Sketched out a quick class for rendering to texture.

OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj

@@ -15,6 +15,7 @@
 		4B14145E1B5887AA00E04248 /* CPU6502AllRAM.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B1414591B58879D00E04248 /* CPU6502AllRAM.cpp */; };
 		4B1414601B58885000E04248 /* WolfgangLorenzTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4B14145F1B58885000E04248 /* WolfgangLorenzTests.swift */; };
 		4B1414621B58888700E04248 /* KlausDormannTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4B1414611B58888700E04248 /* KlausDormannTests.swift */; };
+		4B2039941C67E20B001375C3 /* TextureTarget.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B2039921C67E20B001375C3 /* TextureTarget.cpp */; };
 		4B2409551C45AB05004DA684 /* Speaker.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B2409531C45AB05004DA684 /* Speaker.cpp */; };
 		4B2E2D951C399D1200138695 /* ElectronDocument.xib in Resources */ = {isa = PBXBuildFile; fileRef = 4B2E2D931C399D1200138695 /* ElectronDocument.xib */; };
 		4B2E2D9A1C3A06EC00138695 /* Atari2600.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 4B2E2D971C3A06EC00138695 /* Atari2600.cpp */; };
@@ -340,6 +341,9 @@
 		4B14145A1B58879D00E04248 /* CPU6502AllRAM.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = CPU6502AllRAM.hpp; sourceTree = "<group>"; };
 		4B14145F1B58885000E04248 /* WolfgangLorenzTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = WolfgangLorenzTests.swift; sourceTree = "<group>"; };
 		4B1414611B58888700E04248 /* KlausDormannTests.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = KlausDormannTests.swift; sourceTree = "<group>"; };
+		4B2039921C67E20B001375C3 /* TextureTarget.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = TextureTarget.cpp; sourceTree = "<group>"; };
+		4B2039931C67E20B001375C3 /* TextureTarget.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = TextureTarget.hpp; sourceTree = "<group>"; };
+		4B2039951C67E2A3001375C3 /* OpenGL.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = OpenGL.h; sourceTree = "<group>"; };
 		4B2409531C45AB05004DA684 /* Speaker.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = Speaker.cpp; path = ../../Outputs/Speaker.cpp; sourceTree = "<group>"; };
 		4B2409541C45AB05004DA684 /* Speaker.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = Speaker.hpp; path = ../../Outputs/Speaker.hpp; sourceTree = "<group>"; };
 		4B24095A1C45DF85004DA684 /* Stepper.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = Stepper.hpp; sourceTree = "<group>"; };
@@ -690,6 +694,9 @@
 				4B0CCC441C62D0B3001CAC5F /* CRTFrame.h */,
 				4B0CCC461C62D1A8001CAC5F /* CRTOpenGL.cpp */,
 				4B7BFEFD1C6446EF00089C1C /* CRTFrameBuilder.cpp */,
+				4B2039921C67E20B001375C3 /* TextureTarget.cpp */,
+				4B2039931C67E20B001375C3 /* TextureTarget.hpp */,
+				4B2039951C67E2A3001375C3 /* OpenGL.h */,
 			);
 			name = CRT;
 			path = ../../Outputs/CRT;
@@ -1608,6 +1615,7 @@
 				4B55CE4B1C3B3B0C0093A61B /* CSAtari2600.mm in Sources */,
 				4B55CE581C3B7D360093A61B /* Atari2600Document.swift in Sources */,
 				4B0CCC471C62D1A8001CAC5F /* CRTOpenGL.cpp in Sources */,
+				4B2039941C67E20B001375C3 /* TextureTarget.cpp in Sources */,
 				4B0EBFB81C487F2F00A11F35 /* AudioQueue.m in Sources */,
 				4B7BFEFE1C6446EF00089C1C /* CRTFrameBuilder.cpp in Sources */,
 				4B55CE5F1C3B7D960093A61B /* MachineDocument.swift in Sources */,

Outputs/CRT/CRTOpenGL.cpp

@@ -9,9 +9,7 @@
 #include "CRT.hpp"
 #include <stdlib.h>
 
-// TODO: figure out correct include paths for other platforms.
+#include "OpenGL.h"
-#include <OpenGL/OpenGL.h>
-#include <OpenGL/gl3.h>
 
 using namespace Outputs;
 
@@ -90,6 +88,9 @@ void CRT::draw_frame(int output_width, int output_height, bool only_if_dirty)
 {
 	_current_frame_mutex->lock();
 
+	GLint defaultFramebuffer;
+	glGetIntegerv(GL_FRAMEBUFFER_BINDING, &defaultFramebuffer);
+
 	if(!_current_frame && !only_if_dirty)
 	{
 		glClear(GL_COLOR_BUFFER_BIT);

Outputs/CRT/OpenGL.h

@@ -0,0 +1,16 @@
+//
+//  OpenGL.h
+//  Clock Signal
+//
+//  Created by Thomas Harte on 07/02/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#ifndef OpenGL_h
+#define OpenGL_h
+
+// TODO: figure out correct include paths for other platforms.
+#include <OpenGL/OpenGL.h>
+#include <OpenGL/gl3.h>
+
+#endif /* OpenGL_h */

Outputs/CRT/TextureTarget.cpp

@@ -0,0 +1,46 @@
+//
+//  TextureTarget.cpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 07/02/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#include "TextureTarget.hpp"
+
+using namespace OpenGL;
+
+TextureTarget::TextureTarget(unsigned int width, unsigned int height)
+{
+	glGenFramebuffers(1, &_framebuffer);
+	glBindFramebuffer(GL_FRAMEBUFFER, _framebuffer);
+
+	glGenTextures(1, &_texture);
+	glBindTexture(GL_TEXTURE_2D, _texture);
+
+	uint8_t *emptySpace = new uint8_t[width*height*4];
+	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, (GLsizei)width, (GLsizei)height, 0, GL_RGBA, GL_UNSIGNED_BYTE, emptySpace);
+	delete[] emptySpace;
+
+	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, _texture, 0);
+
+	// TODO: raise an exception if check framebuffer status fails.
+//		if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
+//			return nil;
+}
+
+TextureTarget::~TextureTarget()
+{
+	glDeleteFramebuffers(1, &_framebuffer);
+	glDeleteTextures(1, &_texture);
+}
+
+void TextureTarget::bind_framebuffer()
+{
+	glBindFramebuffer(GL_FRAMEBUFFER, _framebuffer);
+}
+
+void TextureTarget::bind_texture()
+{
+	glBindTexture(GL_TEXTURE_2D, _texture);
+}

Outputs/CRT/TextureTarget.hpp

@@ -0,0 +1,30 @@
+//
+//  TextureTarget.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 07/02/2016.
+//  Copyright © 2016 Thomas Harte. All rights reserved.
+//
+
+#ifndef TextureTarget_hpp
+#define TextureTarget_hpp
+
+#include "OpenGL.h"
+
+namespace OpenGL {
+
+class TextureTarget {
+	public:
+		TextureTarget(unsigned int width, unsigned int height);
+		~TextureTarget();
+
+		void bind_framebuffer();
+		void bind_texture();
+
+	private:
+		GLuint _framebuffer, _texture;
+};
+
+}
+
+#endif /* TextureTarget_hpp */