1879790 - Firefox renders at old DPI settings when restarted (which makes the browser sort of unusable unless the user resizes the window )

Status: NEW

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

Description

[Mayank Bansal]

STR are somewhat long. Please see the attached video.

1. Use windows11. Monitor res = 1440p. Default DPI should be 150%
2. open browser
3. Open example.com in 2 tabs (tabA and tabB)
4. Drag out tabB to create a new window.
5. Use Windows snapping to snap tabB to the right. Then click on tabA such that it will snap to the left
6. Change windows DPI to 100% in windows settings
7. Switch back to the two browser windows. Drag-and-tabB to tabA such that there is only one browser window.
8. Close the browser
9. Change windows DPI to 150%
10. Open the browser

AR: The windows is vertically (and maybe horizontally) rendering at some large size. This means that the the title bar, menu bar, address bar are out of the users reach, unless the user horizontally resizes the browser. At this point, the browser will rerender at correct DPI settings.
If you resize the browser to rerender it correctly but dont maximize it, the browser will show the same behaviour on next start. Unless you resize-and-rerender the browser and then maximize it.

Comment 1

[Mayank Bansal]

Attachment: bandicam 2024-02-12 09-46-48-671.mp4

Comment 2

[Mayank Bansal]

Attachment: about:support

Comment 3

[Mayank Bansal]

1. Repros on a build fro, Jan2023, so not a recent regression.
2. This may also be a Windows bug (combination of DPI change and Windows Snapping).
3. This bug repros on all types of startup pages - Firefox Home, blank page, google.com etc. So this is not a bug of the Firefox Home

Comment 4

[Mayank Bansal]

Attachment: log.txt-main.6816.moz_log

about:logging for "Windows" preset, where I do the following STR:

1. Use windows11. Monitor res = 1440p. Default DPI should be 150%
2. open browser
3. Open example.com in 2 tabs (tabA and tabB)
4. Drag out tabB to create a new window.
5. Use Windows snapping to snap tabB to the right. Then click on tabA such that it will snap to the left
6. Change windows DPI to 100% in windows settings
7. Switch back to the two browser windows. Drag-and-tabB to tabA such that there is only one browser window.