app: use empty frame when FrameEvent.Frame isn't called

Signed-off-by: Elias Naur <[email protected]>

app/window.go

@@ -108,11 +108,12 @@ type Window struct {
 }
 
 type eventSummary struct {
- wakeup bool
- cfg *ConfigEvent
- view *ViewEvent
- frame *frameEvent
- destroy *DestroyEvent
+ wakeup bool
+ cfg *ConfigEvent
+ view *ViewEvent
+ frame *frameEvent
+ framePending bool
+ destroy *DestroyEvent
 }
 
 type callbacks struct {
@@ -219,6 +220,7 @@ func (w *Window) frame(frame *op.Ops, viewport image.Point) error {
 }
 
 func (w *Window) processFrame(frame *op.Ops, ack chan<- struct{}) {
+ w.coalesced.framePending = false
  wrapper := &w.decorations.Ops
  off := op.Offset(w.lastFrame.off).Push(wrapper)
  ops.AddCall(&wrapper.Internal, &frame.Internal, ops.PC{}, ops.PCFor(&frame.Internal))
@@ -563,6 +565,10 @@ func (w *Window) nextEvent() (event.Event, bool) {
  s.wakeup = false
  }()
  switch {
+ case s.framePending:
+ // If the user didn't call FrameEvent.Event, process
+ // an empty frame.
+ w.processFrame(new(op.Ops), nil)
  case s.view != nil:
  e := *s.view
  s.view = nil
@@ -579,6 +585,7 @@ func (w *Window) nextEvent() (event.Event, bool) {
  case s.frame != nil:
  e := *s.frame
  s.frame = nil
+ s.framePending = true
  return e.FrameEvent, true
  case s.wakeup:
  return wakeupEvent{}, true