// 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, }) { // VERTICAL DIRECTION 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); } // HORIZONTAL DIRECTION 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); }