I just noticed that widget/public/nsGUIEvent.h/NS_IS_MOUSE_EVENT() is checking for the usual mouse events but is not checking for double-clicks or "clicks": #define NS_MOUSE_LEFT_DOUBLECLICK (NS_MOUSE_MESSAGE_START + 24) #define NS_MOUSE_MIDDLE_DOUBLECLICK (NS_MOUSE_MESSAGE_START + 25) #define NS_MOUSE_RIGHT_DOUBLECLICK (NS_MOUSE_MESSAGE_START + 26) #define NS_MOUSE_LEFT_CLICK (NS_MOUSE_MESSAGE_START + 27) #define NS_MOUSE_MIDDLE_CLICK (NS_MOUSE_MESSAGE_START + 28) #define NS_MOUSE_RIGHT_CLICK (NS_MOUSE_MESSAGE_START + 29) and .. NS_MOUSE_MESSAGE_START is missing too. Not sure if this is important, might want to put a comment in there if there's a reason for omitting these.

Just oversights. I've fixed the macro. This is a code level fix so just trust me, its fixed.

I'll trust joki on this one...marking verified...