Qt components supporting a rubber band leave trails behind when scaled up

When the QT_SCALE_FACTOR environment variable is set to certain values, dragging a rubber band down or to the right works just fine. However, dragging the rubber band up or to the left works to begin with, but then leaves trails behind when you drag back down or to the right.

The exact scale factor needed to trigger this bug may vary, but on an HP Elitebook 8570p, and in a QEMU virtual machine with a 1366x768 screen, a scale factor of 1.5 did the trick for me. Another person who verified this bug had to set the scale to 1.7 to trigger it. The bug can be triggered in a Qt list widget, but that's not the only place where it happens. A sample file for replicating the bug is attached (list_widget.ui.zip) - you can run it with "QT_SCALE_FACTOR=1.7 designer list_widget.ui", preview it with "Ctrl+R", and draw selection rectangles inside the preview window. (Again, you may need to adjust the scale factor depending on your system).

This bug was originally filed against LXQt's PCManFM-Qt. Detailed info can be found here: https://github.com/lxqt/pcmanfm-qt/issues/1597