Right-clicking causes the caret to move (possibly to a different line), so it should cancel autocompletion mode.
Shouldn't that be inside the test? Performing a copy of the selection doesn't need to cancel autocompletion.
Yes, I suppose so.
I've also spotted another minor issue: it doesn't take the focus when the right button goes down.
Revised patch attached.
This patch only touches ScintillaWin.cxx and not ScintillaGTK.cxx :'(
Please, could we also have a fix for ScintillaGTK.cxx?