1833407 - Tab toolbar has some space where the firefox window cannot grabbed using the mouse, when customized to include flexible space

Status: NEW

(Core :: Widget: Win32, defect, P3)

Description

[transsive]

Attachment: firefox drag and drop.png

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/113.0

Steps to reproduce:

I use the mouse to move the Firefox window between monitors. (click and drag in the empty space after last open tab)
When many tabs are open, it seems there is a space of several pixels at the top where the mouse click will not be picked up. (see attached picture)

Actual results:

Mouse click and drag is ignored

Expected results:

Mouse click and drag should move firefox window

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

[Monica Chiorean]

Mark as new for dev team to add their input on this issue(I see same issue on FF 77.0a1(20200429215539)). Thank you for your report.

Comment 3

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

The severity field is not set for this bug.
:dao, could you have a look please?

For more information, please visit BugBot documentation.

Comment 4

[Dão Gottwald [:dao]]

Can you reproduce this in a new profile? It looks like you may have customized Firefox by dragging stuff into the tab strip and enabling compact mode. It would be good to know if one of those things is a factor in this.

Comment 5

[transsive]

Yes, I managed to reproduce it in a new profile.
Turns out it is linked to the 'Flexible Space' item in the customize menu.
Once a 'Flexible Space' is added between the last tab and the new tab button '+', a small dead zone in created in the top row pixels (when the windows is maximized).
With normal density the area is even bigger.

It can only be reproduced in a maximized window. The window cannot be grabbed from those pixels. See new attachment.

Comment 6

[transsive]

Attachment: bug-replicate.png

windows needs to be maximized, flexible space creates an area where the browser window cannot be grabbed

Comment 7

[:Gijs (he/him)]

Feels like the flexible space should "just" stretch when it's in the tabstrip, in order to remedy this, but not sure if that's straightforward. Will try to look at this when my Windows machine is back up and running.

Comment 8

[:Gijs (he/him)]

Attachment: Inspector of flexible space

It looks like this isn't as easy as I hoped; the flexible space is already the right size. It's not clear to me why some of the pixels don't respond to dragging. It's also odd that this problem is happening for a few px height on the left (start) side of the flexible space, but not along its entire width, at least in my testing (ie the right-hand side of the space does not have this dead space).

I'm guessing this is something to do with how we compute the drag area internally and where we think the window border is, but I'm not in a position to investigate this further at the moment, and given the relative size of the issue and the fact that there aren't flexible spaces in the tabstrip by default, I'm not sure that it'd be a priority soon...

Comment 9

[:Gijs (he/him)]

Oh, and perhaps worth noting: I tried setting -moz-window-dragging: drag on the flexible space explicitly, but this made no difference.

Comment 10

[Ray Kraesig [:rkraesig]]

(I'd have thought this was a DOM bug from the sound of it, but I've tried and failed to repro under KDE.)