VideoCommon: move ViewportCorrection into VideoCommon

D3D doesn't allow bigger viewports than rendertargets. But flipper does, so the viewport will be clipped and the transformation matrix will be changed.
This was done in the D3D backend itself. This is now moved into VideoCommon. This don't reduce code, but in this way, VideoCommon doesn't depend on the backends.

Source/Core/VideoBackends/D3D/Src/Render.cpp

@@ -477,30 +477,9 @@ u32 Renderer::AccessEFB(EFBAccessType type, u32 x, u32 y, u32 poke_data)
 	}
 }
 
-// Viewport correction:
-// Say you want a viewport at (ix, iy) with size (iw, ih),
-// but your viewport must be clamped at (ax, ay) with size (aw, ah).
-// Just multiply the projection matrix with the following to get the same
-// effect:
-// [   (iw/aw)         0     0    ((iw - 2*(ax-ix)) / aw - 1)   ]
-// [         0   (ih/ah)     0   ((-ih + 2*(ay-iy)) / ah + 1)   ]
-// [         0         0     1                              0   ]
-// [         0         0     0                              1   ]
-static void ViewportCorrectionMatrix(Matrix44& result,
-	float ix, float iy, float iw, float ih, // Intended viewport (x, y, width, height)
-	float ax, float ay, float aw, float ah) // Actual viewport (x, y, width, height)
-{
-	Matrix44::LoadIdentity(result);
-	if (aw == 0.f || ah == 0.f)
-		return;
-	result.data[4*0+0] = iw / aw;
-	result.data[4*0+3] = (iw - 2.f * (ax - ix)) / aw - 1.f;
-	result.data[4*1+1] = ih / ah;
-	result.data[4*1+3] = (-ih + 2.f * (ay - iy)) / ah + 1.f;
-}
 
 // Called from VertexShaderManager
-void Renderer::UpdateViewport(Matrix44& vpCorrection)
+void Renderer::UpdateViewport()
 {
 	// reversed gxsetviewport(xorig, yorig, width, height, nearz, farz)
 	// [0] = width/2
@@ -513,34 +492,26 @@ void Renderer::UpdateViewport(Matrix44& vpCorrection)
 	int scissorXOff = bpmem.scissorOffset.x * 2;
 	int scissorYOff = bpmem.scissorOffset.y * 2;
 
-	float intendedX = Renderer::EFBToScaledXf(xfregs.viewport.xOrig - xfregs.viewport.wd - scissorXOff);
-	float intendedY = Renderer::EFBToScaledYf(xfregs.viewport.yOrig + xfregs.viewport.ht - scissorYOff);
-	float intendedWd = Renderer::EFBToScaledXf(2.0f * xfregs.viewport.wd);
-	float intendedHt = Renderer::EFBToScaledYf(-2.0f * xfregs.viewport.ht);
-	if (intendedWd < 0.f)
+	float X = Renderer::EFBToScaledXf(xfregs.viewport.xOrig - xfregs.viewport.wd - scissorXOff);
+	float Y = Renderer::EFBToScaledYf(xfregs.viewport.yOrig + xfregs.viewport.ht - scissorYOff);
+	float Wd = Renderer::EFBToScaledXf(2.0f * xfregs.viewport.wd);
+	float Ht = Renderer::EFBToScaledYf(-2.0f * xfregs.viewport.ht);
+	if (Wd < 0.0f)
 	{
-		intendedX += intendedWd;
-		intendedWd = -intendedWd;
+		X += Wd;
+		Wd = -Wd;
 	}
-	if (intendedHt < 0.f)
+	if (Ht < 0.0f)
 	{
-		intendedY += intendedHt;
-		intendedHt = -intendedHt;
+		Y += Ht;
+		Ht = -Ht;
 	}
 
 	// In D3D, the viewport rectangle must fit within the render target.
-	float X = (intendedX >= 0.f) ? intendedX : 0.f;
-	float Y = (intendedY >= 0.f) ? intendedY : 0.f;
-	float Wd = (X + intendedWd <= GetTargetWidth()) ? intendedWd : (GetTargetWidth() - X);
-	float Ht = (Y + intendedHt <= GetTargetHeight()) ? intendedHt : (GetTargetHeight() - Y);
-
-	// If GX viewport is off the render target, we must clamp our viewport
-	// within the bounds. Use the correction matrix to compensate.
-	ViewportCorrectionMatrix(vpCorrection,
-		intendedX, intendedY,
-		intendedWd, intendedHt,
-		X, Y,
-		Wd, Ht);
+	X = (X >= 0.f) ? X : 0.f;
+	Y = (Y >= 0.f) ? Y : 0.f;
+	Wd = (X + Wd <= GetTargetWidth()) ? Wd : (GetTargetWidth() - X);
+	Ht = (Y + Ht <= GetTargetHeight()) ? Ht : (GetTargetHeight() - Y);
 
 	// Some games set invalid values for z-min and z-max so fix them to the max and min allowed and let the shaders do this work
 	D3D11_VIEWPORT vp = CD3D11_VIEWPORT(X, Y,

Source/Core/VideoBackends/D3D/Src/Render.h

@@ -46,7 +46,7 @@ public:
 
 	void ReinterpretPixelData(unsigned int convtype);
 
-	void UpdateViewport(Matrix44& vpCorrection);
+	void UpdateViewport();
 
 	bool SaveScreenshot(const std::string &filename, const TargetRectangle &rc);
 

Source/Core/VideoBackends/D3D/Src/main.cpp

@@ -90,6 +90,7 @@ void InitBackendInfo()
 	g_Config.backend_info.bSupportsFormatReinterpretation = true;
 	g_Config.backend_info.bSupportsPixelLighting = true;
 	g_Config.backend_info.bSupportsPrimitiveRestart = true;
+	g_Config.backend_info.bSupportsOversizedViewports = false;
 
 	IDXGIFactory* factory;
 	IDXGIAdapter* ad;

Source/Core/VideoBackends/OGL/Src/Render.cpp

@@ -1093,7 +1093,7 @@ u32 Renderer::AccessEFB(EFBAccessType type, u32 x, u32 y, u32 poke_data)
 }
 
 // Called from VertexShaderManager
-void Renderer::UpdateViewport(Matrix44& vpCorrection)
+void Renderer::UpdateViewport()
 {
 	// reversed gxsetviewport(xorig, yorig, width, height, nearz, farz)
 	// [0] = width/2
@@ -1124,9 +1124,6 @@ void Renderer::UpdateViewport(Matrix44& vpCorrection)
 		Height *= -1;
 	}
 
-	// OpenGL does not require any viewport correct
-	Matrix44::LoadIdentity(vpCorrection);
-
 	// Update the view port
 	if(g_ogl_config.bSupportViewportFloat)
 	{

Source/Core/VideoBackends/OGL/Src/Render.h

@@ -78,7 +78,7 @@ public:
 
 	void ReinterpretPixelData(unsigned int convtype);
 
-	void UpdateViewport(Matrix44& vpCorrection);
+	void UpdateViewport();
 
 	bool SaveScreenshot(const std::string &filename, const TargetRectangle &rc);
 

Source/Core/VideoBackends/OGL/Src/main.cpp

@@ -146,6 +146,7 @@ void InitBackendInfo()
 	g_Config.backend_info.bSupportsFormatReinterpretation = true;
 	g_Config.backend_info.bSupportsPixelLighting = true;
 	//g_Config.backend_info.bSupportsEarlyZ = true; // is gpu dependent and must be set in renderer
+	g_Config.backend_info.bSupportsOversizedViewports = true;
 
 	// aamodes
 	const char* caamodes[] = {_trans("None"), "2x", "4x", "8x", "8x CSAA", "8xQ CSAA", "16x CSAA", "16xQ CSAA", "4x SSAA"};