Created attachment 1273468 [details] videofile showing a bug Description of problem: Intel HD 2500, Modesetting driver(i don t know about intel driver - it have tearfree option) When vertical synchronization is turned on in composite manager (Gnome, Kwin, Compton, etc.) strange artefacts appear when entering words in the address bar and having options for substitution. Both in Wayland and in Xorg there is a problem. Also in the torbrowser, which is based on firefox when playing video in full screen mode with fast motion as it were Interlaced video. I do not know if it's a video card driver or firefox issue, but I checked the Windows 7 radeon with no problem. If you disable vertical synchronization example in Gnome vblank_mode = 0 CLUTTER_VBLANK = none problem with the address bar disappears. Version-Release number of selected component (if applicable): Tested on 52-53 Firefox Fedora 25-26 Steps to Reproduce: Have an Intel graphics card. Turn on compositing. Installed Firefox. Enter the word in the address bar for which there are clues. Get black artifacts.
That report should me moved upstream at bugzilla.mozilla.org. If you mean the effect that black background windows is shown before URL bar options are rendered that's caused by default black background of dark themes. vblank causes that rendering of window content is delayed and background is shown.
Moving upstream: https://bugzilla.mozilla.org/show_bug.cgi?id=1339150