Add UI Scale dropdown to the settings menu.

OpenRA.Game/Graphics/PlatformInterfaces.cs

@@ -57,6 +57,7 @@ namespace OpenRA
 		IHardwareCursor CreateHardwareCursor(string name, Size size, byte[] data, int2 hotspot, bool pixelDouble);
 		void SetHardwareCursor(IHardwareCursor cursor);
 		void SetRelativeMouseMode(bool mode);
+		void SetScaleModifier(float scale);
 	}
 
 	public interface IGraphicsContext : IDisposable

OpenRA.Game/Renderer.cs

@@ -91,6 +91,11 @@ namespace OpenRA
 			return new Size(size.X, size.Y);
 		}
 
+		public void SetUIScale(float scale)
+		{
+			Window.SetScaleModifier(scale);
+		}
+
 		public void InitializeFonts(ModData modData)
 		{
 			if (Fonts != null)

OpenRA.Game/WorldViewportSizes.cs

@@ -10,6 +10,7 @@
 #endregion
 
 using System.Collections.Generic;
+using OpenRA.Primitives;
 
 namespace OpenRA
 {
@@ -23,6 +24,8 @@ namespace OpenRA
 		public readonly int MaxZoomWindowHeight = 240;
 		public readonly bool AllowNativeZoom = true;
 
+		public readonly Size MinEffectiveResolution = new Size(1024, 720);
+
 		public int2 GetSizeRange(WorldViewport distance)
 		{
 			return distance == WorldViewport.Close ? CloseWindowHeights