1335812 - Incorrect scaling of dialogs when using a HiDPI monitor and a standard monitor on Windows

Status: NEW

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

Description

[Tyson Smith [:tsmith]]

Attachment: bad_about_size.png

On my current setup I have two monitors a 27" 4K (3840x2160) monitor and a 24" (1920x1200) and I am running Windows 10 (1607)

The 4K monitor is scaled to 175% (otherwise everything would be tiny) and the standard monitor is at 100%.

When the browser is on the standard display some dialogs are scaled incorrectly (see attached images)

Comment 1

[Tyson Smith [:tsmith]]

Attachment: bad_dialog_size.png

Comment 2

[Tyson Smith [:tsmith]]

Attachment: current_setup.png

Comment 3

[Skye]

I've got the same problem; it's always worked fine up until now so this appears to be a regression introduced with the most recent 52.0b3 update.

Comment 4

[Tracy Walker [:tracy]]

Hi Tyson, please check out bug 1239347.  I'm curious, is what you're experiencing the same as described there?

Comment 5

[Tyson Smith [:tsmith]]

(In reply to Tracy Walker [:tracy] from comment #4)
> Hi Tyson, please check out bug 1239347.  I'm curious, is what you're
> experiencing the same as described there?

No that seems to be slightly different. I think.

Comment 6

[Mystral77]

Version : 59.0.2 (X64)
OS : Windows 10 (1709 build)
Main screen : laptop 17" 3840x2160 - 175% scale
Second screen : HD monitor 23" 1920x1080 - 100% scale

Same problem with version 59.0.2 (X64)

I have a laptop with 4K screen configured to 175% scale and a standard HD monitor configured to 100% scale.
Firefox on the 4K screen is good, but if I put it in the second monitor, the scale is not ok : too too big to be used.
Chrome, Opera, Maxthon or Edge can resize the UI with the new DPI settings on the second monitor, but not Firefox.

An extension made the job but only for version prior than V57 : https://github.com/ertug/autohidpi

Thank you...

Comment 7

[Mystral77]

Attachment: Firefox 59 on 4K monitor

Comment 8

[Mystral77]

Attachment: hdmonitor.png

Same Firefox as 4kmonitor dragged to the HD monitor

Comment 9

[Raluca Popovici, Desktop QA]

I can reproduce this issue on my machine on Fx 86.0a1(2021-01-22) , win 10x64 with 2x external displays: a 4K (3840x2160) - scale 175% and a 1920x1080 - scale 100%.

Comment 10

[Jim Mathies [:jimm]]

Two issues here -

1. rescaling issues when dragging between two monitors scaled differently
2. a few Firefox dialogs scaled incorrectly on one of the monitors with mixed scaling

Comment 11

[Jim Mathies [:jimm]]

• issue with propagating scale changes down to content. widget, ipc, content process
• issues with windows that are split between two screens
• start investigating on Windows
• code exists to handle this, but there may be bugs

Matt, could you take a look?

Comment 12

[Jeff Muizelaar [:jrmuizel]]

We try to handle WM_DPICHANGED here:
https://searchfox.org/mozilla-central/rev/927e525f481a93a8f63d27a78ae6201e42b1b1fb/widget/windows/nsWindow.cpp#6181

Perhaps something is going wrong.

Comment 13

[Jim Mathies [:jimm]]

FWIW, I was not able to reproduce this issue using two monitors with 150% scaling (primary) and 100% scaling. I tested with file open, file save, the about dialog, and various right-click context menus. Moving firefox (completely) from one monitor to the other resulted in UI that appeared to be scaled correctly.

Comment 14

[Matt Woodrow (:mattwoodrow)]

(In reply to Raluca from comment #9)

I can reproduce this issue on my machine on Fx 86.0a1(2021-01-22) , win 10x64 with 2x external displays: a 4K (3840x2160) - scale 175% and a 1920x1080 - scale 100%.

Which behaviour did you reproduce, and what were the STR for that? Thanks!

Comment 15

[Raluca Popovici, Desktop QA]

1. rescaling issues when dragging between two monitors scaled differently. Please see the following video:
   https://imgur.com/a/XYXwSYC
2. a few Firefox dialogs scaled incorrectly on one of the monitors with mixed scaling. Please see the 2 screenshots attached:

• 4k monitor 3840x2160 scale 175% : https://imgur.com/a/Bh8X5dT
• Standard 1920x1080 scale 100%: https://imgur.com/a/taFItkM