app,app/internal/gpu: process frame in parallel

A frame ops buffers is tracersed twice: once for GPU commands,
and once for everything else. There is already a GPU goroutine for
concurrentl issuing of GPU commands; move the frame ops processing
to the goroutine as well. Both frame ops passed can then proceed
in parallel.

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

app/window.go

@@ -122,7 +122,7 @@ func (w *Window) update(frame *op.Ops) {
 }
 
 func (w *Window) draw(frameStart time.Time, size image.Point, frame *op.Ops) {
-	w.gpu.Draw(w.queue.q.Profiling(), size, frame)
+	sync := w.gpu.Draw(w.queue.q.Profiling(), size, frame)
 	w.queue.q.Frame(frame)
 	switch w.queue.q.TextInputState() {
 	case input.TextInputOpen:
@@ -141,6 +141,8 @@ func (w *Window) draw(frameStart time.Time, size image.Point, frame *op.Ops) {
 		w.setNextFrame(t)
 	}
 	w.updateAnimation()
+	// Wait for the GPU goroutine to finish processing frame.
+	<-sync
 }
 
 // Invalidate the window such that a FrameEvent will be generated