opacity property

@override double opacity

The fraction to scale the child's alpha value.

An opacity of 1.0 is fully opaque. An opacity of 0.0 is fully transparent (i.e., invisible).

The opacity must not be null.

Values 1.0 and 0.0 are painted with a fast path. Other values require painting the child into an intermediate buffer, which is expensive.

Implementation

@override
double get opacity => _opacity ?? 1.0;

void opacity=(double? value)

Implementation

set opacity(double? value) {
  if (_opacity == value) return;

  _opacity = value;
  int alpha = ui.Color.getAlphaFromOpacity(opacity);
  renderBoxModel!.alpha = alpha;

  // Mark the compositing state for this render object as dirty
  // cause it will create new layer when opacity is valid.
  if (alpha != 0 && alpha != 255) {
    renderBoxModel?.markNeedsCompositingBitsUpdate();
  }
  // Opacity effect the stacking context.
  RenderBoxModel? parentRenderer = parent?.renderBoxModel;
  if (parentRenderer is RenderLayoutBox) {
    parentRenderer.markChildrenNeedsSort();
  }

  renderBoxModel?.markNeedsPaint();
}