[Gallery] Fix directory structure (#312)

gallery/lib/demos/reference/transformations_demo_board.dart

@@ -0,0 +1,289 @@
+// Copyright 2019 The Flutter team. 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:collection' show IterableMixin;
+import 'dart:math';
+import 'dart:ui' show Vertices;
+import 'package:flutter/material.dart' hide Gradient;
+import 'package:vector_math/vector_math_64.dart' show Vector3;
+
+// BEGIN transformationsDemo#2
+
+// The entire state of the hex board and abstraction to get information about
+// it. Iterable so that all BoardPoints on the board can be iterated over.
+@immutable
+class Board extends Object with IterableMixin<BoardPoint> {
+  Board({
+    @required this.boardRadius,
+    @required this.hexagonRadius,
+    @required this.hexagonMargin,
+    this.selected,
+    List<BoardPoint> boardPoints,
+  })  : assert(boardRadius > 0),
+        assert(hexagonRadius > 0),
+        assert(hexagonMargin >= 0) {
+    // Set up the positions for the center hexagon where the entire board is
+    // centered on the origin.
+    // Start point of hexagon (top vertex).
+    final Point<double> hexStart = Point<double>(0, -hexagonRadius);
+    final double hexagonRadiusPadded = hexagonRadius - hexagonMargin;
+    final double centerToFlat = sqrt(3) / 2 * hexagonRadiusPadded;
+    positionsForHexagonAtOrigin.addAll(<Offset>[
+      Offset(hexStart.x, hexStart.y),
+      Offset(hexStart.x + centerToFlat, hexStart.y + 0.5 * hexagonRadiusPadded),
+      Offset(hexStart.x + centerToFlat, hexStart.y + 1.5 * hexagonRadiusPadded),
+      Offset(hexStart.x + centerToFlat, hexStart.y + 1.5 * hexagonRadiusPadded),
+      Offset(hexStart.x, hexStart.y + 2 * hexagonRadiusPadded),
+      Offset(hexStart.x, hexStart.y + 2 * hexagonRadiusPadded),
+      Offset(hexStart.x - centerToFlat, hexStart.y + 1.5 * hexagonRadiusPadded),
+      Offset(hexStart.x - centerToFlat, hexStart.y + 1.5 * hexagonRadiusPadded),
+      Offset(hexStart.x - centerToFlat, hexStart.y + 0.5 * hexagonRadiusPadded),
+    ]);
+
+    if (boardPoints != null) {
+      _boardPoints.addAll(boardPoints);
+    } else {
+      // Generate boardPoints for a fresh board.
+      BoardPoint boardPoint = _getNextBoardPoint(null);
+      while (boardPoint != null) {
+        _boardPoints.add(boardPoint);
+        boardPoint = _getNextBoardPoint(boardPoint);
+      }
+    }
+  }
+
+  final int boardRadius; // Number of hexagons from center to edge.
+  final double hexagonRadius; // Pixel radius of a hexagon (center to vertex).
+  final double hexagonMargin; // Margin between hexagons.
+  final List<Offset> positionsForHexagonAtOrigin = <Offset>[];
+  final BoardPoint selected;
+  final List<BoardPoint> _boardPoints = <BoardPoint>[];
+
+  @override
+  Iterator<BoardPoint> get iterator => _BoardIterator(_boardPoints);
+
+  // For a given q axial coordinate, get the range of possible r values
+  // See the definition of BoardPoint for more information about hex grids and
+  // axial coordinates.
+  _Range _getRRangeForQ(int q) {
+    int rStart;
+    int rEnd;
+    if (q <= 0) {
+      rStart = -boardRadius - q;
+      rEnd = boardRadius;
+    } else {
+      rEnd = boardRadius - q;
+      rStart = -boardRadius;
+    }
+
+    return _Range(rStart, rEnd);
+  }
+
+  // Get the BoardPoint that comes after the given BoardPoint. If given null,
+  // returns the origin BoardPoint. If given BoardPoint is the last, returns
+  // null.
+  BoardPoint _getNextBoardPoint(BoardPoint boardPoint) {
+    // If before the first element.
+    if (boardPoint == null) {
+      return BoardPoint(-boardRadius, 0);
+    }
+
+    final _Range rRange = _getRRangeForQ(boardPoint.q);
+
+    // If at or after the last element.
+    if (boardPoint.q >= boardRadius && boardPoint.r >= rRange.max) {
+      return null;
+    }
+
+    // If wrapping from one q to the next.
+    if (boardPoint.r >= rRange.max) {
+      return BoardPoint(boardPoint.q + 1, _getRRangeForQ(boardPoint.q + 1).min);
+    }
+
+    // Otherwise we're just incrementing r.
+    return BoardPoint(boardPoint.q, boardPoint.r + 1);
+  }
+
+  // Check if the board point is actually on the board.
+  bool _validateBoardPoint(BoardPoint boardPoint) {
+    const BoardPoint center = BoardPoint(0, 0);
+    final int distanceFromCenter = getDistance(center, boardPoint);
+    return distanceFromCenter <= boardRadius;
+  }
+
+  // Get the distance between two BoardPoins.
+  static int getDistance(BoardPoint a, BoardPoint b) {
+    final Vector3 a3 = a.cubeCoordinates;
+    final Vector3 b3 = b.cubeCoordinates;
+    return ((a3.x - b3.x).abs() + (a3.y - b3.y).abs() + (a3.z - b3.z).abs()) ~/
+        2;
+  }
+
+  // Return the q,r BoardPoint for a point in the scene, where the origin is in
+  // the center of the board in both coordinate systems. If no BoardPoint at the
+  // location, return null.
+  BoardPoint pointToBoardPoint(Offset point) {
+    final BoardPoint boardPoint = BoardPoint(
+      ((sqrt(3) / 3 * point.dx - 1 / 3 * point.dy) / hexagonRadius).round(),
+      ((2 / 3 * point.dy) / hexagonRadius).round(),
+    );
+
+    if (!_validateBoardPoint(boardPoint)) {
+      return null;
+    }
+
+    return _boardPoints.firstWhere((boardPointI) {
+      return boardPointI.q == boardPoint.q && boardPointI.r == boardPoint.r;
+    });
+  }
+
+  // Return a scene point for the center of a hexagon given its q,r point.
+  Point<double> boardPointToPoint(BoardPoint boardPoint) {
+    return Point<double>(
+      sqrt(3) * hexagonRadius * boardPoint.q +
+          sqrt(3) / 2 * hexagonRadius * boardPoint.r,
+      1.5 * hexagonRadius * boardPoint.r,
+    );
+  }
+
+  // Get Vertices that can be drawn to a Canvas for the given BoardPoint.
+  Vertices getVerticesForBoardPoint(BoardPoint boardPoint, Color color) {
+    final Point<double> centerOfHexZeroCenter = boardPointToPoint(boardPoint);
+
+    final List<Offset> positions = positionsForHexagonAtOrigin.map((offset) {
+      return offset.translate(centerOfHexZeroCenter.x, centerOfHexZeroCenter.y);
+    }).toList();
+
+    return Vertices(
+      VertexMode.triangleFan,
+      positions,
+      colors: List<Color>.filled(positions.length, color),
+    );
+  }
+
+  // Return a new board with the given BoardPoint selected.
+  Board copyWithSelected(BoardPoint boardPoint) {
+    if (selected == boardPoint) {
+      return this;
+    }
+    final Board nextBoard = Board(
+      boardRadius: boardRadius,
+      hexagonRadius: hexagonRadius,
+      hexagonMargin: hexagonMargin,
+      selected: boardPoint,
+      boardPoints: _boardPoints,
+    );
+    return nextBoard;
+  }
+
+  // Return a new board where boardPoint has the given color.
+  Board copyWithBoardPointColor(BoardPoint boardPoint, Color color) {
+    final BoardPoint nextBoardPoint = boardPoint.copyWithColor(color);
+    final int boardPointIndex = _boardPoints.indexWhere((boardPointI) =>
+        boardPointI.q == boardPoint.q && boardPointI.r == boardPoint.r);
+
+    if (elementAt(boardPointIndex) == boardPoint && boardPoint.color == color) {
+      return this;
+    }
+
+    final List<BoardPoint> nextBoardPoints =
+        List<BoardPoint>.from(_boardPoints);
+    nextBoardPoints[boardPointIndex] = nextBoardPoint;
+    final BoardPoint selectedBoardPoint =
+        boardPoint == selected ? nextBoardPoint : selected;
+    return Board(
+      boardRadius: boardRadius,
+      hexagonRadius: hexagonRadius,
+      hexagonMargin: hexagonMargin,
+      selected: selectedBoardPoint,
+      boardPoints: nextBoardPoints,
+    );
+  }
+}
+
+class _BoardIterator extends Iterator<BoardPoint> {
+  _BoardIterator(this.boardPoints);
+
+  final List<BoardPoint> boardPoints;
+  int currentIndex;
+
+  @override
+  BoardPoint current;
+
+  @override
+  bool moveNext() {
+    if (currentIndex == null) {
+      currentIndex = 0;
+    } else {
+      currentIndex++;
+    }
+
+    if (currentIndex >= boardPoints.length) {
+      current = null;
+      return false;
+    }
+
+    current = boardPoints[currentIndex];
+    return true;
+  }
+}
+
+// A range of q/r board coordinate values.
+@immutable
+class _Range {
+  const _Range(this.min, this.max)
+      : assert(min != null),
+        assert(max != null),
+        assert(min <= max);
+
+  final int min;
+  final int max;
+}
+
+// A location on the board in axial coordinates.
+// Axial coordinates use two integers, q and r, to locate a hexagon on a grid.
+// https://www.redblobgames.com/grids/hexagons/#coordinates-axial
+@immutable
+class BoardPoint {
+  const BoardPoint(
+    this.q,
+    this.r, {
+    this.color = const Color(0xFFCDCDCD),
+  });
+
+  final int q;
+  final int r;
+  final Color color;
+
+  @override
+  String toString() {
+    return 'BoardPoint($q, $r, $color)';
+  }
+
+  // Only compares by location.
+  @override
+  bool operator ==(Object other) {
+    if (other.runtimeType != runtimeType) {
+      return false;
+    }
+    return other is BoardPoint && other.q == q && other.r == r;
+  }
+
+  @override
+  int get hashCode => hashValues(q, r);
+
+  BoardPoint copyWithColor(Color nextColor) =>
+      BoardPoint(q, r, color: nextColor);
+
+  // Convert from q,r axial coords to x,y,z cube coords.
+  Vector3 get cubeCoordinates {
+    return Vector3(
+      q.toDouble(),
+      r.toDouble(),
+      (-q - r).toDouble(),
+    );
+  }
+}
+
+// END