(In reply to Emilio Cobos Álvarez (:emilio) from comment #20) Non-composited X11 (the legacy variant of X11: i3, KDE with manually disabled compositor, etc.) does not support transparency. Everything that would usually be transparent/alpha is just black/opaque. Menus and window corners had [shadows on black background](https://bug1479135.bmoattachments.org/attachment.cgi?id=8995686) (=fat black borders). The autoscroll icon was a [black square with a white circle](https://bug1649246.bmoattachments.org/attachment.cgi?id=9160184) in it.
[XShapeCombineMask](https://searchfox.org/mozilla- central/search?q=XShapeCombineMask&path=) is implemented for software rendering only. Firefox creates a stencil (like a cookie cutter) of where transparency needs to get cut off. X11 then applies this stencil on every frame. The outer shadow of a rounded main menu, addon widget or [window titlebar](https://searchfox.org/mozilla- central/rev/37373cdeed20695af1ff1fd090f0736d9bf15e65/widget/gtk/nsWindow.cpp#6729,6793) has transparency, so it gets cut off by X11, leaving a rounded widget without shadow. XShapeCombineMask is not implemented for hardware rendering. That's why SW WR is enforced for menus, addons and autoscroll icon on non-composited X11 to make use of XShapeCombineMask while the main window is still using OpenGL. XShapeCombineMask * caused problems on [Mutter](https://searchfox.org/mozilla-central/rev/37373cdeed20695af1ff1fd090f0736d9bf15e65/widget/gtk/nsWindow.cpp#9084) back then * crashes the GPU process on Nvidia: bug 1730991 * causes performance problems according to the Chromium bugtracker: bug 1733094 comment 18,https://bugs.chromium.org/p/chromium/issues/detail?id=1198080 Could XShapeCombineMask be removed and instead menus and the autoscroll icon loose their border-radius (become rectangular) and loose their shadow (to avoid black background) if gdk_screen_is_composited() is false? IIUC, that would reduce code complexity, improve stability and performance. A rectangular autoscroll icon on non-composited X11 would be noticeable. But users choose non-composited X11 to get more performance than with composited X11. Considering this as well, it doesn't make sense to use XShapeCombineMask which contradicts their intent and causes above problems. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to firefox in Ubuntu. https://bugs.launchpad.net/bugs/1871644 Title: Top corners of Firefox windows have weird black protrusions from the rounded edges Status in Mozilla Firefox: Confirmed Status in firefox package in Ubuntu: Confirmed Bug description: Image to illustrate the problem is attached. All firefox windows on Wayland (EDIT: and X11) have a weird black protrusion from the top- left and top-right corners where yaru has curved the window corners, but something from Firefox appears to not be being clipped by the theme. I need to double check whether this appears on X11, but for now consider it Wayland only until I report back, although oSoMoN has checked their system and they don't see the behaviour (on X11). EDIT: I have now checked X11 on my system and I see the same behaviour as described above, so this is affecting BOTH Wayland AND X11 for me. ProblemType: Bug DistroRelease: Ubuntu 20.04 Package: firefox 75.0+build3-0ubuntu1 ProcVersionSignature: Ubuntu 5.4.0-21.25-generic 5.4.27 Uname: Linux 5.4.0-21-generic x86_64 NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair ApportVersion: 2.20.11-0ubuntu25 Architecture: amd64 BuildID: 20200403170909 CurrentDesktop: ubuntu:GNOME Date: Wed Apr 8 14:48:56 2020 InstallationDate: Installed on 2020-03-03 (35 days ago) InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Alpha amd64 (20200303) SourcePackage: firefox UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/firefox/+bug/1871644/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
