From cd238e9ea575b0d6ea83065a8d13f54f431e364f Mon Sep 17 00:00:00 2001
From: Evan Hemsley <evan@moonside.games>
Date: Fri, 17 Jul 2020 13:52:05 -0700
Subject: [PATCH] scaler script

---
 ResolutionScaler.cs | 68 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100644 ResolutionScaler.cs

diff --git a/ResolutionScaler.cs b/ResolutionScaler.cs
new file mode 100644
index 0000000..f807056
--- /dev/null
+++ b/ResolutionScaler.cs
@@ -0,0 +1,68 @@
+using Microsoft.Xna.Framework;
+
+namespace ResolutionScaler
+{
+    static class ResolutionScaler
+    {
+        static private int s_virtual_width;
+        static private int s_virtual_height;
+        static private int s_screen_width;
+        static private int s_screen_height;
+
+        static private Matrix s_transform_matrix;
+        static private bool s_dirtyMatrix = true;
+
+        static public void Init(int screenWidth, int screenHeight, int virtualWidth, int virtualHeight)
+        {
+            s_screen_width = screenWidth;
+            s_screen_height = screenHeight;
+            s_virtual_width = virtualWidth;
+            s_virtual_height = virtualHeight;
+            s_dirtyMatrix = true;
+        }
+
+        static public Matrix TransformMatrix
+        {
+            get
+            {
+                if (s_dirtyMatrix) RecreateScaleMatrix();
+                return s_transform_matrix;
+            }
+        }
+
+        static public void SetScreenResolution(int width, int height)
+        {
+            s_screen_width = width;
+            s_screen_height = height;
+            s_dirtyMatrix = true;
+        }
+
+        static public void SetVirtualResolution(int width, int height)
+        {
+            s_virtual_width = width;
+            s_virtual_height = height;
+            s_dirtyMatrix = true;
+        }
+
+        static private void RecreateScaleMatrix()
+        {
+            var scaleUniform = System.Math.Min(
+                (float)s_screen_width / s_virtual_width,
+                (float)s_screen_height / s_virtual_height
+            );
+
+            var scaleMatrix = Matrix.CreateScale(
+                (float)scaleUniform,
+                (float)scaleUniform,
+                1f
+            );
+
+            var offX = (s_screen_width - scaleUniform * s_virtual_width) / 2;
+            var offY = (s_screen_height - scaleUniform * s_virtual_height) / 2;
+            var translationMatrix = Matrix.CreateTranslation(offX, offY, 0);
+
+            s_transform_matrix = scaleMatrix * translationMatrix;
+            s_dirtyMatrix = false;
+        }
+    }
+}