Created attachment 120808 [details] Slow QMessageBox in Kwrite SUMMARY QMessageBox is slow for the first pop-up. For example, the message box asking for confirmation to empty trash, the message box asking to close KWrite when there are unsaved changes. Note that if I cancel and try to trigger the message box again shortly, it's not slow the second time. STEPS TO REPRODUCE For KWrite: 1. Freshly Launch KWrite 2. Type something in. 3. Close KWrite. The popup message box is slow. For Trash: 1. Restart computer with something in Trash. 2. Try to Empty Trash. Confirmatory message box is slow. OBSERVED RESULT My computer seems to stop responding for a while during the launch of QMessageBox (for example, sound pauses). Screenshot Attached. EXPECTED RESULT QMessageBox launches at normal speed. SOFTWARE/OS VERSIONS Linux/KDE Plasma: KDE Neon (Ubuntu 18.04) (available in About System) KDE Plasma Version: 5.16.0 KDE Frameworks Version: 5.59.0 Qt Version: 5.12.3 ADDITIONAL INFORMATION I noticed this issue after a recent (KDE Neon) update.
Edit: This issue appears to have been fixed by updates today.
Sorry for reopening, but the issue came back for me again. I think I found out the cause -- it was the audio that played with the warning dialog. I changed a line in "/etc/pulse/daemon.conf" from "; default-fragment-size-msec = 25" to "; default-fragment-;size-msec = 2", and now there's no lag with the warning dialog. I'm not sure what it does or how it was set to 25 but reopened the issue just in case it was a bad default.
If you changed it without removing the semicolon, then you effectively changed nothing. The semicolon denotes a comment, comments do nothing. What's more: I am unable to reproduce this on a pristine/new installation. I think you may be on the right track with suspecting pulseaudio as the culprit, but seeing as this isn't reproducible on a stock installation I am not sure how we can debug let alone fix this.
You're right -- I didn't debug it correctly last night. (I was logging in and out after changing settings) After debugging today, I think I found the issue -- the lag only occurs for me with HDMI/DisplayPort 2 (GP104) output. I switched to built-in Analog and there was no lag. The issue is probably with the drivers, and not plasma. (My setup was graphics card -> display port -> monitor -> audio jack -> speakers.) Thank you for your help. Here are details of how I debugged the issue: First, I uninstalled pulseaudio and the lag went away (along with audio). I reinstalled pulseaudio and plasma-pa. The sound initially didn't work, but there was no lag. I changed the output to HDMI/DP2 GP104 and the sound came on, with the lag for warning dialog. I tried changing output to built-in Analog and plugged something else in, and I got the sound with no lag. I restarted a few times testing this.