User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0 Build ID: 20170810100255 Steps to reproduce: 1. Navigate to http://www.popuptest.com/goodpopups.html and click on a Good PopUp #1 link 2. Maximize pop-up window Actual results: See Caption buttons as not positioned correctly. Expected results: Caption buttons are following default Windows behaviour. See attachment. I think this is a long term bug.

(In reply to Eddward from comment #0) > Caption buttons are following default Windows behaviour. > See attachment. > I think this is a long term bug. Can you explain what you mean by this?

Not sure what exactly you need to explain. 1. Expected behavior is that the buttons will be positioned correctly as in the other maximized win32 windows. 2. Long term bug because is not present only in the Nightly, but also in every Firefox since version 50 at least.

(In reply to Eddward from comment #2) > 2. Long term bug because is not present only in the Nightly, but also in > every Firefox since version 50 at least. Were there versions that didn't have this bug?

I don't have an answer on this. Is possible that there aren't, but it is a minor, but still (in my opinion)a valid bug.

It seems to be Windows 10 regression only, or at least there is no such problem on Windows 7 Aero or Classic theme. Verified with Firefox 52. Basically, I think the root cause is that caption buttons on Windows 10 have different shape in windowed mode and different in maximized mode and Firefox is painting pop-up caption buttons in both modes in the same shape.

Is this improved on today's nightly after bug 1375335?

Checking on 57.0a1 (2017-08-14) (64-bit). Still the same, so unfortunately no.

(In reply to Eddward from comment #7) > Checking on 57.0a1 (2017-08-14) (64-bit). Still the same, so unfortunately > no. That's yesterday's nightly, it wouldn't have the fix from bug 1375335. Today's will, but might not be available yet.

Ok tested on latest mozilla-central build. Built from https://hg.mozilla.org/mozilla-central/rev/564e82f0f289af976da01c2d50507017bbc152b5 And still the same. No change.

Actually this is also affecting the main Firefox window in maximized state with Titlebar enabled. See new attachment.

Verified as fixed on Windows 10 x64 Fx 57.0b14 and 58.0a1.