Comment 51 for bug 1500282

(In reply to Karl Tomlinson (:karlt) from comment #11)
> (In reply to Stefan Seidel from comment #8)
> > So is there a reason to apply the rounding *in Firefox* where my patch would
> > remove it? From a GTK3 point of view, probably, because the reason you
> > mentioned that an application can provide hi-res bitmaps etc. From a Firefox
> > point of view, I can say that there is no *technical* reason, i.e. setting
> > devPixelsPerPx to a float value by hand (as Kai Mast has reported), produces
> > the desired result - Firefox scales the content according to the preference.
>
> There are similar reasons re images from web content.
> Firefox will scale, but will only render without interpolation if the web
> content supports the resolution.
>
> See also https://bugzilla.mozilla.org/show_bug.cgi?id=1081142#c10
>
> > Comparing this
> > to the Windows behaviour: the set scaling it read from the system as is,
> > with no rounding applied.
>
> Windows usually scales in steps, 1, 1.25, 1.5, 2 (and maybe higher).
>
> Adding a 1.5 step makes sense, I think, especially because this is supported
> on Windows, and so has some chance of support from web authors.
>
> I'm not so keen on adding 1.25 because the benefits of a different size don't
> necessarily outweigh the disadvantage of likely interpolation. At 1.25,
> Windows defaults (in some versions at least) to XP scaling, which scales
> font sizes but not pixels. Doing this in web content broke too many sites.
> The goal is to pick what will be best for most and layout.css.devPixelsPerPx
> is available for those where this doesn't work out.

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