(In reply to Philipp Sackl [:phlsa] please use needinfo from bug 1173725 comment #95) > There's still the issue that the top border is slightly thinner when running > at 200%, but I'll file a follow-up for that. This is the followup.

Yeah, window border should be 2 physical pixels all the way around, but it's only 1 pixel on top at 200% for me too.

Trivial fix. I assume we don't need to worry about scaling factors < 1.0? Needed to move RoundDown earlier so I could use it, didn't seem to be an obviously good spot for it, better suggestions welcome.

Comment on attachment 8636411 [details] [diff] [review] Patch v.1 looks good to me.

url: https://hg.mozilla.org/integration/fx-team/rev/f04abbcad33ab553482f5d766fb1e92d58aeac3a changeset: f04abbcad33ab553482f5d766fb1e92d58aeac3a user: Justin Dolske <dolske@mozilla.com> date: Tue Jul 21 11:24:16 2015 -0700 description: Bug 1184942 - Use DPI scaling factor to ensure top window border is correct thickness. r=jimm

Comment on attachment 8636411 [details] [diff] [review] Patch v.1 Approval Request Comment [Feature/regressing bug #]: Windows 10 theme [User impact if declined]: window border looks wrong at some scale factors [Describe test coverage new/current, TreeHerder]: n/a [Risks and why]: low, trivial patch and win10 only. [String/UUID change made/needed]: n/a

Comment on attachment 8636411 [details] [diff] [review] Patch v.1 Small change that is isolated to Windows 10. Beta+ Aurora+

Verified on Windows 10 64-bit using: *latest 42.0a1 Nightly, build ID: 20150810030205, *latest 41.0a2 Aurora, build ID: 20150810004008, *Firefox 40 RC, build ID: 20150807085045.