Fix map preview bounds calculation.

OpenRA.Game/Map/Map.cs

@@ -713,11 +713,34 @@ namespace OpenRA
 
 			var isRectangularIsometric = Grid.Type == MapGridType.RectangularIsometric;
 
-			// Fudge the heightmap offset by adding as much extra as we need / can.
+			var top = int.MaxValue;
-			// This tries to correct for our incorrect assumption that MPos == PPos
+			var bottom = int.MinValue;
-			var heightOffset = Math.Min(Grid.MaximumTerrainHeight, MapSize.Y - Bounds.Bottom);
+
+			if (Grid.MaximumTerrainHeight > 0)
+			{
+				// The minimap is drawn in cell space, so we need to
+				// unproject the PPos bounds to find the MPos boundaries.
+				// This matches the calculation in RadarWidget that is used ingame
+				for (var x = Bounds.Left; x < Bounds.Right; x++)
+				{
+					var allTop = Unproject(new PPos(x, Bounds.Top));
+					var allBottom = Unproject(new PPos(x, Bounds.Bottom));
+					if (allTop.Any())
+						top = Math.Min(top, allTop.MinBy(uv => uv.V).V);
+
+					if (allBottom.Any())
+						bottom = Math.Max(bottom, allBottom.MaxBy(uv => uv.V).V);
+				}
+			}
+			else
+			{
+				// If the mod uses flat maps, MPos == PPos and we can take the bounds rect directly
+				top = Bounds.Top;
+				bottom = Bounds.Bottom;
+			}
+
 			var width = Bounds.Width;
-			var height = Bounds.Height + heightOffset;
+			var height = bottom - top;
 
 			var bitmapWidth = width;
 			if (isRectangularIsometric)
@@ -726,13 +749,13 @@ namespace OpenRA
 			var stride = bitmapWidth * 4;
 			var pxStride = 4;
 			var minimapData = new byte[stride * height];
-			(Color Left, Color Right) terrainColor = default((Color, Color));
+			(Color Left, Color Right) terrainColor = default;
 
 			for (var y = 0; y < height; y++)
 			{
 				for (var x = 0; x < width; x++)
 				{
-					var uv = new MPos(x + Bounds.Left, y + Bounds.Top);
+					var uv = new MPos(x + Bounds.Left, y + top);
 
 					// FirstOrDefault will return a (MPos.Zero, Color.Transparent) if positions is empty
 					var actorColor = positions.FirstOrDefault(ap => ap.Position == uv).Color;

OpenRA.Mods.Common/Widgets/RadarWidget.cs

@@ -193,7 +193,7 @@ namespace OpenRA.Mods.Common.Widgets
 					top = Math.Min(top, allTop.MinBy(uv => uv.V).V);
 
 				if (allBottom.Any())
-					bottom = Math.Max(bottom, allBottom.MinBy(uv => uv.V).V);
+					bottom = Math.Max(bottom, allBottom.MaxBy(uv => uv.V).V);
 			}
 
 			var b = Rectangle.FromLTRB(left, top, right, bottom);