io/router: [API] drop extra frame

This change removes the extra frame scheduled when events was delivered
during a frame. This extra frame was intended to paper over state changes
that happen later than the layout depending on it.

However, it is better for programs to never allow such state change skew,
and recent changes allows them to refresh and query state before layout.

This is an API change because programs may rely on the extra frames.
Those programs should ensure that state is updated before relying on it
in layout.

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

io/router/key_test.go

@@ -30,11 +30,6 @@ func TestKeyWakeup(t *testing.T) {
 	if evts := r.Events(handler); len(evts) != 1 {
 		t.Errorf("no Focus event for newly registered key.InputOp")
 	}
-	// Verify that r.Events does trigger a redraw.
-	r.Frame(&ops)
-	if _, wake := r.WakeupTime(); !wake {
-		t.Errorf("key.FocusEvent event didn't trigger a redraw")
-	}
 }
 
 func TestKeyMultiples(t *testing.T) {

io/router/pointer_test.go

@@ -33,11 +33,6 @@ func TestPointerWakeup(t *testing.T) {
 	}
 	// However, adding a handler queues a Cancel event.
 	assertEventPointerTypeSequence(t, r.Events(handler), pointer.Cancel)
-	// Verify that r.Events does trigger a redraw.
-	r.Frame(&ops)
-	if _, wake := r.WakeupTime(); !wake {
-		t.Errorf("pointer.Cancel event didn't trigger a redraw")
-	}
 }
 
 func TestPointerDrag(t *testing.T) {

io/router/router.go

@@ -593,16 +593,6 @@ func (h *handlerEvents) HadEvents() bool {
 func (h *handlerEvents) Events(k event.Tag) []event.Event {
 	if events, ok := h.handlers[k]; ok {
 		h.handlers[k] = h.handlers[k][:0]
-		// Schedule another frame if we delivered events to the user
-		// to flush half-updated state. This is important when an
-		// event changes UI state that has already been laid out. In
-		// the worst case, we waste a frame, increasing power usage.
-		//
-		// Gio is expected to grow the ability to construct
-		// frame-to-frame differences and only render to changed
-		// areas. In that case, the waste of a spurious frame should
-		// be minimal.
-		h.hadEvents = h.hadEvents || len(events) > 0
 		return events
 	}
 	return nil