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 sb = widget as ScrollBar;
  sb._lastArea = Rect(offset.dx, offset.dy, size.width, size.height);

  if (size.width <= 0 || size.height <= 0) return;
  final total = sb._totalExtent;
  if (total <= 0) return;

  if (sb.direction == LayoutDirection.vertical) {
    for (var y = 0; y < trackHeight; y++) {
      final isThumb = y >= thumbPos && y < thumbPos + thumbHeight;
      final style = isThumb ? sb.thumbStyle : sb.trackStyle;
      buffer.setAttributes(
        offset.dx,
        offset.dy + y,
        char: isThumb ? sb.thumbChar : sb.trackChar,
        fg: style.foreground?.argb ?? 0,
        bg: style.background?.argb ?? 0,
        modifiers: style.modifiers,
      );
    }
  } else {
    for (var x = 0; x < trackHeight; x++) {
      final isThumb = x >= thumbPos && x < thumbPos + thumbHeight;
      final style = isThumb ? sb.thumbStyle : sb.trackStyle;
      buffer.setAttributes(
        offset.dx + x,
        offset.dy,
        char: isThumb ? sb.thumbChar : sb.trackChar,
        fg: style.foreground?.argb ?? 0,
        bg: style.background?.argb ?? 0,
        modifiers: style.modifiers,
      );
    }
  }
}