Open Bug 1717456 Opened 3 months ago Updated 2 months ago

Automatic change of "sizemode" from "maximized" to "normal" in xulstore.json


(Firefox :: Tabbed Browser, defect)

Firefox 89





(Reporter: lillsascha, Unassigned, NeedInfo)


(Whiteboard: QA-not-reproducible)

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:89.0) Gecko/20100101 Firefox/89.0

Steps to reproduce:

The problem occurs under Windows 10, whenever I change from another program (not Firefox) in "maximized" mode to Firefox, which I left in maximized mode.

Actual results:

The Firefox window automatically changes to "normal" mode (i.e., a resizable window). The xulstore.json adapts correspondingly.
The bug can be temporarily removed by deleting the xulstore.json file. However, it re-occurs as Firefox re-creates the xulstore file.
Denying Firefox writing access to the xulstore file doesn't work either, as another temporary version of the xulstore file is created.

Expected results:

Firefox should have stayed in "maximized" mode.

Hey Sascha,
I tried reproducing this issue on the latest versions of Firefox Nightly 91.0a1 (2021-06-21), beta 90.0b10 and release 89.0.1 but it stays maximized for me and doesn't change the state.

Can you test the issue while in Safe Mode? You can find helpful info here : .
Also a fresh new profile could help. You can find more about creating a new profile here : .
If possible, you can test this issue on the nightly build as well. Download the build from : .

Flags: needinfo?(lillsascha)
Whiteboard: QA-not-reproducible

Hi Andrei,

I tried the Safe Mode several times now. Interestingly, the bug goes away after starting Firefox in Safe Mode, but re-appears after some time.
The same happens if I switch back to the usual mode: it starts again and after some time, the bug appears.

I have not found any pattern in the re-appearance so far. Switching between a different program and Firefox several times does not reproduce the error - everything works fine, until at some randomly appearing point, the bug appears again, and does not go away until a restart of Firefox. This point is at some time between a few minutes and 1-2 hours. (probably, there is a trigger for the bug, but I couldn't find it yet)

The bug also appears in the Nightly version in the very same way: After a fresh restart, it cannot be reproduced. Only at some time, the bug starts to appear and persists, I.e. within any change from another program in a maximized window to Firefox in a previously maximized window, the Firefox window gets shrunk to "normal mode" with the size parameters written in the .xulstore file

Setting a component for this issue in order to get the dev team involved.
If you feel it's an incorrect one please feel free to change it to a more appropriate one.

Component: Untriaged → Tabbed Browser
You need to log in before you can comment on or make changes to this bug.