1994918 - Double clicking over top or bottom border of a window to vertical maximize stopped working

Status: RESOLVED FIXED

(Core :: Widget: Win32, defect)

Description

[csalsa]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:145.0) Gecko/20100101 Firefox/145.0

Steps to reproduce:

Move the mouse pointer to the top or bottom border of a window until the pointer turns into a double arrow, and double click/tap.

Actual results:

No change to window size

Expected results:

Window should have maximized vertically to screen but no change to horizontal width. Useful for very wide monitors.
This feature worked with previous versions of Firefox.

Comment 1

[csalsa]

Tested on MS-Windows 11 only.

Comment 2

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

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

Comment 3

[csalsa]

This is a Firefox regression on Windows. Not Android.
Windows keyboard shortcut still works (Windows + Shift + Up-Arrow) to vertically maximize a window
(Windows + Shift + Down-Arrow) to restore original window size and position

Comment 4

[Claude Gohier]

I confirm the issue on Windows 11.

Comment 5

[juraj.masiar]

Bisection result:
Bug 1947324 part 6 - avoid using Windows App SDK on opt-talos-xperf runs r=bobowen,perftest-reviewers,kshampur

On opt-talos-xperf, the Windows App SDK fails
calling DCompositionCreateDevice3() with ERROR_ACCESS_DENIED,
and the code assumes it is going to succeed so it proceeds to crash
deferencing null.

We haven't seen this crash anywhere else, and so I suspect this has
something to do with the way Firefox is being run there. So add a pref
to turn off using the Windows App SDK for just this test.

If this turns out to cause crashes in other situations, we should figure
out what the situation is and try to fix it.

Differential Revision: https://phabricator.services.mozilla.com/D267040

Comment 6

[juraj.masiar]

Could someone edit the "Regressed by" field and add there bug 1947324?
I don't have permissions for that.

Comment 7

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

:gstoll, since you are the author of the regressor, bug 1947324, could you take a look? Also, could you set the severity field?

For more information, please visit BugBot documentation.

Comment 8

[Greg Stoll :gstoll]

Note that this double-clicking does work on Chrome and Edge, but it doesn't work on Notepad or Windows Explorer.

Comment 9

[juraj.masiar]

That's interesting, maybe it's also a bug? :)
I always thought this is an OS feature.
It definitely works with all 3rd party apps I can currently find on my PC, including alternatives to the mentioned ones: "Notepad++" and "Q-Dir the Quad Explorer" :).

Comment 10

[Greg Stoll :gstoll]

The bug says this, but just a note to myself: this does not work for the left/right sides of the window (nor does it in Chrome, etc.)

Comment 11

[Greg Stoll :gstoll]

My potential fix for bug 1993474 seems to fix this too. (removing WS_BORDER)

Comment 14

[juraj.masiar]

Attachment: Screenshot 2025-11-28 195057.png

Does the fix for the bug 1993474 fix this issue?
I'm trying in the current Nightly but it doesn't seem to help, only the cursor now changes during double-click.
Also, maybe unrelated, the toolbar in the about:firefox modal is now totally broken - the close button is stretched over the whole bar. Can you see that too?

Comment 15

[Greg Stoll :gstoll]

Note that on the latest Nightly this works when the native titlebar is being shown (perhaps because of bug 2002986?), but it's still broken when tabs are in the titlebar. :emilio had an idea on how to fix this that I'm going to try.

(the about:firefox titlebar now looks fine to me on the latest nightly)

Comment 16

[Greg Stoll :gstoll]

Attachment: Bug 1994918 part 1 - fix double-clicking on top/bottom border on Windows r=emilio!

Something in the Windows App SDK's WNDPROC is causing the
double-clicking on the top/bottom border to not expand the window
vertically. (I suspect this is a bug, as this also happens in Notepad
with tabs in the titlebar)

So, similar to what we did in bug 1993474, don't even use the Windows
App SDK's WNDPROC as the previous WNDPROC to fall back to; instead, get
the previous WNDPROC before we call into the Windows App SDK and use
that.

Comment 17

[Greg Stoll :gstoll]

Attachment: Bug 1994918 part 2 - improve windows message debug output for WM_NCHITTEST r=#win-reviewers

Comment 18

[Greg Stoll :gstoll]

If we just redirect the WM_NCLBUTTONDBLCLK message, we can fix this in a less intrusive way.

Comment 19

[Emilio Cobos Álvarez [:emilio]]

Attachment: Bug 1994918 - Bypass windows app sdk handling of WM_NCLBUTTONDBLCLK. r=gstoll,#win-reviewers

Comment 20

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/8c456fb7974b
https://hg.mozilla.org/integration/autoland/rev/24bb5518fd1a
Bypass windows app sdk handling of WM_NCLBUTTONDBLCLK. r=gstoll,win-reviewers

Comment 21

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/24bb5518fd1a

Comment 22

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

The patch landed in nightly and beta is affected.
:gstoll, is this bug important enough to require an uplift?

• If yes, please nominate the patch for beta approval.
  • See https://wiki.mozilla.org/Release_Management/Requesting_an_Uplift for documentation on how to request an uplift.
• If no, please set status-firefox147 to wontfix.

For more information, please visit BugBot documentation.

Comment 23

[Greg Stoll :gstoll]

Attachment: Bug 1994918 - Bypass windows app sdk handling of WM_NCLBUTTONDBLCLK.

Original Revision: https://phabricator.services.mozilla.com/D275358

Comment 24

[Phabricator Automation]

firefox-beta Uplift Approval Request

• User impact if declined: Restores double-click functionality on Windows that has been broken since Fx 145.
• Code covered by automated testing: no
• Fix verified in Nightly: yes
• Needs manual QE test: no
• Steps to reproduce for manual QE testing: n/a
• Risk associated with taking this patch: low
• Explanation of risk level: Only affects the WM_NCLBUTTONDBLCLK message.
• String changes made/needed: no
• Is Android affected?: no

Comment 25

[Pulsebot]

https://github.com/mozilla-firefox/firefox/commit/068551b18925
https://hg.mozilla.org/releases/mozilla-beta/rev/f5d6015550d2

Comment 26

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/2ef746250dc8
https://hg.mozilla.org/integration/autoland/rev/3c5b868a606b
part 2 - improve windows message debug output for WM_NCHITTEST r=win-reviewers,handyman

Comment 27

[Cosmin Sabou [:CosminS]]

https://hg.mozilla.org/mozilla-central/rev/3c5b868a606b