Add ability to draw a border around a set of adjacent cells.

OpenRA.Mods.Common/Graphics/BorderedRegionRenderable.cs

@@ -0,0 +1,98 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * 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.Collections.Generic;
+using System.Linq;
+using OpenRA.Graphics;
+using OpenRA.Primitives;
+
+namespace OpenRA.Mods.Common.Graphics
+{
+	public readonly struct BorderedRegionRenderable : IRenderable, IFinalizedRenderable
+	{
+		enum Corner { TopLeft, TopRight, BottomRight, BottomLeft }
+
+		// Maps a cell offset to the index of the corner (in the 'Corner' arrays in the MapGrid.CellRamp structs)
+		// from which a border should be drawn. The index of the end corner will be (cornerIndex + 1) % 4.
+		static readonly Dictionary<CVec, int> Offset2CornerIndex = new()
+		{
+			{ new CVec(0, -1), (int)Corner.TopLeft },
+			{ new CVec(1,  0), (int)Corner.TopRight },
+			{ new CVec(0,  1), (int)Corner.BottomRight },
+			{ new CVec(-1, 0), (int)Corner.BottomLeft },
+		};
+
+		readonly CPos[] region;
+		readonly Color color, contrastColor;
+		readonly float width, contrastWidth;
+
+		public BorderedRegionRenderable(CPos[] region, Color color, float width, Color contrastColor, float contrastWidth)
+		{
+			this.region = region;
+			this.color = color;
+			this.contrastColor = contrastColor;
+			this.width = width;
+			this.contrastWidth = contrastWidth;
+		}
+
+		readonly WPos IRenderable.Pos { get { return WPos.Zero; } }
+		readonly int IRenderable.ZOffset { get { return 0; } }
+		readonly bool IRenderable.IsDecoration { get { return true; } }
+
+		IRenderable IRenderable.WithZOffset(int newOffset) { return new BorderedRegionRenderable(region, color, width, contrastColor, contrastWidth); }
+		IRenderable IRenderable.OffsetBy(in WVec offset) { return new BorderedRegionRenderable(region, color, width, contrastColor, contrastWidth); }
+		IRenderable IRenderable.AsDecoration() { return this; }
+
+		IFinalizedRenderable IRenderable.PrepareRender(WorldRenderer wr) { return this; }
+		void IFinalizedRenderable.Render(WorldRenderer wr) { Draw(wr, region, color, width, contrastColor, contrastWidth); }
+		void IFinalizedRenderable.RenderDebugGeometry(WorldRenderer wr) { }
+		Rectangle IFinalizedRenderable.ScreenBounds(WorldRenderer wr) { return Rectangle.Empty; }
+
+		public static void Draw(WorldRenderer wr, CPos[] region, Color color, float width, Color constrastColor, float constrastWidth)
+		{
+			if (width == 0 && constrastWidth == 0)
+				return;
+
+			var map = wr.World.Map;
+			var cr = Game.Renderer.RgbaColorRenderer;
+
+			foreach (var c in region)
+			{
+				var mpos = c.ToMPos(map);
+				if (!map.Height.Contains(mpos) || wr.World.ShroudObscures(c))
+					continue;
+
+				var tile = map.Tiles[mpos];
+				var ti = map.Rules.TerrainInfo.GetTerrainInfo(tile);
+				var ramp = ti?.RampType ?? 0;
+
+				var corners = map.Grid.Ramps[ramp].Corners;
+				var pos = map.CenterOfCell(c) - new WVec(0, 0, map.Grid.Ramps[ramp].CenterHeightOffset);
+
+				foreach (var o in Offset2CornerIndex)
+				{
+					// If the neighboring cell is part of the region, don't draw a border between the cells.
+					if (region.Contains(c + o.Key))
+						continue;
+
+					var start = wr.Viewport.WorldToViewPx(wr.Screen3DPosition(pos + corners[o.Value]));
+					var end = wr.Viewport.WorldToViewPx(wr.Screen3DPosition(pos + corners[(o.Value + 1) % 4]));
+
+					if (constrastWidth > 0)
+						cr.DrawLine(start, end, constrastWidth, constrastColor);
+
+					if (width > 0)
+						cr.DrawLine(start, end, width, color);
+				}
+			}
+		}
+	}
+}