From b6e91aef32ff5c737f73872899b187c7770236c5 Mon Sep 17 00:00:00 2001
From: alyosha-tas <alexei.f.k@gmail.com>
Date: Mon, 2 Aug 2021 11:44:11 -0400
Subject: [PATCH] SMS: make undrawn area black, overscan itelf still needs
 reworking, fixes #2892

---
 .../Consoles/Sega/SMS/VDP.Mode4.cs                    | 11 +++++++----
 src/BizHawk.Emulation.Cores/Consoles/Sega/SMS/VDP.cs  |  2 +-
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/BizHawk.Emulation.Cores/Consoles/Sega/SMS/VDP.Mode4.cs b/src/BizHawk.Emulation.Cores/Consoles/Sega/SMS/VDP.Mode4.cs
index b05fca6047..bb6b8c63e3 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Sega/SMS/VDP.Mode4.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Sega/SMS/VDP.Mode4.cs
@@ -304,25 +304,28 @@ namespace BizHawk.Emulation.Cores.Sega.MasterSystem
 				OverscanFrameBuffer = new int[OverscanFrameHeight * OverscanFrameWidth];
 			}
 
+			// TODO: overscan color can change, this should be calculated per scanline, not done in bulk at the end
+			int overscan_color = Palette[BackdropColor];
+
 			// Top overscan
 			for (int y=0; y<overscanTop; y++)
 				for (int x = 0; x < OverscanFrameWidth; x++)
-					OverscanFrameBuffer[(y * OverscanFrameWidth) + x] = BackgroundColor;
+					OverscanFrameBuffer[(y * OverscanFrameWidth) + x] = overscan_color;
 			
 			// Bottom overscan
 			for (int y = overscanTop + 192; y < OverscanFrameHeight; y++)
 				for (int x = 0; x < OverscanFrameWidth; x++)
-					OverscanFrameBuffer[(y * OverscanFrameWidth) + x] = BackgroundColor;
+					OverscanFrameBuffer[(y * OverscanFrameWidth) + x] = overscan_color;
 
 			// Left overscan
 			for (int y = overscanTop; y < overscanTop + 192; y++)
 				for (int x = 0; x < overscanLeft; x++)
-					OverscanFrameBuffer[(y * OverscanFrameWidth) + x] = BackgroundColor;
+					OverscanFrameBuffer[(y * OverscanFrameWidth) + x] = overscan_color;
 
 			// Right overscan
 			for (int y = overscanTop; y < overscanTop + 192; y++)
 				for (int x = overscanLeft + 256; x < OverscanFrameWidth; x++)
-					OverscanFrameBuffer[(y * OverscanFrameWidth) + x] = BackgroundColor;
+					OverscanFrameBuffer[(y * OverscanFrameWidth) + x] = overscan_color;
 
 			// Active display area
 			for (int y = 0; y < 192; y++)
diff --git a/src/BizHawk.Emulation.Cores/Consoles/Sega/SMS/VDP.cs b/src/BizHawk.Emulation.Cores/Consoles/Sega/SMS/VDP.cs
index f251c76ae2..102ed0d0c2 100644
--- a/src/BizHawk.Emulation.Cores/Consoles/Sega/SMS/VDP.cs
+++ b/src/BizHawk.Emulation.Cores/Consoles/Sega/SMS/VDP.cs
@@ -473,7 +473,7 @@ namespace BizHawk.Emulation.Cores.Sega.MasterSystem
 			}
 		}
 
-		public int BackgroundColor => Palette[BackdropColor];
+		public int BackgroundColor => unchecked((int)0xFF000000);
 
 		public int VsyncNumerator => DisplayType == DisplayType.NTSC ? 60 : 50;