gnome-shell being busy messes up user I/O
Steps to reproduce
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Be in a Wayland session.
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Have a larger number of desktop icons (~100).
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Have a terminal open.
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Alternate between creating and deleting a file on the desktop, using the command line. Like
touch /home/user/desktop/bla # wait a few seconds rm /home/user/desktop/bla # wait a few seconds touch /home/user/desktop/bla # ...
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Move the mouse while doing so
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Hit Enter only once to send a command.
Current behavior
Hypothesis: gnome-shell being busy for some reason eats mouse movements and multiplies keystrokes.
Here another bug, which keeps gnome-shell busy for 2 or 3 seconds after creating or removing a desktop file, comes in handy. See the video attached below, each time a file gets created or removed, the screen freezes for these 2-3 seconds, then all desktop icons disappear, then they re-appear half a second later. This is not the bug I want to report here, though.
Symptom 1: moving the mouse to another place right after creating the file results in a frozen mouse pointer. Mouse becomes responsive again only after gnome-shell is no longer busy.
Symptom 2: Doing the same as in Symptom 1, but keeping the mouse in another place results in no mouse movement at all. Mouse pointer doesn't catch up with movements happening during the freeze. This also causes irregular mouse pointer behavior when gnome-shell is busy for shorter time spans in other situations.
Symptom 3: Even recording a screencast gets stuck when gnome-shell is busy. See the attached video, its frame sequence has noticeable time gaps.
Symptom 4: Hitting Enter for sending the command in the terminal apparently leads to 4-6 Enter keystrokes received by the application. See these multiple empty shell lines in the video, they're not result of multiple hits of the Enter key.
In an X11 session on the same hardware/installation, gnome-shell gets busy the same way (pause, icons vanishing for a moment), but mouse pointer stays responsive during the pause, no movements loss and also no keystroke multiplications.
Expected outcome
- Uninterrupted responsiveness of mouse movements.
- Uninterrupted responsiveness of screen display.
- Mouse pointer catching up after delays.
- No multiplied keystrokes.
Version information
This is Ubuntu 19.04 with all up to date packages as of 2019-08-08, booted into a Wayland session. CPU is a Core2Duo 2 GHz, graphics is a Radeon R7.
Additional information
Bildschirmvideo_von_09.08.2019_14_44_32.mkv
Note: VLC gets stuck at minute 0:05:600 in this video, Totem plays the video fine. These irregular video timestamps aren't result of a broken screencast recorder, but one of the bug symptoms. Playback in Totem matches about what one sees in reality.
This screencast was recorded with the built in screencast feature (shift-ctrl-alt-R), then cropped and equipped with frame numbers using Avidemux.