Fixed default color values for R and RG types

By default, in D3D, R, G or B channels default to 1 when no
value is assigned to them. In OpenGL, these channels default
to 0. Added an entry to Conventions to fix this issue.

In dEQP, this fixes all R and RG types tests from:
functional.texture.format.*

Change-Id: Ib5552aa36eaf4e3e1132f016f002250b40436227
Reviewed-on: https://swiftshader-review.googlesource.com/10828
Tested-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>

src/Renderer/Context.cpp

diff --git a/src/Renderer/Context.cpp b/src/Renderer/Context.cpp
index caa4592..e5ee4dc 100644
--- a/src/Renderer/Context.cpp
+++ b/src/Renderer/Context.cpp
@@ -33,6 +33,7 @@
 	bool fullPixelPositionRegister = false;
 	bool leadingVertexFirst = false;         // Flat shading uses first vertex, else last
 	bool secondaryColor = false;             // Specular lighting is applied after texturing
+	bool colorsDefaultToZero = false;
 
 	bool forceWindowed = false;
 	bool quadLayoutEnabled = false;

src/Renderer/Renderer.cpp

diff --git a/src/Renderer/Renderer.cpp b/src/Renderer/Renderer.cpp
index a67ba22..7afbb9f 100644
--- a/src/Renderer/Renderer.cpp
+++ b/src/Renderer/Renderer.cpp
@@ -48,6 +48,7 @@
 	extern bool fullPixelPositionRegister;
 	extern bool leadingVertexFirst;         // Flat shading uses first vertex, else last
 	extern bool secondaryColor;             // Specular lighting is applied after texturing
+	extern bool colorsDefaultToZero;
 
 	extern bool forceWindowed;
 	extern bool complementaryDepthBuffer;
@@ -110,6 +111,7 @@
 		sw::fullPixelPositionRegister = conventions.fullPixelPositionRegister;
 		sw::leadingVertexFirst = conventions.leadingVertexFirst;
 		sw::secondaryColor = conventions.secondaryColor;
+		sw::colorsDefaultToZero = conventions.colorsDefaultToZero;
 		sw::exactColorRounding = exactColorRounding;
 
 		setRenderTarget(0, 0);

src/Renderer/Renderer.hpp

diff --git a/src/Renderer/Renderer.hpp b/src/Renderer/Renderer.hpp
index c29020f..dedd17a 100644
--- a/src/Renderer/Renderer.hpp
+++ b/src/Renderer/Renderer.hpp
@@ -65,6 +65,7 @@
 		bool fullPixelPositionRegister;
 		bool leadingVertexFirst;
 		bool secondaryColor;
+		bool colorsDefaultToZero;
 	};
 
 	static const Conventions OpenGL =
@@ -74,7 +75,8 @@
 		true,    // booleanFaceRegister
 		true,    // fullPixelPositionRegister
 		false,   // leadingVertexFirst
-		false    // secondaryColor
+		false,   // secondaryColor
+		true,    // colorsDefaultToZero
 	};
 
 	static const Conventions Direct3D =
@@ -85,6 +87,7 @@
 		false,   // fullPixelPositionRegister
 		true,    // leadingVertexFirst
 		true,    // secondardyColor
+		false,   // colorsDefaultToZero
 	};
 
 	struct Query

src/Shader/SamplerCore.cpp

diff --git a/src/Shader/SamplerCore.cpp b/src/Shader/SamplerCore.cpp
index f0d482f..0ee9014 100644
--- a/src/Shader/SamplerCore.cpp
+++ b/src/Shader/SamplerCore.cpp
@@ -50,6 +50,8 @@
 
 namespace sw
 {
+	extern bool colorsDefaultToZero;
+
 	SamplerCore::SamplerCore(Pointer<Byte> &constants, const Sampler::State &state) : constants(constants), state(state)
 	{
 	}
@@ -186,6 +188,7 @@
 			if(fixed12 && state.textureFilter != FILTER_GATHER)
 			{
 				int componentCount = textureComponentCount();
+				short defaultColorValue = colorsDefaultToZero ? 0x0000 : 0x1000;
 
 				switch(state.textureFormat)
 				{
@@ -237,8 +240,8 @@
 				case FORMAT_YV12_BT601:
 				case FORMAT_YV12_BT709:
 				case FORMAT_YV12_JFIF:
-					if(componentCount < 2) c.y = Short4(0x1000);
-					if(componentCount < 3) c.z = Short4(0x1000);
+					if(componentCount < 2) c.y = Short4(defaultColorValue);
+					if(componentCount < 3) c.z = Short4(defaultColorValue);
 					if(componentCount < 4) c.w = Short4(0x1000);
 					break;
 				case FORMAT_A8:
@@ -259,9 +262,9 @@
 					c.z = c.x;
 					break;
 				case FORMAT_R32F:
-					c.y = Short4(0x1000);
+					c.y = Short4(defaultColorValue);
 				case FORMAT_G32R32F:
-					c.z = Short4(0x1000);
+					c.z = Short4(defaultColorValue);
 				case FORMAT_X32B32G32R32F:
 					c.w = Short4(0x1000);
 				case FORMAT_A32B32G32R32F:
@@ -438,6 +441,7 @@
 			}
 
 			int componentCount = textureComponentCount();
+			float defaultColorValue = colorsDefaultToZero ? 0.0f : 1.0f;
 
 			if(state.textureFilter != FILTER_GATHER)
 			{
@@ -495,8 +499,8 @@
 				case FORMAT_YV12_BT601:
 				case FORMAT_YV12_BT709:
 				case FORMAT_YV12_JFIF:
-					if(componentCount < 2) c.y = Float4(1.0f);
-					if(componentCount < 3) c.z = Float4(1.0f);
+					if(componentCount < 2) c.y = Float4(defaultColorValue);
+					if(componentCount < 3) c.z = Float4(defaultColorValue);
 					if(componentCount < 4) c.w = Float4(1.0f);
 					break;
 				case FORMAT_A8:
@@ -517,9 +521,9 @@
 					c.z = c.x;
 					break;
 				case FORMAT_R32F:
-					c.y = Float4(1.0f);
+					c.y = Float4(defaultColorValue);
 				case FORMAT_G32R32F:
-					c.z = Float4(1.0f);
+					c.z = Float4(defaultColorValue);
 				case FORMAT_X32B32G32R32F:
 					c.w = Float4(1.0f);
 				case FORMAT_A32B32G32R32F: