User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:58.0) Gecko/20100101 Firefox/58.0 Build ID: 20170929100122 Steps to reproduce: After today's update I was using the "Mightly" lightweight theme. When I restarted, the window did not show up. After getting back to a usable state, I went to Add-ons -> Themes, and enabled some of my other lightweight themes. I have found that some themes turn the window frame white, and those themes will render the invisible window on Nightly restart. Some of those themes: https://addons.mozilla.org/en-US/firefox/addon/abstracblue/ https://addons.mozilla.org/en-US/firefox/addon/aurora-australis/ https://addons.mozilla.org/en-US/firefox/addon/blue-bomb/ https://addons.mozilla.org/en-US/firefox/addon/frozen-wood/ https://addons.mozilla.org/en-US/firefox/addon/nightly/ I am using build ID 20170929100122 Actual results: Certain lightweight themes caused the window frame to be white when switching themes from the add-on manager. If one of those themes is enabled and the browser is closed and restarted, the window is invisible on restart. Expected results: The theme should be applied without a white border and the browser window should not be invisible.

The problem here is that these lightweight themes set invalid color values as the accent color. E.g. the abstracblue theme seems to use "#None", which ends up getting resolved to transparent.

Comment on attachment 8913758 [details] Bug 1404386 - Sanitize theme accentcolor to prevent the window from becoming transparent. https://reviewboard.mozilla.org/r/185150/#review190180 LGTM. Can we add an automated test for this?

(In reply to :Gijs from comment #3) > Comment on attachment 8913758 [details] > Bug 1404386 - Sanitize theme accentcolor to prevent the window from becoming > transparent. > > https://reviewboard.mozilla.org/r/185150/#review190180 > > LGTM. Can we add an automated test for this? I'll look into it later.

Pushed by dgottwald@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/1a6703bd1904 Sanitize theme accentcolor to prevent the window from becoming transparent. r=Gijs

Confirming as fixed. Thanks!

Verified issue as fixed on 57.0b9 20171016185129 with Windows 10x64.