The icons in Plasma context menus and global menu applet don't honor the scale factor set by kscreen. I'm using a high DPI screen with 2x scale factor and icons are tiny. It only affects Plasma; icons in context menu of Qt applications and in the global menu opened from the kwin button are correctly scaled.
*** This bug has been marked as a duplicate of bug 356446 ***
*** This bug has been marked as a duplicate of bug 366088 ***