Created attachment 150987 [details]
broken panel visibility during desktopgrid animation

SUMMARY

Since bug 451590 got fixed now (WindowHeap animation stuttering), it's become more obvious that there's an issue with desktop panels when opening and closing the desktop-grid.

1. Panels set to auto-hide are incorrectly fading in while closing the grid and they disappear instantly when the animation finishes (this can only be observed when no window is maximized). This is the bigger issue of the two, as it makes the closing animation appear glitchy.

2. Panels which are are always visible don't fade out while opening the desktop grid. Compared to when closing the grid, the panels correctly fade in. This is just a minor inconsistency issue.

STEPS TO REPRODUCE

Set the global animation scaling factor to a slow value to properly see the issue.

1.1. Have a panel added to the desktop and set to auto-hide
1.2. Open desktop grid and close it again on a desktop where no window is maximized
1.3. Watch the panel incorrectly fade in when closing the grid, even though it's supposed to stay hidden, and then watch it disappear instantly when the animation finishes

2.1. Have a panel added to the desktop and set to always-visible
2.2. Open desktop grid and close it again on a desktop where no window is maximized
2.3. Watch the panel disappear immediately when opening the grid, and watch it correctly fade in when closing the grid

SOFTWARE/OS VERSIONS

kwin built from latest commit on the Plasma/5.25 branch (9d7b7ad08102)