Comment 32 for bug 1500282

(In reply to Stefan Seidel from comment #12)
> As for GTK3 - I don't actually have a fully fledged GNOME system to test
> with, but can one set arbitrary values in the "normal user" control panel
> for the DPI/font scaling or does it have steps?

Xft.dpi is equivalent to GNOME's text scaling factor, which accepts floating
point values. Unit scaling is 96.0.

The GDK_SCALE environment variable is equivalent to the pixel scaling factor,
which affects everything (not just text). It is constrained to integer
values.

I don't know what exactly is presented in GNOME's UI. Other DE's may vary.

> In any case, are we not in the same situation as in Windows, where the
> system deliveres a DPI value (however rounded/stepped it may be from the
> OS's point of view) and Firefox just uses this value to determine the
> defaultScale?

We are in a situation where we have one scaling factor that is similar to Mac
(GDK_SCALE) and the other is similar to NT, but on nix has not been used to
scale more than text in native apps. I hear some special apps (Libreoffice,
Chrome, Firefox) have used the text scaling factor for more than text.

(In reply to Stefan Seidel from comment #13)
> At the risk of overengineering this, would it be possible to set a special
> value (like -2.0) to apply the correct system scaling at the expense of
> blurriness? I can see from this and the other bug's comments that clearly
> there are users out there who prefer correct scaling over "beautiful"
> scaling. And certainly for DPI values around 1.5×96 DPI, which is _very_
> common, the steps 1x and 2x are really too coarse, even 1.5x might not be
> enough. Also, I think the common use case is that GNOME sets the scaling
> correctly to an integer value, and only if the user is not satisfied with
> the look — or, for example, sight-impaired — the user will set the scaling
> to a different value.

I can see that some might like to use the text scale factor for the pixel
scaling factor. I'm happy for such an option to be added, but I don't think
it should be the default.

> I think if a user sets an explicit value for the system font size (and all
> application will obey), Firefox should follow this setting too.

Firefox should be using the system font sizes for system fonts. It is a bug
if it is not.

Author-specified sizes in web content are another issue and problematic
because CSS requires that the same scale factor be used for text and pixels.