From 3a8defcf3f3881c567f4da759424327b5b07f0b5 Mon Sep 17 00:00:00 2001
From: Colin McMillen <colin@semicolin.games>
Date: Tue, 25 Feb 2020 20:23:42 -0500
Subject: [PATCH] Letterbox the scene if the aspect ratio is out-of-whack.

Fixes #23.

GitOrigin-RevId: 2da580115e44f2658e7f9b9d3d39a366d3a1bbfd
---
 Shared/Scene.cs | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/Shared/Scene.cs b/Shared/Scene.cs
index 70aa027..a08fb4f 100644
--- a/Shared/Scene.cs
+++ b/Shared/Scene.cs
@@ -4,6 +4,8 @@ using System;
 
 namespace SemiColinGames {
   class Scene : IDisposable {
+    const float DESIRED_ASPECT_RATIO = 1920.0f / 1080.0f;
+
     public bool Enabled = false;
 
     Color backgroundColor = Color.CornflowerBlue;
@@ -92,13 +94,28 @@ namespace SemiColinGames {
       // Draw debug rects & lines on top.
       Debug.Draw(graphics, basicEffect);
 
-      // Draw sceneTarget to screen.
+      // Get ready to draw sceneTarget to screen.
       graphics.SetRenderTarget(null);
+
+      // Letterbox the scene if needed.
+      float aspectRatio = 1.0f * graphics.Viewport.Width / graphics.Viewport.Height;
+      Rectangle drawRect;
+      if (aspectRatio > DESIRED_ASPECT_RATIO) {
+        // Need to letterbox the sides.
+        int desiredWidth = (int) (graphics.Viewport.Height * DESIRED_ASPECT_RATIO);
+        int padding = (graphics.Viewport.Width - desiredWidth) / 2;
+        drawRect = new Rectangle(padding, 0, desiredWidth, graphics.Viewport.Height);
+      } else {
+        // Need to letterbox the top / bottom.
+        int desiredHeight = (int) (graphics.Viewport.Width / DESIRED_ASPECT_RATIO);
+        int padding = (graphics.Viewport.Height - desiredHeight) / 2;
+        drawRect = new Rectangle(0, padding, graphics.Viewport.Width, desiredHeight);
+      }
+
+      // Actually draw to screen.
       spriteBatch.Begin(SpriteSortMode.Immediate, BlendState.AlphaBlend,
           SamplerState.PointClamp, DepthStencilState.Default,
           RasterizerState.CullNone);
-      Rectangle drawRect = new Rectangle(
-        0, 0, graphics.Viewport.Width, graphics.Viewport.Height);
       spriteBatch.Draw(sceneTarget, drawRect, Color.White);
 
       // Draw debug toasts.