performLayout method

@override Size performLayout(BoxConstraints constraints)

Hook for subclasses to perform layout within the given constraints.

Implementation

@override
Size performLayout(BoxConstraints constraints) {
  final textWidget = widget as Text;
  final width = constraints.maxWidth == BoxConstraints.infinity
      ? 999999
      : constraints.maxWidth;

  List<String> textLines;
  if (!textWidget.wrap) {
    textLines = [textWidget.data];
  } else {
    textLines = textWidget._wrapText(textWidget.data, width);
  }

  final limit = textWidget.maxLines != null
      ? min(textWidget.maxLines!, textLines.length)
      : textLines.length;

  var measuredWidth = 0;
  final lineMeasurements = <int>[];
  for (var i = 0; i < limit; i++) {
    final lineW = measureStringWidth(textLines[i]);
    lineMeasurements.add(lineW);
    if (lineW > measuredWidth) {
      measuredWidth = lineW;
    }
  }

  final height = limit;
  final resolvedSize = constraints.constrain(Size(measuredWidth, height));

  // Now that final size is known, precompute render lines
  _cachedLines = [];
  final areaWidth = resolvedSize.width;
  for (var i = 0; i < limit; i++) {
    final line = textLines[i];
    final lineWidth = lineMeasurements[i];

    final startX = switch (textWidget.textAlign) {
      TextAlign.left || TextAlign.justify => 0,
      TextAlign.right => max(0, areaWidth - lineWidth),
      TextAlign.center => max(0, (areaWidth - lineWidth) ~/ 2),
    };

    final availableWidth = areaWidth - startX;
    final visibleChars = lineWidth > availableWidth
        ? textWidget._truncateToWidth(line, availableWidth)
        : line;
    _cachedLines.add(_RenderLine(visibleChars, startX));
  }

  return resolvedSize;
}