Created attachment 143229 [details]
Drag&drop, dolphin, single file

SUMMARY
When dragging a single file in Dolphin (details mode), both the icon and text seems rendered in low resolution, with jagged edges. (attachment1 [details])
When dragging multiple files, the icons look better, but still not as smooth as the original. (attachment2 [details])
Icons and compact mode is better, but still not perfect. (attachment3 [details]). 

Dragging in other apps, e.g. VSCode, looks ok. (attachment4 [details])

Tested in X11 and Wayland. Same problem.

I'm using 250% zoom. Maybe this has something to do with it? (the text looks quite like rendered in low resolution and upscaled 250%).

(As a sidenote, as you can see in attachment3 [details], the "desktop" icon has a grey-out effect when selected, only in icons mode. Other two modes, or other desktop icons, don't have this effect. Not sure if this is intended or not.) 

STEPS TO REPRODUCE
1. Open Dolphin.
2. Switch to details mode.
3. Drag a single file.

OBSERVED RESULT
Icon and text has jagged edge.

EXPECTED RESULT
Icon and text is as smooth as the drag source.

SOFTWARE/OS VERSIONS
Windows: 
macOS: 
Linux/KDE Plasma: 
(available in About System)
KDE Plasma Version: 5.23.2
KDE Frameworks Version: 21.08.3
Qt Version: 5.15.2

ADDITIONAL INFORMATION