2003032 - Tabs in maximized window do not extend to top of screen

Status: RESOLVED DUPLICATE of bug 2004018

(Firefox :: Tabbed Browser, defect)

Description

[David Smith]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:147.0) Gecko/20100101 Firefox/147.0

Steps to reproduce:

Maximize window
Move cursor to top of screen over a tab
Click to select, or middle-click to close

Actual results:

Nothing

Expected results:

Tab should be selected or closed.

There appears to be about a 5 pixel gap between the top of the screen and the top of the tab. This breaks an expected Fitt's Law optimization.

Build 2025-11-27-21-35-32-mozilla-central works as expected. 11-28 build does not.

Comment 1

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

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

Comment 2

[Alice0775 White]

Bug 2002986 seems to fix this.

Comment 3

[Greg Stoll :gstoll]

I think this is actually a duplicate of bug 1993474 - either way, this seems to work in the latest Nightly.

Comment 4

[David Smith]

Just to note that it is still not fixed in the 12-01 build from today. Build ID: 20251201213546

It did work briefly on one window out of several, but did not work on the other windows. After updating the build, it doesn't work on any window. It does work in a new temp profile. It also works for my normal profile if settings widget.windows.windowsappsdk.enabled to false, despite the bug fix claiming that's no longer needed.

Comment 5

[Mathew Hodson]

Reopening since the reporter can still reproduce. Could be similar or the same as bug 2004018

Comment 6

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

:emilio, since you are the author of the regressor, bug 1993474, could you take a look?

For more information, please visit BugBot documentation.

Comment 7

[David Smith]

Just a note that as of build 20251207212832, behavior is still the same as in comment 4.

And from the comments in bug 2004018, it does appear to be the same thing.

Comment 8

[Emilio Cobos Álvarez [:emilio]]

Yeah I suspect this is basically bug 2004018, from the comments here.

Comment 9

[Emilio Cobos Álvarez [:emilio]]

Can you confirm latest nightly works as expected? Thanks.

Comment 10

[David Smith]

I can confirm that, with widget.windows.windowsappsdk.enabled back to the default of true, and on build 20251210095635, the problem no longer occurs.