getPathBounds function

Rect getPathBounds(Path path)

Computes an axis-aligned bounding Rect that encloses the visible points of path.

This function iterates over the PathMetrics returned by path.computeMetrics() and samples points along each metric using tangents obtained via getTangentForOffset. Sampling is performed at a fixed number of steps (default 100) across each metric's length to approximate the visible extent of the path.

Important notes:

• The result is an approximation. Complex curves may have extrema between sampled points; increase the sample count if you need higher accuracy.
• If the path has no metrics or contains no sampled points, the function returns Rect.zero.
• Complexity: O(metrics * samples). For very large paths or a large sample count this may be costly; tune the sample count accordingly.

Example:

final bounds = getPathBounds(myPath);
final width = bounds.width;

Parameters:

• path: the Path to measure.

Returns:

• An axis-aligned Rect that contains sampled points of the path, or Rect.zero if none.

Implementation

Rect getPathBounds(Path path) {
  var minX = double.infinity;
  var minY = double.infinity;
  var maxX = double.negativeInfinity;
  var maxY = double.negativeInfinity;

  final pathMetrics = path.computeMetrics();
  const samples = 100;

  for (final metric in pathMetrics) {
    final length = metric.length;
    if (length <= 0) continue; // skip degenerate metrics

    final step = length / samples;
    for (var i = 0; i <= samples; i++) {
      final t = (i == samples) ? length : (i * step);
      final tangent = metric.getTangentForOffset(t);
      if (tangent != null) {
        final position = tangent.position;
        minX = min(minX, position.dx);
        minY = min(minY, position.dy);
        maxX = max(maxX, position.dx);
        maxY = max(maxY, position.dy);
      }
    }
  }

  if (minX == double.infinity || minY == double.infinity) {
    return Rect.zero; // Return empty rect if no points were sampled.
  }

  return Rect.fromLTRB(minX, minY, maxX, maxY);
}