Created attachment 145244 [details]
screencast

SUMMARY

Overview of directory with many pictures does not repaint on return from full view of single picture, if the selection is off the center row. Moving the mouse within triggers the icons to be repainted one by one. Moving the mouse out and over the sidebar repaints the whole component.

STEPS TO REPRODUCE
1. open information or folder sidebar
2. open folder with e.g. 100 pictures
3. increase size of preview icon, to show only a few per line
4. scroll down to the middle, so the scroll-pane won't bump into the upper or lower end
5. click on any picture to show it fullsize, that is not in the center row - will also place the selection on this icon
6. press ESC on the keyboard and move the mouse around

OBSERVED RESULT

The selected image shall move to the center row and thereby trigger a scroll. But the repaint is missing. The moving mouse will only repaint piecewise until the mouse moves out of the overview component to trigger a full repaint.
See attached screencast.

EXPECTED RESULT

The repaint shall leave a consistent state, that does not cause confusion by "uncovering" the real position of icons piecewise.

SOFTWARE/OS VERSIONS

Betriebssystem: Kubuntu 21.10
KDE-Plasma-Version: 5.22.5
KDE-Frameworks-Version: 5.86.0
Qt-Version: 5.15.2
Kernel-Version: 5.13.0-22-generic (64-bit)
Grafik-Plattform: X11
Prozessoren: 8 × Intel® Core™ i7-4700MQ CPU @ 2.40GHz
Speicher: 15,5 GiB Arbeitsspeicher
Grafikprozessor: Mesa DRI Intel® HD Graphics 4600

ADDITIONAL INFORMATION

The steps to reproduce are not totally reliable. If repeatedly clicking the same two images first one row above the center and second one row below the center it might "heal" the error - seemingly some "offscreen-buffer" from before can be reused and all of a sudden it works as expected.

Also changing to different directories - especially those with fewer images to not allow scrolling - might "fix" the error.

If the Window-hight interacts badly with the icon-size, clicking images close to the last row might cause scroll-increments of less than a full icon-hight. "Uncovering" them with the mouse one-by-one "violates" the grid position and causes "half-high" cells