment 2

[mirai7865gm]

Attachment: After. Notice that the black space at left and right ends of the display are thicker.

Comment 3

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

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

Comment 4

[Stephen A Pohl [:spohl] (OOO until 7/30, contact :haik if urgent)]

I'm unable to see the attached images. Could you try uploading them again?

If you resize the window after moving it back to the internal screen, do the black bars disappear?

Comment 5

[mirai7865gm]

Yes, when I exit full screen, the black bars disappear.

Comment 6

[mirai7865gm]

Attachment: before.jpeg

Comment 7

[mirai7865gm]

Attachment: after.jpeg

Comment 8

[mirai7865gm]

I've re-uploaded the images. I hope they help others understand the situation better.

Comment 9

[mirai7865gm]

I found out what the issue was.
I've set up my mac to hide the menu bar while in full screen, and that was the culprit.
When I turned that setting off and forced to show the menu bar at all times, the issue went away.
It is very likely that Firefox is failing to properly rescale the window size while menu bar is hidden.