SUMMARY I'm running KDE Neon User Edition. After recent upgrade to Plasma 5.15.4 now every time I drag a window to the top edge of the screen to maximize it, the desktop *always* becomes unresponsive for exactly 13 seconds (I measured several times using my smartphone's clock). After that, the window usually maximizes normally. Now, for me, this bug persisted since I started using KDE Neon (which was around Plasma 5.12.*, I believe), *HOWEVER* until the recent upgrade (to 5.15.4) it the bug was occurring just occasionally. It worked without freezes most of the time, so I could live with that. Now the bug always persists, which kind of make system unusable for me (I'm looking into downgrade to 5.15.3 at least). STEPS TO REPRODUCE 1. Attempt to maximize any window by dragging it to the top edge of the screen (the option "Maximize windows by dragging them to the top edge of the screen" should be enabled in System Settings > Desktop behavior > Screen Edges) OBSERVED RESULT Desktop always becomes unresponsive for 13 seconds, after which window is maximized properly. EXPECTED RESULT Window maximized by dragging immediately. SOFTWARE/OS VERSIONS KDE Plasma Version: 5.15.4 KDE Frameworks Version: 5.56.0 Qt Version: 5.12.0 Kernel Version: 4.18.0-17-generic ADDITIONAL INFORMATION I have multi-monitor setup, but bug is reproducible even with one monitor disabled. Disabling Compositor has no effect. System Info: Machine: Device: laptop System: ASUSTeK product: X550VX v: 1.0 serial: N/A Mobo: ASUSTeK model: X550VX v: 1.0 serial: N/A UEFI [Legacy]: American Megatrends v: X550VX.302 date: 05/04/2017 Graphics: Card-1: Intel HD Graphics 530 bus-ID: 00:02.0 Card-2: NVIDIA GM107M [GeForce GTX 950M] bus-ID: 01:00.0 Display Server: x11 (X.Org 1.20.1 ) drivers: modesetting,nvidia (unloaded: fbdev,vesa,nouveau) Resolution: 1920x1080@59.97hz, 1920x1080@60.00hz OpenGL: renderer: GeForce GTX 950M/PCIe/SSE2 version: 4.6.0 NVIDIA 390.116 Direct Render: Yes Xrandr output: Screen 0: minimum 8 x 8, current 3840 x 1080, maximum 16384 x 16384 eDP-1-1 connected 1920x1080+1920+0 (normal left inverted right x axis y axis) 344mm x 193mm 1920x1080 60.00 + 59.97* 59.96 59.93 <...> HDMI-1-1 connected primary 1920x1080+0+0 (normal left inverted right x axis y axis) 598mm x 336mm 1920x1080 60.00*+ <...> DP-1-1 disconnected (normal left inverted right x axis y axis) XOrg log: X.Org X Server 1.20.1 X Protocol Version 11, Revision 0 [ 12.162] Build Operating System: Linux 4.4.0-140-generic x86_64 Ubuntu [ 12.162] Current Operating System: Linux comper-shbook 4.18.0-17-generic #18~18.04.1-Ubuntu SMP Fri Mar 15 15:27:12 UTC 2019 x 86_64 [ 12.162] Kernel command line: BOOT_IMAGE=/@/boot/vmlinuz-4.18.0-17-generic root=UUID=ac53502d-8d17-4d77-965c-30cf1c4754af ro r ootflags=subvol=@ quiet splash vt.handoff=1 [ 12.162] Build Date: 27 November 2018 05:27:12PM [ 12.162] xorg-server-hwe-18.04 2:1.20.1-3ubuntu2.1~18.04.1 (For technical support please see http://www.ubuntu.com/support) [ 12.162] Current version of pixman: 0.34.0 <...> [ 12.163] (==) Using system config directory "/usr/share/X11/xorg.conf.d" [ 12.185] (==) No Layout section. Using the first Screen section. [ 12.185] (==) No screen section available. Using defaults. [ 12.185] (**) |-->Screen "Default Screen Section" (0) [ 12.185] (**) | |-->Monitor "<default monitor>" [ 12.185] (==) No monitor specified for screen "Default Screen Section". Using a default monitor configuration. [ 12.185] (==) Automatically adding devices [ 12.185] (==) Automatically enabling devices [ 12.185] (==) Automatically adding GPU devices [ 12.185] (==) Automatically binding GPU devices [ 12.185] (==) Max clients allowed: 256, resource mask: 0x1fffff [ 12.186] (WW) The directory "/usr/share/fonts/X11/cyrillic" does not exist. [ 12.186] Entry deleted from font path. [ 12.186] (WW) The directory "/usr/share/fonts/X11/100dpi/" does not exist. [ 12.186] Entry deleted from font path. [ 12.186] (WW) The directory "/usr/share/fonts/X11/75dpi/" does not exist. [ 12.187] Entry deleted from font path. [ 12.187] (WW) The directory "/usr/share/fonts/X11/100dpi" does not exist. [ 12.187] Entry deleted from font path. [ 12.187] (WW) The directory "/usr/share/fonts/X11/75dpi" does not exist. [ 12.187] Entry deleted from font path. [ 12.187] (==) FontPath set to: /usr/share/fonts/X11/misc, /usr/share/fonts/X11/Type1, built-ins [ 12.187] (==) ModulePath set to "/usr/lib/xorg/modules" [ 12.187] (II) The server relies on udev to provide the list of input devices. If no devices become available, reconfigure udev or disable AutoAddDevices. [ 12.187] (II) Loader magic: 0x5627e36b2020 [ 12.187] (II) Module ABI versions: [ 12.187] X.Org ANSI C Emulation: 0.4 [ 12.187] X.Org Video Driver: 24.0 [ 12.187] X.Org XInput driver : 24.1 [ 12.187] X.Org Server Extension : 10.0 [ 12.187] (++) using VT number 1
UPDATE: Attempt drag windows to left/right screen edge reproduces the bug as well. It seems like the freeze occurs whenever the animation of future window size filling the space tries to play (it plays eventually, after the freeze). Note that maximizing animation itself works flawlessly, and I can maximize windows via "maximize" button or by double-clicking their headers without delays.
UPDATE #2: The problem doesn't occur in Wayland sessions. So, after a lot of experimentation with video drivers and Xorg configuration I was able to fix this issue. That involved switching back and forth between Nvidia and Nouveau drivers via the Driver Manager (Ubuntu's version). I'm still not sure how exactly it was fixed, but the one notable difference is that modesetting driver is not loaded as seen in "inxi" output: Graphics: Card-1: Intel HD Graphics 530 bus-ID: 00:02.0 Card-2: NVIDIA GM107M [GeForce GTX 950M] bus-ID: 01:00.0 Display Server: X.Org 1.20.1 drivers: nvidia (unloaded: modesetting,nouveau) Resolution: 1360x768@59.96hz, 1920x1080@60.00hz OpenGL: renderer: GeForce GTX 950M/PCIe/SSE2 version: 4.6.0 NVIDIA 390.116 Direct Render: Yes
*** This bug has been marked as a duplicate of bug 406319 ***