io/router: don't trigger redraw for handler reset events

key.InputOp and pointer.InputOp handlers are reset on first registration
through a key.FocusEvent{false} or pointer.Cancel, respectively.

However, the mere act of registering a handle shouldn't result in a
redraw. This is particularly true for misconfigured handlers where a new
tag is supplied every frame, resulting in continously redrawing.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

io/router/pointer.go

@@ -145,7 +145,9 @@ func (q *pointerQueue) collectHandlers(r *ops.Reader, events *handlerEvents) {
 			if !ok {
 				h = new(pointerHandler)
 				q.handlers[op.Tag] = h
-				events.Add(op.Tag, pointer.Event{Type: pointer.Cancel})
+				// Cancel handlers on (each) first appearance, but don't
+				// trigger redraw.
+				events.AddNoRedraw(op.Tag, pointer.Event{Type: pointer.Cancel})
 			}
 			h.active = true
 			h.area = state.area