1933526 - With RFP/letterboxing enabled Firefox moves part of the window offscreen every second start

Status: RESOLVED DUPLICATE of bug 1934238

(Core :: Privacy: Anti-Tracking, defect)

Description

[sworddragon2]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:133.0) Gecko/20100101 Firefox/133.0

Steps to reproduce:

1. Set privacy.resistFingerprinting and privacy.resistFingerprinting.letterboxing to true.
2. Restart Firefox.
3. Maximize the window with the square button on the top right.
4. Close Firefox and start it again.
5. Optionally maximize the window again and repeat by going back to step 2.

Actual results:

After one start of Firefox the window will be a bit offscreen while on the other start it will be fully onscreen. This behavior will cycle through if the window will be maximized so that on every second start of Firefox the window will be a bit offscreen again.

Expected results:

The window should correctly restore its last position.

Additional details:

This issue was introduced after updating Firefox to version 133.0. Another change but possibly unrelated: The default size for the window in this mode got increased as well.

Comment 1

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

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

Comment 2

[Manuel Bucher [:manuel]]

Thanks for your report!
Could you please try to narrow down the regression range with mozregression (hopefully to a single bug)?

• https://mozilla.github.io/mozregression
• https://mozilla.github.io/mozregression/documentation/usage.html

./mach mozregression --pref privacy.resistFingerprinting:true privacy.resistFingerprinting.letterboxing:true --profile-persistence clone-first --good 132 --bad 133

you can use the retry command to simulate the restarting firefox.

Comment 3

[sworddragon2]

I fear I'm too busy to do a mozregression for this minor bug in the future - for now I leave it as it is.

Comment 4

[Emma Zühlcke [:emz]]

I can't reproduce this issue. Manuel, have you tried to reproduce? I wonder if it's Windows specific. Would should try to confirm the bug if possible. Thanks!

Comment 5

[Manuel Bucher [:manuel]]

No I can't reproduce. The window is always opened at the same location with the same size when setting both prefs (it doesn't restore the previous window size/position).

I'm not sure if the expected behavior with these prefs really is "The window should correctly restore its last position.". From what I can tell it seem like the expected behavior is "The window should start at the default location with the default size".

I do observe that the window is started in the maximized state and only then gets moved to the correct position and resized. But it is never off-screen for me.

The default window size has changed in Bug 1556002.

My Environment : Gnome 47, X11

Might be windows only bug (haven't tried to reproduce there) or might also be related to the screen resolution.

Comment 6

[sworddragon2]

For the case of reproduction: The system I'm on is a Windows 10 22H2 (64 bit) with all patches applied and the desktop resolution is 1680*1050. The Firefox window opens at the top left corner, either with around a positive margin of ~1 pixel (the mouse cursor always goes into window resize mode if I hover the very top or left) or with a negative margin of a few pixels on the next start of Firefox (it is good enough that I can still reach the top left buttons to maximize the window as usual).

Comment 7

[sworddragon2]

Edit: top right buttons, not left of course.

Comment 8

[sworddragon2]

Now that I have a few more minutes and on rereading the last posts:

(In reply to Manuel Bucher [:manuel] from comment #5)

No I can't reproduce. The window is always opened at the same location with the same size when setting both prefs (it doesn't restore the previous window size/position).

I'm not sure if the expected behavior with these prefs really is "The window should correctly restore its last position.". From what I can tell it seem like the expected behavior is "The window should start at the default location with the default size".

It might be worth mentioning that on previous versions the position was actually saved. But I don't remember if the window size (rounded on a stepping) was saved as well.

Comment 9

[Thorin [:thorin]]

may be relevant: Bug 1866583 edit: e.g. part [4/4] Ensure windows are not moved offscreen by `ConstrainPositionToBounds

Comment 10

[sworddragon2]

After updating Firefox to version 133.0.3 the issue is fixed. The window position keeps its position horizontally and vertically pixel-perfect even after multiple browser restarts and the position of the window is also saved again if I move it. The only thing that is not saved is the stepping size of the window. Even if I resize the window to be smaller it will resize to its original (now bigger) position after a browser restart. But then again I don't know if this was also the case before and if this is intended or not.

But since the window position is saved it probably would also make sense to save the window size as usual and round it to the next stepping - but this would be something for another ticket if somebody has interest into it.

Also there was a note on the changelog as well so this is probably a duplicate of bug #1934238 .

Edit: It seems I can't close this ticket as a duplicate since I lack pemissions for the other ticket.