Konqueror's Terminal Emulator sometimes doesn't display command output #482
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opened 3 weeks ago by AlexKent
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Basic information
Description
When using the "Terminal Emulator" in Konqueror to run a command then the command's output is sometimes (but not always) not output until the Enter key is pressed an additional time or window focus is changed (i.e. focusing a different window). Pressing Control+c appears to temporarily fix the issue. I have not seen this behaviour in the stand-alone Konsole application. This issue did not appear until recently (within the past year or so) and may be due to different system libraries (problem started some time after a system upgrade).
Steps to reproduce
The exact circumstances that trigger the bug are unknown. Sometimes the bug is present only to go away for no apparent reason later in the same session (and in the same Terminal Emulator instance). The following might make it occur:
/tmp/).F8).rm -rI nonexistent_directory/then press the Enter key.rm: remove 1 argument recursively?but when the bug is occurring then nothing is displayed (the cursor remains at the end of thermcommand line).Sorry for being so vague.
Are you able to take some screenshots the next time this happens? I can't reproduce it here, I tried a few times.
Note: I think I've tracked down the bug and come up with a fix. There is no good way to reproduce this issue on demand on a stock install but I think I know a simple patch that can be applied that will (when requested) simulate the problematic conditions and trigger the issue. All this will be detailed in a later comment once I've had a chance to test my hypotheses. The comments below are included for documentation purposes.
Additional info
It just started happening again (it's frustratingly-intermittent).
I tried to take a screenshot but doing so caused the stalled output to display. I did get some photos with my phone though.
When the bug is occurring there is partial scrolling and then an 8 to 15 second pause before the scroll is completed and all output is shown correctly.
Attached are photos of the bug in action (annotated and with personal info redacted). The colored bars in the first two images show the lines that have (blue) and have not (magenta) been scrolled when the bug is occurring.
1 before.png→ State of terminal before pressing Enter1 during bug.png→ State of terminal while stalled after pressing Enter2 during bug.png→ State of terminal while stalled2 after timeout.png→ State of terminal after a few seconds@AlexKent thanks for the pics. As per our discussion on IRC, have you been able to verify if this happens only when Compton is enabled?
If you have a patch, that is great. Prepare a PR when you are ready to release it.