format method

@override BlockElement format(double availableWidth)

Converts this node into a BlockElement.

All late variables must be initialized prior to calling this method.

Implementation

@override
BlockElement format(double availableWidth) {
  final layoutBuilder = child.layoutBuilder;
  final blockWidth = availableWidth;
  final contentWidth = blockWidth - style.padding.horizontal;

  final lines = <InlineTextElement>[];
  final horizontalOffset = style.padding.left;
  var verticalOffset = style.padding.top;
  final textAlign = style.textAlign ?? TextAlign.left;
  while (!layoutBuilder.isDone) {
    final element = layoutBuilder.layOutNextLine(
      contentWidth,
      isStartOfLine: true,
    );
    if (element == null) {
      // Not enough horizontal space to lay out. For now we just stop the
      // layout altogether cutting off the remainder of the content. But is
      // there a better alternative?
      break;
    } else {
      final metrics = element.metrics;
      assert(metrics.left == 0 && metrics.baseline == 0);

      final dx = horizontalOffset +
          (contentWidth - metrics.width) * _relativeOffset(textAlign);
      final dy = verticalOffset + metrics.ascent;
      element.translate(dx, dy);

      lines.add(element);
      verticalOffset += metrics.height;
    }
  }
  verticalOffset += style.padding.bottom;
  final bg = makeBackground(style.background, blockWidth, verticalOffset);
  final elements = bg == null ? lines : [bg, ...lines];
  return GroupElement(
    width: blockWidth,
    height: verticalOffset,
    children: elements,
  );
}