OpenGL failed texture binding - cocoa

Question

I am attempting to get my first shadow map up and running (from here), but I have run into a very strange problem. This is the code that causes the error:
#interface HSOpenGLView() {
GLuint shadowFramebuffer;
GLuint shadowTexture;
}
#end
#implementation HSOpenGLView
- (void) drawRect:(NSRect)dirtyRect {
}
#pragma mark - Init
- (void) prepareOpenGL {
[super prepareOpenGL];
glEnable(GL_TEXTURE_2D);
glGenFramebuffers(1, &shadowFramebuffer);
glBindFramebuffer(GL_FRAMEBUFFER, shadowFramebuffer);
// Depth texture. Slower than a depth buffer, but you can sample it later in your shader
glGenTextures(1, &shadowTexture);
glBindTexture(GL_TEXTURE_2D, shadowTexture);
glTexImage2D(GL_TEXTURE_2D, 0, GL_DEPTH_COMPONENT16, 1024, 1024, 0, GL_DEPTH_COMPONENT, GL_FLOAT, 0);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
//glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, shadowTexture, 0);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_TEXTURE_2D, shadowTexture, 0);
//glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, shadowTexture);
glDrawBuffer(GL_NONE); // No color buffer is drawn to.
// Always check that our framebuffer is ok
if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
NSLog(#"Failed to create the shadow framebuffer! %u", glGetError());
}
}
This class is a subclass of 'NSOpenGLView'. When it prints the error number it turns out to be '0'. What could possibly be causing it?

Answer 1

Add a call to glReadBuffer(GL_NONE) after your call to glDrawBuffer(GL_NONE). You need to indicate that your FBO doesn't have a color buffer source for read operations too.