//  MyGLLayer.h

//  CADemo

//

//  Created by Zenny Chen on 14-8-19.

//  Copyright (c) 2014年 Adwo. All rights reserved.

//

@import QuartzCore;

#import <OpenGLES/ES3/gl.h>

@interface MyGLLayer : CAEAGLLayer

{

@private

    /* The pixel dimensions of the backbuffer */

    GLint mBackingWidth;

    GLint mBackingHeight;

    EAGLContext *mContext;

    /* OpenGL names for the renderbuffer and framebuffers used to render to this view */

    GLuint mFramebuffer, mRenderbuffer, mDepthRenderbuffer;

    GLuint mMSAAFramebuffer, mMSAARenderbuffer, mMSAADepthRenderbuffer;

    CADisplayLink *mDisplayLink;

}

- (instancetype)init

{

    self = [super init];

    self.opaque = YES;

    self.contentsScale = [UIScreen mainScreen].scale;

    // Optionally configure the surface properties of the rendering surface by assigning a new dictionary of

    // values to the drawableProperties property of the CAEAGLLayer object.

    self.drawableProperties = @{

                                kEAGLDrawablePropertyRetainedBacking : @NO,

                                kEAGLDrawablePropertyColorFormat : kEAGLColorFormatRGBA8

                                };

    // Set OpenGL ES context，use GL ES3 profile

    mContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES3];

    return self;

}

- (BOOL)createFramebuffer

{

    // Create the framebuffer and bind it so that future OpenGL ES framebuffer commands are directed to it.

    glGenFramebuffers(, &mFramebuffer);

    glBindFramebuffer(GL_FRAMEBUFFER, mFramebuffer);

    // Create a color renderbuffer, allocate storage for it, and attach it to the framebuffer.

    glGenRenderbuffers(, &mRenderbuffer);

    glBindRenderbuffer(GL_RENDERBUFFER, mRenderbuffer);

    // Create the color renderbuffer and call the rendering context to allocate the storage on our Core Animation layer.

    // The width, height, and format of the renderbuffer storage are derived from the bounds and properties of the CAEAGLLayer object

    // at the moment the renderbufferStorage:fromDrawable: method is called.

    [mContext renderbufferStorage:GL_RENDERBUFFER fromDrawable:self];

    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, mRenderbuffer);

    // Retrieve the height and width of the color renderbuffer.

    glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_WIDTH, &mBackingWidth);

    glGetRenderbufferParameteriv(GL_RENDERBUFFER, GL_RENDERBUFFER_HEIGHT, &mBackingHeight);

    // Perform similar steps to create and attach a depth renderbuffer.

    glGenRenderbuffers(, &mDepthRenderbuffer);

    glBindRenderbuffer(GL_RENDERBUFFER, mDepthRenderbuffer);

    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, mBackingWidth, mBackingHeight);

    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, mDepthRenderbuffer);

    // The following is MSAA settings

    glGenFramebuffers(, &mMSAAFramebuffer);

    glBindFramebuffer(GL_FRAMEBUFFER, mMSAAFramebuffer);

    glGenRenderbuffers(, &mMSAARenderbuffer);

    glBindRenderbuffer(GL_RENDERBUFFER, mMSAARenderbuffer);

    // 4 samples for color

    glRenderbufferStorageMultisample(GL_RENDERBUFFER, , GL_RGBA8, mBackingWidth, mBackingHeight);

    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, mMSAARenderbuffer);

    glGenRenderbuffers(, &mMSAADepthRenderbuffer);

    glBindRenderbuffer(GL_RENDERBUFFER, mMSAADepthRenderbuffer);

    // 4 samples for depth

    glRenderbufferStorageMultisample(GL_RENDERBUFFER, , GL_DEPTH_COMPONENT16, mBackingWidth, mBackingHeight);

    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, mMSAADepthRenderbuffer);

    // Test the framebuffer for completeness.

    if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)

    {

        NSLog(@"failed to make complete framebuffer object %x", glCheckFramebufferStatus(GL_FRAMEBUFFER));

        return NO;

    }

    glViewport(, , mBackingWidth, mBackingHeight);

    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

   // Do other settings...

    return YES;

}

- (void)drawLayer:(CADisplayLink*)link

{

    glBindFramebuffer(GL_FRAMEBUFFER, mMSAAFramebuffer);

    glBindRenderbuffer(GL_RENDERBUFFER, mMSAARenderbuffer);

    // Draw something here...

    [self drawModels];

    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, mFramebuffer);

    glBindFramebuffer(GL_READ_FRAMEBUFFER, mMSAAFramebuffer);

#if 0

    // OpenGL ES 2.0 Apple multisampling

    // Discard the depth buffer from the read fbo. It is no more necessary.

    glDiscardFramebufferEXT(GL_READ_FRAMEBUFFER, , (GLenum[]){GL_DEPTH_ATTACHMENT});

    glResolveMultisampleFramebufferAPPLE();

    glDiscardFramebufferEXT(GL_READ_FRAMEBUFFER, , (GLenum[]){GL_COLOR_ATTACHMENT0});

#else

    // OpenGL ES3.0 Core multisampling

    // Discard the depth buffer from the read fbo. It is no more necessary.

    glInvalidateFramebuffer(GL_READ_FRAMEBUFFER, , (GLenum[]){GL_DEPTH_ATTACHMENT});

    // Copy the read fbo(multisampled framebuffer) to the draw fbo(single-sampled framebuffer)

    glBlitFramebuffer(, , mBackingWidth, mBackingHeight, , , mBackingWidth, mBackingHeight, GL_COLOR_BUFFER_BIT, GL_NEAREST);

    glInvalidateFramebuffer(GL_READ_FRAMEBUFFER, , (GLenum[]){GL_COLOR_ATTACHMENT0});

#endif

    glBindRenderbuffer(GL_RENDERBUFFER, mRenderbuffer);

    // Assuming you allocated a color renderbuffer to point at a Core Animation layer, you present its contents by making it the current renderbuffer

    // and calling the presentRenderbuffer: method on your rendering context.

    [mContext presentRenderbuffer:GL_RENDERBUFFER];

}