context: #region Copyright & License Information
  /*
   * Copyright 2007-2016 The OpenRA Developers (see AUTHORS)
   * This file is part of OpenRA, which is free software. It is made
   * available to you under the terms of the GNU General Public License
   * as published by the Free Software Foundation, either version 3 of
   * the License, or (at your option) any later version. For more
   * information, see COPYING.
   */
  #endregion
  
  using System;
  using System.Collections.Generic;
  using System.Drawing;
  using System.Linq;
  
  namespace OpenRA.Graphics
  {
  	[Flags]
  	public enum ScrollDirection { None = 0, Up = 1, Left = 2, Down = 4, Right = 8 }
  
  	public static class ViewportExts
  	{
  		public static bool Includes(this ScrollDirection d, ScrollDirection s)
  		{
  			// PERF: Enum.HasFlag is slower and requires allocations.
  			return (d & s) == s;
  		}
  
  		public static ScrollDirection Set(this ScrollDirection d, ScrollDirection s, bool val)
  		{
  			return (d.Includes(s) != val) ? d ^ s : d;
  		}
  	}
  
  	public class Viewport
  	{
  		readonly WorldRenderer worldRenderer;
  
  		// Map bounds (world-px)
  		readonly Rectangle mapBounds;
  		readonly Size tileSize;
  
  		// Viewport geometry (world-px)
  		public int2 CenterLocation { get; private set; }
  
  		public WPos CenterPosition { get { return worldRenderer.ProjectedPosition(CenterLocation); } }
  
  		public int2 TopLeft { get { return CenterLocation - viewportSize / 2; } }
  		public int2 BottomRight { get { return CenterLocation + viewportSize / 2; } }
  		int2 viewportSize;
  		ProjectedCellRegion cells;
  		bool cellsDirty = true;
  
  		ProjectedCellRegion allCells;
  		bool allCellsDirty = true;
  		readonly float[] availableZoomSteps = new[] { 2f, 1f, 0.5f, 0.25f };
  
  		float zoom = 1f;
  
  		public float[] AvailableZoomSteps
  		{
  			get { return availableZoomSteps; }
  		}
  
  		public float Zoom
  		{
  			get
  			{
  				return zoom;
  			}
  
  			set
  			{
  				var newValue = ClosestTo(AvailableZoomSteps, value);
  				zoom = newValue;
  				viewportSize = (1f / zoom * new float2(Game.Renderer.Resolution)).ToInt2();
  				cellsDirty = true;
  				allCellsDirty = true;
  			}
  		}
  
  		public static long TicksSinceLastMove = 0;
  		public static int2 LastMousePos;
  
  		float ClosestTo(float[] collection, float target)
  		{
  			var closestValue = collection.First();
  			var subtractResult = Math.Abs(closestValue - target);
  
  			foreach (var element in collection)
  			{
  				if (Math.Abs(element - target) < subtractResult)
  				{
  					subtractResult = Math.Abs(element - target);
  					closestValue = element;
  				}
  			}
  
  			return closestValue;
  		}
  
  		public ScrollDirection GetBlockedDirections()
  		{
  			var ret = ScrollDirection.None;
  			if (CenterLocation.Y <= mapBounds.Top)
  				ret |= ScrollDirection.Up;
  			if (CenterLocation.X <= mapBounds.Left)
  				ret |= ScrollDirection.Left;
  			if (CenterLocation.Y >= mapBounds.Bottom)
  				ret |= ScrollDirection.Down;
  			if (CenterLocation.X >= mapBounds.Right)
  				ret |= ScrollDirection.Right;
  
  			return ret;
  		}
  
  		public Viewport(WorldRenderer wr, Map map)
  		{
  			worldRenderer = wr;
  			var grid = Game.ModData.Manifest.Get<MapGrid>();
  
  			// Calculate map bounds in world-px
  			if (wr.World.Type == WorldType.Editor)
  			{
  				// The full map is visible in the editor
  				var width = map.MapSize.X * grid.TileSize.Width;
  				var height = map.MapSize.Y * grid.TileSize.Height;
  				if (wr.World.Map.Grid.Type == MapGridType.RectangularIsometric)
  					height /= 2;
  
  				mapBounds = new Rectangle(0, 0, width, height);
  				CenterLocation = new int2(width / 2, height / 2);
  			}
  			else
  			{
  				var tl = wr.ScreenPxPosition(map.ProjectedTopLeft);
  				var br = wr.ScreenPxPosition(map.ProjectedBottomRight);
  				mapBounds = Rectangle.FromLTRB(tl.X, tl.Y, br.X, br.Y);
  				CenterLocation = (tl + br) / 2;
  			}
  
  			Zoom = Game.Settings.Graphics.PixelDouble ? 2 : 1;
  			tileSize = grid.TileSize;
  		}
  
  		public CPos ViewToWorld(int2 view)
  		{
  			var world = worldRenderer.Viewport.ViewToWorldPx(view);
  			var map = worldRenderer.World.Map;
  			var candidates = CandidateMouseoverCells(world).ToList();
  			var tileSet = worldRenderer.World.Map.Rules.TileSet;
  
  			foreach (var uv in candidates)
  			{
  				// Coarse filter to nearby cells
  				var p = map.CenterOfCell(uv.ToCPos(map.Grid.Type));
  				var s = worldRenderer.ScreenPxPosition(p);
  				if (Math.Abs(s.X - world.X) <= tileSize.Width && Math.Abs(s.Y - world.Y) <= tileSize.Height)
  				{
  					var ramp = 0;
  					if (map.Contains(uv))
  					{
  						var ti = tileSet.GetTileInfo(map.Tiles[uv]);
  						if (ti != null)
  							ramp = ti.RampType;
  					}
  
  					var corners = map.Grid.CellCorners[ramp];
  					var pos = map.CenterOfCell(uv.ToCPos(map));
  					var screen = corners.Select(c => worldRenderer.ScreenPxPosition(pos + c)).ToArray();
  
  					if (screen.PolygonContains(world))
  						return uv.ToCPos(map);
  				}
  			}
  
  			// Mouse is not directly over a cell (perhaps on a cliff)
  			// Try and find the closest cell
  			if (candidates.Count > 0)
  			{
  				return candidates.OrderBy(uv =>
  				{
  					var p = map.CenterOfCell(uv.ToCPos(map.Grid.Type));
  					var s = worldRenderer.ScreenPxPosition(p);
  					var dx = Math.Abs(s.X - world.X);
  					var dy = Math.Abs(s.Y - world.Y);
  
  					return dx * dx + dy * dy;
  				}).First().ToCPos(map);
  			}
  
  			// Something is very wrong, but lets return something that isn't completely bogus and hope the caller can recover
  			return worldRenderer.World.Map.CellContaining(worldRenderer.ProjectedPosition(ViewToWorldPx(view)));
  		}
  
  		/// <summary> Returns an unfiltered list of all cells that could potentially contain the mouse cursor</summary>
  		IEnumerable<MPos> CandidateMouseoverCells(int2 world)
  		{
  			var map = worldRenderer.World.Map;
  			var minPos = worldRenderer.ProjectedPosition(world);
  
  			// Find all the cells that could potentially have been clicked
  			var a = map.CellContaining(minPos - new WVec(1024, 0, 0)).ToMPos(map.Grid.Type);
  			var b = map.CellContaining(minPos + new WVec(512, 512 * map.Grid.MaximumTerrainHeight, 0)).ToMPos(map.Grid.Type);
  
  			for (var v = b.V; v >= a.V; v--)
  				for (var u = b.U; u >= a.U; u--)
  
gt: 					yield return new MPos(u, v);