Affected versions

• 66.0b13
• 65.0.1
• 67.0a1

Affected platforms

• Windows 10x64
• Windows 7x64
• macOS 10.13

Steps to reproduce

1. Launch FF.
2. Go to about:preferences
3. Go to Language and Appearance
4. Under Fonts&Colors, select another font from the list.

Expected result

• The font should change each time the user is selecting a different font.

Actual result

• No changes are taking place when the user is changing the fonts from the list.

Regression range

• will return with a regression range ASAP.

Additional notes

• It can be noticed, that the only way the user can change the font from about:preferences is if he goes to Advanced settings and changes the Proportional value from Serif to Sans-Serif.

This is behaving as expected. The initial Firefox configuration is for the browser's default proportional font to be the CSS serif generic. The Default Font popup in Preferences is changing the font family used for serif.

However, the Wikipedia page shown in the screenshot isn't using serif, it uses sans-serif. Therefore, modifying the serif mapping has no effect.

Changing the default proportional font to sans-serif in the Advanced settings changes the behavior because this means the Default Font popup will now modify the mapping of sans-serif to an actual font family, and so it will affect the example Wikipedia page.

If you try a minimal test page such as

data:text/html,<h1>A Heading</h1><p>Some body text</p>

and then try changing the Default Font setting, you'll see that it works for either serif or sans-serif, whichever is the browser's default proportional font.

With an example like

data:text/html,<span style="font-family:serif">serif</span> and <span style="font-family:sans-serif">sans</span>

you can see the effect of the font preferences on content that explicitly uses either serif or sans-serif, as well as on content that uses whichever is currently the default proportional family.

AFAICS there's no Core bug here; the font prefs are working as expected.

I do believe the font-related options in Preferences are complex and confusing, and I suspect very few users ever understand how it is all meant to work; but that's primarily a front-end design problem. There are an awful lot of font.name.<generic>.<lang> preferences that can be set to customize defaults for various languages/scripts, and it's hard to come up with a simple yet flexible interface to expose them cleanly.

Moving this to Toolkit:Preferences, as I believe it's really a request for a redesign of this aspect of Preferences.

Yeah, in an ideal world we should rethink this. Aaron, who from UX could spend time looking at how to best present the user with font options? comment #1 is a good explanation of how things work today.