932638 - Firefox ignores Windows compatibility option "Disable scaling on high DPI settings"

Status: UNCONFIRMED

(Core :: Graphics, defect)

Description

[Terrell Kelley]

User Agent: Mozilla/5.0 (Windows NT 6.1; rv:24.0) Gecko/20100101 Firefox/24.0 (Beta/Release)
Build ID: 20130915200815

Steps to reproduce:

I'm filing this on 27 because it's still present in Nightly, but I found this bug is present as far back as Firefox 22.

Right-click on the Firefox shortcut and choose Properties. Click the Compatibility tab and check  "Disable scaling on high DPI settings," and click OK.


Actual results:

Firefox continued to use the system DPI setting. (120dpi in my case)


Expected results:

Firefox should revert to the default 96dpi.


Extra Information:

In Firefox 24, this can be worked around by setting layout.css.dpi to 1. However, this setting does not work on Firefox 27 (see bug 932634).

Comment 1

[Alex]

http://blogs.msdn.com/b/patricka/archive/2010/04/15/why-does-a-high-dpi-setting-make-my-application-look-fuzzy-and-have-clipped-text.aspx

That option is meant for compatibility with old applications that don't mark themselves as aware of DPI scaling (Firefox does), it shouldn't have any affect on an app like Firefox.

Comment 2

[Terrell Kelley]

(In reply to Alex from comment #1)
> http://blogs.msdn.com/b/patricka/archive/2010/04/15/why-does-a-high-dpi-
> setting-make-my-application-look-fuzzy-and-have-clipped-text.aspx
> 
> That option is meant for compatibility with old applications that don't mark
> themselves as aware of DPI scaling (Firefox does), it shouldn't have any
> affect on an app like Firefox.

Your link does not say that at all. There is nothing in that link saying that DPI aware applications should ignore the setting. I don't know where in the world you got that idea. 

Literally every other application I have ever used honors the setting. It is the expected behavior on the Windows platform. The very link you gave specifically says that the option is supposed to do something.

Furthermore, it's not like Firefox ignores any other compatibility setting. Windows XP compatibility still disabled Aero. Disabling the DWM still works in Windows 7. Disabling themes still works. Why should Firefox get to pick and choose which compatibility settings it implements?

Comment 3

[Terrell Kelley]

And, let's not forget, Firefox's DPI scaling implementation is very bare bones. It still looks like an application that does not do its own DPI scaling. The icons are still fuzzy. The default zoom makes page images fuzzy.

To the user, it looks like the same Vista-style scaling that Windows does. So, if they want crisp images, they expect to be able to fix this using the compatibility options. If we are going to do our own scaling, we need to make sure we handle all use cases.

A user who has this compatibility option checked at the very least expects to not have fuzzy images. This is part of the reason there was such an outrage when this was implemented. (The other was not implementing XP-style chrome font-only scaling--which is what most people actually used. But that's another bug.)