Added comments, and hacked shader, so its working

J/shader.h

@@ -10,11 +10,18 @@
 #import <OpenGLES/ES2/gl.h>
 #import <OpenGLES/ES2/glext.h>
 
-// TODO: do glValidateProgram, like in the OpenGL template
+// TODO: do glValidateProgram, like in the OpenGL template (see bottom)
 // TODO: add error checking at set_uniforms?
+// TODO: use an uniform map? (benchmark first!)
 
 namespace J {
     
+enum {
+    ATTRIB_VERTEX,
+    ATTRIB_COLOR,
+    NUM_ATTRIBUTES
+};
+
 class shader {
     typedef std::map<GLenum, GLuint> ShaderMap;
     
@@ -43,6 +50,12 @@ public:
 				throw std::runtime_error(fragment_shader_filename + " couldn't be opened");
 			read_shader(fragment_shader, GL_FRAGMENT_SHADER);
 		}
+        {   // TODO: think of a nice way to implement this
+            // Bind attribute locations.
+            // This needs to be done prior to linking.
+            glBindAttribLocation(program, ATTRIB_VERTEX, "position");
+            glBindAttribLocation(program, ATTRIB_COLOR, "color");
+        }
 
 		link_program();
 	}
@@ -54,6 +67,7 @@ public:
 			GLuint shader = it.second;
 			glDetachShader(program, shader);
 			glDeleteShader(shader);
+            // NOTE: If a shader object to be deleted is attached to a program object, it will be flagged for deletion, but it will not be deleted until it is no longer attached to any program object
 		}
 
 		glDeleteProgram(program);
@@ -183,6 +197,31 @@ private:
 #endif
 	}
     
+    /*
+         // Validate program before drawing. This is a good check, but only really necessary in a debug build.
+     - (BOOL)validateProgram:(GLuint)prog
+     {
+     GLint logLength, status;
+     
+     glValidateProgram(prog);
+     glGetProgramiv(prog, GL_INFO_LOG_LENGTH, &logLength);
+     if (logLength > 0)
+     {
+     GLchar *log = (GLchar *)malloc(logLength);
+     glGetProgramInfoLog(prog, logLength, &logLength, log);
+     NSLog(@"Program validate log:\n%s", log);
+     free(log);
+     }
+     
+     glGetProgramiv(prog, GL_VALIDATE_STATUS, &status);
+     if (status == 0)
+     return FALSE;
+     
+     return TRUE;
+     }
+     
+     */
+
 };
     
 } // namespace J