io/pointer: add InputOp.Types to specify which types of events to receive

Signed-off-by: Gordon Klaus <gordon.klaus@gmail.com>

gesture/gesture.go

@@ -112,7 +112,10 @@ var touchSlop = unit.Dp(3)
 
 // Add the handler to the operation list to receive click events.
 func (c *Click) Add(ops *op.Ops) {
-	op := pointer.InputOp{Tag: c}
+	op := pointer.InputOp{
+		Tag:   c,
+		Types: pointer.Press | pointer.Release | pointer.Enter | pointer.Leave,
+	}
 	op.Add(ops)
 }
 
@@ -168,7 +171,11 @@ func (c *Click) Events(q event.Queue) []ClickEvent {
 
 // Add the handler to the operation list to receive scroll events.
 func (s *Scroll) Add(ops *op.Ops) {
-	oph := pointer.InputOp{Tag: s, Grab: s.grab}
+	oph := pointer.InputOp{
+		Tag:   s,
+		Grab:  s.grab,
+		Types: pointer.Press | pointer.Move | pointer.Release | pointer.Scroll,
+	}
 	oph.Add(ops)
 	if s.flinger.Active() {
 		op.InvalidateOp{}.Add(ops)