better error check (not tested)

fob has a new ctor (from context and stuff)

J.xcodeproj/project.pbxproj

@@ -9,6 +9,7 @@
 /* Begin PBXBuildFile section */
 		425E9DF2140A74DA00A81A65 /* basic.h in Headers */ = {isa = PBXBuildFile; fileRef = 425E9DF1140A74DA00A81A65 /* basic.h */; };
 		425E9DF6140A774D00A81A65 /* basic.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 425E9DF5140A774D00A81A65 /* basic.cpp */; };
+		425E9DF9140A7EB400A81A65 /* fbo.mm in Sources */ = {isa = PBXBuildFile; fileRef = 425E9DF8140A7EB400A81A65 /* fbo.mm */; };
 		42681369140A321800CBF943 /* Foundation.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 42681368140A321800CBF943 /* Foundation.framework */; };
 		4268136F140A321800CBF943 /* J.mm in Sources */ = {isa = PBXBuildFile; fileRef = 4268136E140A321800CBF943 /* J.mm */; };
 		42ED6A6B140A380000402F76 /* fbo.h in Headers */ = {isa = PBXBuildFile; fileRef = 42ED6A68140A380000402F76 /* fbo.h */; };
@@ -19,6 +20,7 @@
 /* Begin PBXFileReference section */
 		425E9DF1140A74DA00A81A65 /* basic.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = basic.h; sourceTree = "<group>"; };
 		425E9DF5140A774D00A81A65 /* basic.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = basic.cpp; sourceTree = "<group>"; };
+		425E9DF8140A7EB400A81A65 /* fbo.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = fbo.mm; sourceTree = "<group>"; };
 		42681365140A321800CBF943 /* libJ.a */ = {isa = PBXFileReference; explicitFileType = archive.ar; includeInIndex = 0; path = libJ.a; sourceTree = BUILT_PRODUCTS_DIR; };
 		42681368140A321800CBF943 /* Foundation.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = Foundation.framework; path = System/Library/Frameworks/Foundation.framework; sourceTree = SDKROOT; };
 		4268136C140A321800CBF943 /* J-Prefix.pch */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = "J-Prefix.pch"; sourceTree = "<group>"; };
@@ -82,6 +84,7 @@
 				425E9DF1140A74DA00A81A65 /* basic.h */,
 				425E9DF5140A774D00A81A65 /* basic.cpp */,
 				42ED6A68140A380000402F76 /* fbo.h */,
+				425E9DF8140A7EB400A81A65 /* fbo.mm */,
 				42ED6A69140A380000402F76 /* shader.h */,
 				4268136D140A321800CBF943 /* J.h */,
 				4268136E140A321800CBF943 /* J.mm */,
@@ -164,6 +167,7 @@
 			files = (
 				4268136F140A321800CBF943 /* J.mm in Sources */,
 				425E9DF6140A774D00A81A65 /* basic.cpp in Sources */,
+				425E9DF9140A7EB400A81A65 /* fbo.mm in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

J/basic.cpp

@@ -12,8 +12,18 @@ namespace J {
     void check_error(){
         #if defined(DEBUG)
 		GLenum status = glGetError();
-		if(status != GL_NO_ERROR){
-			throw std::runtime_error("GL Error: " + std::to_string(status));
+        switch (status) {
+            case GL_NO_ERROR:
+                return;
+            #define c(x) case x: throw std::runtime_error("GL Error: "#x);
+                c(GL_INVALID_ENUM)
+                c(GL_INVALID_VALUE)
+                c(GL_INVALID_OPERATION)
+                c(GL_INVALID_FRAMEBUFFER_OPERATION)
+                c(GL_OUT_OF_MEMORY)
+            #undef c
+            default:
+                throw std::runtime_error("GL Error: UNKNOWN");
         }
         #endif
 	}

J/fbo.h

@@ -16,6 +16,10 @@
 
 #include "basic.h"
 
+@class EAGLContext;
+@class CAEAGLLayer;
+
+
 // TODO: more error checking in debug build.
 // TODO: make texture class? for easier switching between linear/nearest interpolation for example
 // NOTE: stencil attachment is not supported
@@ -32,6 +36,7 @@ public:
 	GLuint texture_id;
 
 public:
+    // standard ctor, makes use of textures
 	fbo(int width, int height) : width(width), height(height), fbo_number(0), renderbuffers(), texture_id(0) {
 		glGenFramebuffers(1, &fbo_number);
 		bind();
@@ -53,6 +58,10 @@ public:
 
 		unbind();
 	}
+    
+    // ctor from EAGLContext, not using texture, so you cannot use it as lookup, only as renderer.
+    fbo(EAGLContext* context, CAEAGLLayer* layer);
+    
 	~fbo() {
 		end();
 
@@ -60,17 +69,18 @@ public:
 
 		for(RenderbuffersMap::const_iterator i = renderbuffers.begin(); i != renderbuffers.end(); ++i){
             RenderbuffersMap::value_type const & it = *i;
-			glDeleteFramebuffers(1, &it.second);
+			glDeleteRenderbuffers(1, &it.second);
 		}
         
         glDeleteTextures(1, &texture_id);
+        // NOTE: glDeleteTextures silently ignores 0's and names that do not correspond to existing textures.
 	}
 
 	void begin(){
 		bind();
         // FIXME: this should be done, but also switching back should be done...
 		//glPushAttrib(GL_VIEWPORT);
-		//glViewport(0, 0, width, height);
+		glViewport(0, 0, width, height);
 
         // NOTE: commented out, because we don't want fbo's to nest.
 		/*GLint savedFramebuffer = -1;
@@ -80,11 +90,10 @@ public:
 
 	void end(){
 		unbind();
-        // FIXME: switch back to previous viewport.
+        // FIXME: switch back to previous viewport. See begin()
 		//glPopAttrib();
 	}
 
-private:
 	void bind(){
 		glBindFramebuffer(GL_FRAMEBUFFER, fbo_number);
 		check_error();
@@ -94,6 +103,7 @@ private:
 		glBindFramebuffer(GL_FRAMEBUFFER, 0);
 	}
     
+private:
 	void create_attach_renderbuffer(GLenum format, GLenum attachment_point) {
 		GLuint buffer;
 		glGenRenderbuffers(1, &buffer);

J/fbo.mm

@@ -0,0 +1,43 @@
+//
+//  fbo.mm
+//  J
+//
+//  Created by Joshua Moerman on 8/28/11.
+//  Copyright 2011 Vadovas. All rights reserved.
+//
+
+#import "fbo.h"
+
+#import <QuartzCore/QuartzCore.h>
+
+namespace J {
+    fbo::fbo(EAGLContext* context, CAEAGLLayer* layer) : width(0), height(0), fbo_number(0), renderbuffers(), texture_id(0){
+        glGenFramebuffers(1, &fbo_number);
+        bind();
+        
+        // much like create_attach_renderbuffer(), but it's not created, but given by the context.
+        {
+            GLuint buffer;
+            glGenRenderbuffers(1, &buffer);
+            glBindRenderbuffer(GL_RENDERBUFFER, buffer);
+            [context renderbufferStorage:GL_RENDERBUFFER fromDrawable:layer];
+            glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &width);
+            glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &height);
+            
+            glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, buffer);
+            
+            renderbuffers[GL_COLOR_ATTACHMENT0] = buffer;
+        }
+        
+        //this will cause a INVALID_OPERATION in bind().
+		//create_attach_renderbuffer(GL_DEPTH_COMPONENT16, GL_DEPTH_ATTACHMENT);
+        
+        check_error();
+        check_status();
+        
+        glClearColor(0.0, 0.0, 0.0, 0.0);
+		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
+        
+		unbind();
+    }
+}