Canvas and Mouse

This will work. when the $201 'mouse clicked' event occurs just check that the event source is the canvas as well:

canvas=CreateCanvas(...)

Repeat
 event=WaitEvent()
 Select event
  Case $201 ; mouse clicked
  mx=MouseX(canvas) : gy=MouseY(canvas)
  If EventSource()=canvas
   If EventData()=1 ;lmb
     ;;; LEFT BUTTON CLICKED IN CANVAS
   EndIf
   If EventData()=2 ;rmb
     ;;; RIGHT BUTTON CLICKED IN CANVAS
   EndIf
  EndIf
 End Select
Until quit=True