AnimatedSampler class

A widget that allows access to a snapshot of the child widgets for painting with a sampler applied to a FragmentProgram.

When enabled is true, the child widgets will be painted into a texture exposed as a ui.Image. This can then be passed to a FragmentShader instance via FragmentShader.setSampler.

If enabled is false, then the child widgets are painted as normal.

Caveats:

• Platform views cannot be captured in a texture. If any are present they will be excluded from the texture. Texture-based platform views are OK.

Example:

Providing an image to a fragment shader using FragmentShader.setImageSampler.

Widget build(BuildContext context) {
  return AnimatedSampler(
    (ui.Image image, Size size, Canvas canvas) {
      shader
        ..setFloat(0, size.width)
        ..setFloat(1, size.height)
        ..setImageSampler(0, image);
      canvas.drawRect(Offset.zero & size, Paint()..shader = shader);
    },
    child: widget.child,
  );
}

See also:

• SnapshotWidget, which provides a similar API for the purpose of caching during expensive animations.