pushClipPath method Null safety

ClipPathEngineLayer? pushClipPath (
  1. Path path,
  2. {Clip clipBehavior: Clip.antiAlias,
  3. ClipPathEngineLayer? oldLayer}
)

Pushes a path clip operation onto the operation stack.

Rasterization outside the given path is discarded.

If oldLayer is not null the engine will attempt to reuse the resources allocated for the old layer when rendering the new layer. This is purely an optimization. It has no effect on the correctness of rendering.

Passing a layer to addRetained or as oldLayer argument to a push method counts as usage. A layer can be used no more than once in a scene. For example, it may not be passed simultaneously to two push methods, or to a push method and to addRetained.

When a layer is passed to addRetained all descendant layers are also considered as used in this scene. The same single-usage restriction applies to descendants.

When a layer is passed as an oldLayer argument to a push method, it may no longer be used in subsequent frames. If you would like to continue reusing the resources associated with the layer, store the layer object returned by the push method and use that in the next frame instead of the original object.

See pop for details about the operation stack. See Clip for different clip modes. By default, the clip will be anti-aliased (clip = Clip.antiAlias).

Implementation

ClipPathEngineLayer? pushClipPath(
  Path path, {
  Clip clipBehavior = Clip.antiAlias,
  ClipPathEngineLayer? oldLayer,
}) {
  assert(clipBehavior != null); // ignore: unnecessary_null_comparison
  assert(clipBehavior != Clip.none);
  assert(_debugCheckCanBeUsedAsOldLayer(oldLayer, 'pushClipPath'));
  final EngineLayer engineLayer = EngineLayer._();
  _pushClipPath(engineLayer, path, clipBehavior.index);
  final ClipPathEngineLayer layer = ClipPathEngineLayer._(engineLayer);
  assert(_debugPushLayer(layer));
  return layer;
}