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// 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 'dart:math' as math;
import 'package:flutter/foundation.dart' show clampDouble;
import 'basic_types.dart';
/// Position a child box within a container box, either above or below a target
/// point.
/// The container's size is described by `size`.
/// The target point is specified by `target`, as an offset from the top left of
/// the container.
/// The child box's size is given by `childSize`.
/// The return value is the suggested distance from the top left of the
/// container box to the top left of the child box.
/// The suggested position will be above the target point if `preferBelow` is
/// false, and below the target point if it is true, unless it wouldn't fit on
/// the preferred side but would fit on the other side.
/// The suggested position will place the nearest side of the child to the
/// target point `verticalOffset` from the target point (even if it cannot fit
/// given that constraint).
/// The suggested position will be at least `margin` away from the edge of the
/// container. If possible, the child will be positioned so that its center is
/// aligned with the target point. If the child cannot fit horizontally within
/// the container given the margin, then the child will be centered in the
/// container.
/// Used by [Tooltip] to position a tooltip relative to its parent.
/// The arguments must not be null.
Offset positionDependentBox({
required Size size,
required Size childSize,
required Offset target,
required bool preferBelow,
double verticalOffset = 0.0,
double margin = 10.0,
}) {
final bool fitsBelow = target.dy + verticalOffset + childSize.height <= size.height - margin;
final bool fitsAbove = target.dy - verticalOffset - childSize.height >= margin;
final bool tooltipBelow = fitsAbove == fitsBelow ? preferBelow : fitsBelow;
final double y;
if (tooltipBelow) {
y = math.min(target.dy + verticalOffset, size.height - margin);
} else {
y = math.max(target.dy - verticalOffset - childSize.height, margin);
final double flexibleSpace = size.width - childSize.width;
final double x = flexibleSpace <= 2 * margin
// If there's not enough horizontal space for margin + child, center the
// child.
? flexibleSpace / 2.0
: clampDouble(target.dx - childSize.width / 2, margin, flexibleSpace - margin);
return Offset(x, y);