alpha method

void alpha({
  1. required int alpha,
  2. required VoidCallback paint,
  3. Offset offset = Offset.zero,
  4. Rect? bounds,
  5. LayerKey<Layer>? key,
})

Pushes an OpacityLayer to the compositing tree, calling paint to paint on top of the layer.

The alpha argument is the alpha value to use when blending. An alpha value of 0 means the painting is fully transparent and an alpha value of 255 means the painting is fully opaque.

The bounds argument defines the bounds in which the paint should paint, this is useful for debugging tools and does not affect rendering.

See also:

Implementation

void alpha({
  required int alpha,
  required VoidCallback paint,
  Offset offset = Offset.zero,
  Rect? bounds,
  LayerKey? key,
}) {
  OpacityLayer layer;
  if (key?.layer is OffsetLayer) {
    layer = (key!.layer! as OpacityLayer)..alpha = alpha;
  } else {
    layer = OpacityLayer(alpha: alpha);
    key?.layer = layer;
  }
  push(layer: layer, paint: paint, offset: offset, bounds: bounds);
}