onFrameComplete method

  1. @override
void onFrameComplete(
  1. void whenDone()
)
override

Runs whenDone once the GPU has finished with the frame being encoded now.

The one thing a caller cannot work out for itself. A finished frame is handed to the window as a texture the backend still owns, and drawing into that texture again while the compositor is reading it is a frame drawn half-and-half. The only defence without this is to keep N of them and hope N is enough — and what N has to be depends on the display's rate, the build's speed and how far behind the GPU is, none of which the engine knows. With this it does not have to guess: a texture goes back into rotation when the work that read it is done.

A backend whose submission is synchronous — the software rasteriser, and WebGL, where the canvas is composited by the browser — calls whenDone straight away, and is telling the truth when it does.

Implementation

@override
void onFrameComplete(void Function() whenDone) {
  if (completesImmediately) {
    whenDone();
    return;
  }
  pendingFrames.add(whenDone);
}