In 4.8.80-2 with Qt graphic system: Native, when pulling a window to the edge of the screen in order to tile it. kwin shows a white/black solid rectangle instead of a transparent one at the new location of the window. works fine for Raster.
Steps to Reproduce:
1. qt graphic system: native for kwin
2. pull a window to the edge
a solid rectangle is shown
should be a transparent rectangle
*** This bug has been marked as a duplicate of bug 301068 ***