OpenGL: cleanup yuv2rgb (real xfb) workflow

We neither scale nor render from subimages, so we by using gl_Position, we don't have to generate _any_ vertices for this converting.

Also remove the glTexSubImage optimization as every driver does it when needed. But there are some workflows (eg on APU) where it's better to realloc this texture instead of a second memcpy or stall.

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

@@ -28,8 +28,6 @@ using OGL::TextureCache;
 
 static GLuint s_texConvFrameBuffer = 0;
 static GLuint s_srcTexture = 0;			// for decoding from RAM
-static GLuint s_srcTextureWidth = 0;
-static GLuint s_srcTextureHeight = 0;
 static GLuint s_dstTexture = 0;		// for encoding to RAM
 
 const int renderBufferWidth = 1024;
@@ -44,11 +42,8 @@ static SHADER s_encodingPrograms[NUM_ENCODING_PROGRAMS];
 
 static GLuint s_encode_VBO = 0;
 static GLuint s_encode_VAO = 0;
-static GLuint s_decode_VBO = 0;
 static GLuint s_decode_VAO = 0;
 static TargetRectangle s_cached_sourceRc;
-static int s_cached_srcWidth = 0;
-static int s_cached_srcHeight = 0;
 
 static const char *VProgram =
 	"ATTRIN vec2 rawpos;\n"
@@ -102,19 +97,28 @@ void CreatePrograms()
 	 * same algorithm as the flipper, and could result in slight colour inaccuracies
 	 * when run back through this shader.
 	 */
+	const char *VProgramYuyvToRgb =
+		"void main()\n"
+		"{\n"
+		"	vec2 rawpos = vec2(gl_VertexID&1, gl_VertexID&2);\n"
+		"	gl_Position = vec4(rawpos*2.0-1.0, 0.0, 1.0);\n"
+		"}\n";
 	const char *FProgramYuyvToRgb =
 		"uniform sampler2DRect samp9;\n"
 		"VARYIN vec2 uv0;\n"
 		"COLOROUT(ocol0)\n"
 		"void main()\n"
 		"{\n"
+		"	ivec2 uv = ivec2(gl_FragCoord.xy);\n"
 #ifdef USE_GLES3
-		"	vec4 c0 = texelFetch(samp9, ivec2(uv0), 0);\n"
+			// We switch top/bottom here. TODO: move this to screen blit.
+		"	ivec2 ts = textureSize(samp9, 0);\n"
+		"	vec4 c0 = texelFetch(samp9, ivec2(uv.x/2, ts.y-uv.y-1), 0);\n"
 #else
-		"	vec4 c0 = texelFetch(samp9, ivec2(uv0));\n"
+		"	ivec2 ts = textureSize(samp9);\n"
+		"	vec4 c0 = texelFetch(samp9, ivec2(uv.x/2, ts.y-uv.y-1));\n"
 #endif
-		"	float f = step(0.5, fract(uv0.x));\n"
-		"	float y = mix(c0.b, c0.r, f);\n"
+		"	float y = mix(c0.b, c0.r, uv.x & 1);\n"
 		"	float yComp = 1.164 * (y - 0.0625);\n"
 		"	float uComp = c0.g - 0.5;\n"
 		"	float vComp = c0.a - 0.5;\n"
@@ -125,7 +129,7 @@ void CreatePrograms()
 		"}\n";
 
 	ProgramShaderCache::CompileShader(s_rgbToYuyvProgram, VProgram, FProgramRgbToYuyv);
-	ProgramShaderCache::CompileShader(s_yuyvToRgbProgram, VProgram, FProgramYuyvToRgb);
+	ProgramShaderCache::CompileShader(s_yuyvToRgbProgram, VProgramYuyvToRgb, FProgramYuyvToRgb);
 }
 
 SHADER &GetOrCreateEncodingShader(u32 format)
@@ -173,19 +177,8 @@ void Init()
 	s_cached_sourceRc.left = -1;
 	s_cached_sourceRc.right = -1;
 
-	glGenBuffers(1, &s_decode_VBO );
 	glGenVertexArrays(1, &s_decode_VAO );
-	glBindBuffer(GL_ARRAY_BUFFER, s_decode_VBO );
 	glBindVertexArray( s_decode_VAO );
-	s_cached_srcWidth = -1;
-	s_cached_srcHeight = -1;
-	glEnableVertexAttribArray(SHADER_POSITION_ATTRIB);
-	glVertexAttribPointer(SHADER_POSITION_ATTRIB, 2, GL_FLOAT, 0, sizeof(GLfloat)*4, (GLfloat*)NULL);
-	glEnableVertexAttribArray(SHADER_TEXTURE0_ATTRIB);
-	glVertexAttribPointer(SHADER_TEXTURE0_ATTRIB, 2, GL_FLOAT, 0, sizeof(GLfloat)*4, (GLfloat*)NULL+2);
-
-	s_srcTextureWidth = 0;
-	s_srcTextureHeight = 0;
 
 	glActiveTexture(GL_TEXTURE0 + 9);
 	glGenTextures(1, &s_srcTexture);
@@ -207,7 +200,6 @@ void Shutdown()
 	glDeleteFramebuffers(1, &s_texConvFrameBuffer);
 	glDeleteBuffers(1, &s_encode_VBO );
 	glDeleteVertexArrays(1, &s_encode_VAO );
-	glDeleteBuffers(1, &s_decode_VBO );
 	glDeleteVertexArrays(1, &s_decode_VAO );
 
 	s_rgbToYuyvProgram.Destroy();
@@ -395,8 +387,6 @@ void DecodeToTexture(u32 xfbAddr, int srcWidth, int srcHeight, GLuint destTextur
 		return;
 	}
 
-	int srcFmtWidth = srcWidth / 2;
-
 	g_renderer->ResetAPIState(); // reset any game specific settings
 
 	// switch to texture converter frame buffer
@@ -410,50 +400,14 @@ void DecodeToTexture(u32 xfbAddr, int srcWidth, int srcHeight, GLuint destTextur
 	// set srcAddr as data for source texture
 	glActiveTexture(GL_TEXTURE0+9);
 	glBindTexture(getFbType(), s_srcTexture);
-
-	// TODO: make this less slow.  (How?)
-	if ((GLsizei)s_srcTextureWidth == (GLsizei)srcFmtWidth && (GLsizei)s_srcTextureHeight == (GLsizei)srcHeight)
-	{
-		glTexSubImage2D(getFbType(), 0,0,0,s_srcTextureWidth, s_srcTextureHeight,
-				GL_BGRA, GL_UNSIGNED_BYTE, srcAddr);
-	}
-	else
-	{
-		glTexImage2D(getFbType(), 0, GL_RGBA, (GLsizei)srcFmtWidth, (GLsizei)srcHeight,
-				0, GL_BGRA, GL_UNSIGNED_BYTE, srcAddr);
-		s_srcTextureWidth = (GLsizei)srcFmtWidth;
-		s_srcTextureHeight = (GLsizei)srcHeight;
-	}
+	glTexImage2D(getFbType(), 0, GL_RGBA, srcWidth / 2, srcHeight, 0, GL_BGRA, GL_UNSIGNED_BYTE, srcAddr);
 
 	glViewport(0, 0, srcWidth, srcHeight);
 	s_yuyvToRgbProgram.Bind();
 
-	GL_REPORT_ERRORD();
-
-	if(s_cached_srcHeight != srcHeight || s_cached_srcWidth != srcWidth) {
-		GLfloat vertices[] = {
-			1.f, -1.f,
-			(float)srcFmtWidth, (float)srcHeight,
-			1.f, 1.f,
-			(float)srcFmtWidth, 0.f,
-			-1.f, -1.f,
-			0.f, (float)srcHeight,
-			-1.f, 1.f,
-			0.f, 0.f
-		};
-
-		glBindBuffer(GL_ARRAY_BUFFER, s_decode_VBO );
-		glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat)*4*4, vertices, GL_STREAM_DRAW);
-
-		s_cached_srcHeight = srcHeight;
-		s_cached_srcWidth = srcWidth;
-	}
-
 	glBindVertexArray( s_decode_VAO );
 	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
 
-	GL_REPORT_ERRORD();
-
 	FramebufferManager::SetFramebuffer(0);
 
 	g_renderer->RestoreAPIState();