Public bug reported:
Ubuntu 18.04. Gnome X11 session.
When window focus policy is set to follow the mouse, then if the mouse
is moved into a new window and keystrokes typed immediately afterwards,
the keystrokes go to the old window (invariably causing application
errors).
This is extremely annoying for rapid-fire developers, who for example
run vim in one window to edit a script and bash in another to test the
script; the sequence 1) save changes in vim; 2) move mouse to the bash
window; 3) type the command to run the script results in the shell
command (or part of it) being received by vim in the old window (with
occasionally-entertaining effects).
It seems like mouse-movement events are not kept in-order with respect
to keyboard events. I can see the mouse pointer move to the new window
before I type on the keyboard, so I know the mouse-move events have been
received before the keystrokes.
Speculations:
This might be a window-manager bug: Although the mouse cursor has moved
before I type, the window borders may not yet have changed to indicate a
changed focus (not certain because the sequence is so quick). Therefore
the window manager might be (erroneously) continuing to pass keystrokes
to the "current" (i.e. old) window after the mouse moves into the new
window. I'm assuming here that the window manager is able to receive
mouse-move and keyboard events in a single stream, or timestamped, or
otherwise marked so they can be processed in the order they originally
occurred.
Or maybe Xorg does not keep them in order or doesn't allow the window-
manager to know their relative order. Or maybe keystrokes are going
directly to the old window without filtering for the current mouse
position (if this is the case, then IMO xorg should be told to stop
delivering keystrokes if the mouse is outside a specified region until
the window-manager tells it to resume delivery; or some similar way to
allow the focus-change to occur first).
STEPS TO REPRODUCE:
1. Run gnome-tweaks, set Windows->Window Focus to "Sloppy"
2. Open two vertically-adjacent gnome-terminal windows
3. Put cursor in the top window. Wait 2 seconds.
4. Move mouse (with one hand) rapidly into the other window, then (immediately)
type a character into the other window (with the other hand)
ACTUAL RESULTS: The keystroke appears in the old window
EXPECTED RESULTS: Keystroke appears in the new window (i.e. the
keystroke is not processed at all until the window manager completes the
focus change). In other words, "typeahead" should encompass both
keystrokes and mouse movements.
** Affects: xorg (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/1814839
Title:
keystrokes go to wrong window immediately after moving mouse to change
window focus
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