From 736484548ea021452415a1711aab10e04b521451 Mon Sep 17 00:00:00 2001
From: Nebuleon Fumika
Date: Thu, 10 Jan 2013 18:01:32 -0500
Subject: Attempt to optimise the ADD background drawing mode so it's playable
 on automatic frameskip in games like Super Metroid. It doesn't work well.

See the video for this bug at <http://www.youtube.com/watch?v=sUWjVxAD9Q8>.
---
 source/gfx.cpp | 97 +++++++++++++++++++++++++++-------------------------------
 1 file changed, 45 insertions(+), 52 deletions(-)

(limited to 'source/gfx.cpp')

diff --git a/source/gfx.cpp b/source/gfx.cpp
index f6a6217..decd195 100644
--- a/source/gfx.cpp
+++ b/source/gfx.cpp
@@ -892,8 +892,8 @@ void S9xSetInfoString (const char *string)
 
 inline void SelectTileRenderer (bool8 normal)
 {
-    if (normal)
-    {
+	if (normal)
+	{
 		if (IPPU.HalfWidthPixels)
 		{
 			DrawTilePtr = DrawTile16HalfWidth;
@@ -906,58 +906,51 @@ inline void SelectTileRenderer (bool8 normal)
 			DrawClippedTilePtr = DrawClippedTile16;
 			DrawLargePixelPtr = DrawLargePixel16;
 		}
-    }
-    else
-    {
-		if (GFX.r2131 & 0x80)
-		{
-		    if (GFX.r2131 & 0x40)
-		    {
-				if (GFX.r2130 & 2)
-				{
-				    DrawTilePtr = DrawTile16Sub1_2;
-				    DrawClippedTilePtr = DrawClippedTile16Sub1_2;
-				}
-				else
-				{
-				    // Fixed colour substraction
-				    DrawTilePtr = DrawTile16FixedSub1_2;
-				    DrawClippedTilePtr = DrawClippedTile16FixedSub1_2;
-				}
-				DrawLargePixelPtr = DrawLargePixel16Sub1_2;
-		    }
-		    else
-		    {
-				DrawTilePtr = DrawTile16Sub;
-				DrawClippedTilePtr = DrawClippedTile16Sub;
-				DrawLargePixelPtr = DrawLargePixel16Sub;
-		    }
-		}
-		else
+	}
+	else
+	{
+		switch (GFX.r2131 & 0xC0)
 		{
-		    if (GFX.r2131 & 0x40)
-		    {
-				if (GFX.r2130 & 2)
-				{
-				    DrawTilePtr = DrawTile16Add1_2;
-				    DrawClippedTilePtr = DrawClippedTile16Add1_2;
-				}
-				else
-				{
-				    // Fixed colour addition
-				    DrawTilePtr = DrawTile16FixedAdd1_2;
-				    DrawClippedTilePtr = DrawClippedTile16FixedAdd1_2;
-				}
-				DrawLargePixelPtr = DrawLargePixel16Add1_2;
-		    }
-		    else
-		    {
-				DrawTilePtr = DrawTile16Add;
-				DrawClippedTilePtr = DrawClippedTile16Add;
-				DrawLargePixelPtr = DrawLargePixel16Add;
-		    }
+		case 0x00:
+			DrawTilePtr = DrawTile16Add;
+			DrawClippedTilePtr = DrawClippedTile16Add;
+			DrawLargePixelPtr = DrawLargePixel16Add;
+			break;
+		case 0x40:
+			if (GFX.r2130 & 2)
+			{
+				DrawTilePtr = DrawTile16Add1_2;
+				DrawClippedTilePtr = DrawClippedTile16Add1_2;
+			}
+			else
+			{
+				// Fixed colour addition
+				DrawTilePtr = DrawTile16FixedAdd1_2;
+				DrawClippedTilePtr = DrawClippedTile16FixedAdd1_2;
+			}
+			DrawLargePixelPtr = DrawLargePixel16Add1_2;
+			break;
+		case 0x80:
+			DrawTilePtr = DrawTile16Sub;
+			DrawClippedTilePtr = DrawClippedTile16Sub;
+			DrawLargePixelPtr = DrawLargePixel16Sub;
+			break;
+		case 0xC0:
+			if (GFX.r2130 & 2)
+			{
+				DrawTilePtr = DrawTile16Sub1_2;
+				DrawClippedTilePtr = DrawClippedTile16Sub1_2;
+			}
+			else
+			{
+				// Fixed colour substraction
+				DrawTilePtr = DrawTile16FixedSub1_2;
+				DrawClippedTilePtr = DrawClippedTile16FixedSub1_2;
+			}
+			DrawLargePixelPtr = DrawLargePixel16Sub1_2;
+			break;
 		}
-    }
+	}
 }
 
 void S9xSetupOBJ ()
-- 
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