Don't set a Window Icon on Plamsa::Dialog
Review Request #128484 - Created July 19, 2016 and discarded
It's practically never visible. Window flags are always masked with FramelessWindowHint and we always have the state NET::SkipTaskbar | NET::SkipPager set. (There is theoretically a code path that would allow an icon to be visible in some kwin effects that overlay icons..but not triggerable by anything in Plasma, at which point why would you want a Plasma icon anyway) This saves a bit of memory (up to 512K) as window icons are always loaded at every size to set the _NET_WM_ICON.
In KWin it can be seen when e.g. activating Present Windows while Kickoff is open or the calendar. Also in Alt+Tab this could happen.
KWin will show an icon - always - in the worst case it will be the generic X icon. If we go for that we must make sure that Plasma window are excluded from all KWin elements.