packages/flutter/lib/src/widgets/text_selection_toolbar_anchors.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/foundation.dart';
import 'package:flutter/rendering.dart';

/// The position information for a text selection toolbar.
///
/// Typically, a menu will attempt to position itself at [primaryAnchor], and
/// if that's not possible, then it will use [secondaryAnchor] instead, if it
/// exists.
///
/// See also:
///
///  * [AdaptiveTextSelectionToolbar.anchors], which is of this type.
@immutable
class TextSelectionToolbarAnchors {
  /// Creates an instance of [TextSelectionToolbarAnchors] directly from the
  /// anchor points.
  const TextSelectionToolbarAnchors({
    required this.primaryAnchor,
    this.secondaryAnchor,
  });

  /// Creates an instance of [TextSelectionToolbarAnchors] for some selection.
  factory TextSelectionToolbarAnchors.fromSelection({
    required RenderBox renderBox,
    required double startGlyphHeight,
    required double endGlyphHeight,
    required List<TextSelectionPoint> selectionEndpoints,
  }) {
    final Rect editingRegion = Rect.fromPoints(
      renderBox.localToGlobal(Offset.zero),
      renderBox.localToGlobal(renderBox.size.bottomRight(Offset.zero)),
    );

    if (editingRegion.left.isNaN || editingRegion.top.isNaN
      || editingRegion.right.isNaN || editingRegion.bottom.isNaN) {
      return const TextSelectionToolbarAnchors(primaryAnchor: Offset.zero);
    }

    final bool isMultiline = selectionEndpoints.last.point.dy - selectionEndpoints.first.point.dy >
        endGlyphHeight / 2;

    final Rect selectionRect = Rect.fromLTRB(
      isMultiline
          ? editingRegion.left
          : editingRegion.left + selectionEndpoints.first.point.dx,
      editingRegion.top + selectionEndpoints.first.point.dy - startGlyphHeight,
      isMultiline
          ? editingRegion.right
          : editingRegion.left + selectionEndpoints.last.point.dx,
      editingRegion.top + selectionEndpoints.last.point.dy,
    );

    return TextSelectionToolbarAnchors(
      primaryAnchor: Offset(
        selectionRect.left + selectionRect.width / 2,
        clampDouble(selectionRect.top, editingRegion.top, editingRegion.bottom),
      ),
      secondaryAnchor: Offset(
        selectionRect.left + selectionRect.width / 2,
        clampDouble(selectionRect.bottom, editingRegion.top, editingRegion.bottom),
      ),
    );
  }

  /// The location that the toolbar should attempt to position itself at.
  ///
  /// If the toolbar doesn't fit at this location, use [secondaryAnchor] if it
  /// exists.
  final Offset primaryAnchor;

  /// The fallback position that should be used if [primaryAnchor] doesn't work.
  final Offset? secondaryAnchor;
}