Heuristic to detect if a gamecube game is rendering 16:9 widescreen.

Someone suggested on IRC that we should make a database of memory
locations in GameCube games which contain the 'Widescreen' setting
so we can automatically detect if the game is in 4:3 or 16:9 mode.

But that's hardly optimal, when the game actually tells the gpu
what aspect ratio to render in. 10 min and 6 lines of code later,
this is the result. Not only does it detect the correct aspect ratio
it does so on the fly.

I'm a little suprised nobody thought about doing this before.

1 files changed, 17 insertions, 0 deletions

diff --git a/Source/Core/VideoCommon/VertexShaderManager.cpp b/Source/Core/VideoCommon/VertexShaderManager.cpp
index 509974c373..a6bab1aabf 100644
--- a/Source/Core/VideoCommon/VertexShaderManager.cpp
+++ b/Source/Core/VideoCommon/VertexShaderManager.cpp
@@ -9,6 +9,8 @@
 #include "Common/BitSet.h"
 #include "Common/CommonTypes.h"
 #include "Common/MathUtil.h"
+#include "Core/ConfigManager.h"
+#include "Core/Core.h"
 #include "VideoCommon/BPMemory.h"
 #include "VideoCommon/CPMemory.h"
 #include "VideoCommon/RenderBase.h"
@@ -417,6 +419,21 @@ void VertexShaderManager::SetConstants()
 			g_fProjectionMatrix[14] = -1.0f;
 			g_fProjectionMatrix[15] = 0.0f;
 
+			// Heuristic to detect if a GameCube game is in 16:9 anamorphic widescreen mode.
+			if (!SConfig::GetInstance().bWii)
+			{
+				// Due to the BT.601 standard which the GameCube is based on being a compromise
+				// between PAL and NTSC, neither standard gets square pixels. They are each off
+				// by ~9% in opposite directions.
+				// Just in case any game decides to take this into account, we do these tests
+				// with a large amount of slop.
+				float aspect = fabsf(rawProjection[2] / rawProjection[0]);
+				if (fabsf(aspect - 16.0f/9.0f) < 16.0f/9.0f * 0.11) // within 11% of 16:9
+					g_aspect_wide = true;
+				else if (fabsf(aspect - 4.0f/3.0f) < 4.0f/3.0f * 0.11) // within 11% of 4:3
+					g_aspect_wide = false;
+			}
+
 			SETSTAT_FT(stats.gproj_0,  g_fProjectionMatrix[0]);
 			SETSTAT_FT(stats.gproj_1,  g_fProjectionMatrix[1]);
 			SETSTAT_FT(stats.gproj_2,  g_fProjectionMatrix[2]);