performPaint method

@override void performPaint(Buffer buffer, Offset offset)

Hook for subclasses to implement actual painting.

Implementation

@override
void performPaint(Buffer buffer, Offset offset) {
  final w = size.width;
  final h = size.height;
  if (w <= 0 || h <= 0) return;

  final widget = this.widget as SubpixelRippleWidget;
  final manager = widget.manager;

  final now = DateTime.now().millisecondsSinceEpoch;
  manager.updateRipples(now);
  if (!manager.hasActiveRipples) return;

  final canvas = Canvas(w, h, onlyDrawOnSpaces: true);
  var hasPainted = false;

  for (final ripple in manager.ripples) {
    final elapsed = now - ripple.startTime;
    if (elapsed < 0) continue;

    final progress = (elapsed / ripple.durationMs).clamp(0.0, 1.0);
    final radius = (progress * 16).round();

    if (radius > 0) {
      final Color(:r, :g, :b) = ripple.color;
      final fade = (255 * (1.0 - progress)).round().clamp(0, 255);
      final style = Style(
        foreground: Color(
          (r * fade) ~/ 255,
          (g * fade) ~/ 255,
          (b * fade) ~/ 255,
        ),
      );

      canvas.drawCircle(
        (ripple.center.x - 1) * 2 + 1,
        (ripple.center.y - 1) * 4 + 2,
        radius,
        cellStyle: style,
      );
      hasPainted = true;
    }
  }

  if (hasPainted) {
    final canvasEl = canvas.createElement();
    canvasEl.layout(BoxConstraints.tight(Size(w, h)));
    canvasEl.paint(buffer, offset);
    canvasEl.unmount();
  }
}