Created attachment 148245 [details] video showing the bug Pop-up windows in both Firefox and Thunderbird will often appear empty. This can most easily be reproduced by selecting Help -> About Firefox/Thunderbird from each application's hamburger menu (see attached video). You may have to try this a few times to get the failure. This bug started happening after a recent KDE stuff update and is reproducible on both of my computers running KDE neon, detailed below. I have not, however, been able to reproduce the issue within VirtualBox. Once a window appears blank, it will remain so until the window is minimized/restored, or in cases where the window features a button or other interactive widget, moving the cursor over the widget can cause the window to be properly drawn. Switching to the "Plastik" decoration solves the issue. Adjusting various settings within the Breeze window decoration (borders, shadow, gradient, etc.) had no effect. Also, this does not appear to be a compositing issue, as the bug persists with compositing disabled.
Whoops, I accidentally submitted the bug before I had finished writing. Here is my system info: System #1: * OS: KDE Neon 5.24 User Edition (Plasma Desktop 5.24.4, KDE Frameworks 5.93.0, Qt 5.15.3) * Linux Kernel: 5.15.34-xanmod1 (64-bit) * Motherboard: ASRock X58 Extreme3 (Intel X58 chipset) * CPU: Intel Core i7-990x Gulftown (3.46 GHz hexa-core, Socket 1366) @ 4.15 GHz * RAM: 24GB (6x G.Skill 4GB DDR3 PC3-10666 1333 MHz) @ 1430 MHz * Video: EVGA NVIDIA GeForce GTX 980 Ti SC GAMING ACX 2.0+ w/ 6GB RAM * NVIDIA video driver:** 470.103.01 System #2: * OS: KDE Neon 5.24 User Edition (Plasma Desktop 5.24.4, KDE Frameworks 5.93.0, Qt 5.15.3) * Linux Kernel: 5.10.111-xanmod1 * PC: HP Pavilion m6-1035dx * CPU/GPU: AMD A10-4600M 2.3 GHz quad-core APU with Trinity [Radeon HD 7660G] Graphics (using xorg radeon driver) * RAM: 8GB DDR3 (2x 4GB PC3-12800 1600 MHz) * Xorg radeon driver: "Northern Islands", specifically ARUBA (Trinity/Richland) * Xorg radeon 3D driver: r600g
Cannot reproduce on Wayland with Firefox 99.0.1 or Thunderbird 91.8.0. Can you try on Wayland and see if the issue persists for you there?
Created attachment 148249 [details] how the bug looks on Wayland I can also get the bug to happen on Wayland, but instead of a blank, seemingly transparent window, it's just black (see attached screenshot).
Thanks. Could be a KWin issue, or an issue in those apps.
(In reply to Nate Graham from comment #4) > Thanks. Could be a KWin issue, or an issue in those apps. I suspect KWin since it happens with Breeze but not the Plastik decoration.
I've tested this more thoroughly tonight and discovered I can repro the bug using the latest neon and Manjaro liveCD images. However, I am now less convinced this is explicitly a kwin issue and more likely a timing issue caused perhaps by the Mozilla apps creating a window and then being late with its contents. The bug only appears when the timing is just right, and that timing can be impacted by the window decoration chosen, the host system's specs, and whether or not one's cat is in heat. Further observations from my testing include: * The snap version of Firefox is not affected by this bug * The Gnome window manager does not exhibit the bug. * The XFCE window manager *does* exhibit the bug. * Kwin exhibits the bug when using the Breeze window decoration, but not Plastik. * I cannot repro the bug in VirtualBox, only on real hardware. * It can take several attempts to get the bug to appear, particularly in Thunderbird. I can repro the bug back as early as the Kubuntu 21.10 LiveCD (Plasma 5.22.5, Frameworks 5.86.0, Qt 5.15.2, Firefox 93.0.0), but not Kubuntu 21.04 (Plasma 5.21.4, Frameworks 5.80.0, Qt 5.15.2, Firefox 87.0), though I acknowledge not much can be inferred from this.
That does seem likely. I can reproduce a flash when the window is opened. It seems like the content does indeed arrive late. Can you report this downstream to the Mozilla folks? Thanks!