/*

     File: APLCrossDissolveRenderer.m

 Abstract:  APLCrossDissolveRenderer subclass of APLOpenGLRenderer, renders the given source buffers to perform a cross dissolve over the time range of the transition. 

  Version: 1.1

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#import "APLCrossDissolveRenderer.h"

@implementation APLCrossDissolveRenderer

- (id)init

{

    self = [super init];

    return self;

}

- (void)renderPixelBuffer:(CVPixelBufferRef)destinationPixelBuffer usingForegroundSourceBuffer:(CVPixelBufferRef)foregroundPixelBuffer andBackgroundSourceBuffer:(CVPixelBufferRef)backgroundPixelBuffer forTweenFactor:(float)tween

{

    CGLSetCurrentContext(_currentContext);

    CGLLockContext(_currentContext);

    if (foregroundPixelBuffer != NULL || backgroundPixelBuffer != NULL) {

        CVOpenGLTextureRef foregroundTexture  = [self textureForPixelBuffer:foregroundPixelBuffer];

        CVOpenGLTextureRef backgroundTexture = [self textureForPixelBuffer:backgroundPixelBuffer];

        CVOpenGLTextureRef destTexture = [self textureForPixelBuffer:destinationPixelBuffer];

        glUseProgram(self.program);

        // Set the render transform

        GLfloat preferredRenderTransform [] = {

            self.renderTransform.a, self.renderTransform.b, self.renderTransform.tx, 0.0,

            self.renderTransform.c, self.renderTransform.d, self.renderTransform.ty, 0.0,

            0.0,                       0.0,                                     1.0, 0.0,

            0.0,                       0.0,                                     0.0, 1.0,

        };

        glUniformMatrix4fv(uniforms[UNIFORM_RENDER_TRANSFORM], 1, GL_FALSE, preferredRenderTransform);

        glBindFramebuffer(GL_FRAMEBUFFER, self.offscreenBufferHandle);

        glViewport(0, 0, (int)CVPixelBufferGetWidth(destinationPixelBuffer), (int)CVPixelBufferGetHeight(destinationPixelBuffer));

        // Y planes of foreground and background frame are used to render the Y plane of the destination frame

        glActiveTexture(GL_TEXTURE0);

        glBindTexture(CVOpenGLTextureGetTarget(foregroundTexture), CVOpenGLTextureGetName(foregroundTexture));

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);

        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

        glActiveTexture(GL_TEXTURE1);

        glBindTexture(CVOpenGLTextureGetTarget(backgroundTexture), CVOpenGLTextureGetName(backgroundTexture));

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);

        glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

        glActiveTexture(GL_TEXTURE2);

        glBindTexture(CVOpenGLTextureGetTarget(destTexture), CVOpenGLTextureGetName(destTexture));

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); // GL_NEAREST

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); // 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);

        // Attach the destination texture as a color attachment to the off screen frame buffer

        glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, CVOpenGLTextureGetTarget(destTexture), CVOpenGLTextureGetName(destTexture), 0);

        if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {

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

            goto bail;

        }

        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);

        glClear(GL_COLOR_BUFFER_BIT);

        GLfloat quadVertexData1 [] = {

            -1.0, -1.0,

            1.0, -1.0,

            -1.0, 1.0,

            1.0, 1.0,

        };

        size_t frameWidth = CVPixelBufferGetWidth(destinationPixelBuffer);

        size_t frameHeight = CVPixelBufferGetHeight(destinationPixelBuffer);

        // texture data varies from 0 -> w and 0 -> h, whereas vertex data varies from -1 -> 1

        GLfloat quadTextureData1 [] = {

            (0.5 + quadVertexData1[0]/2) * frameWidth, (0.5 + quadVertexData1[1]/2) * frameHeight,

            (0.5 + quadVertexData1[2]/2) * frameWidth, (0.5 + quadVertexData1[3]/2) * frameHeight,

            (0.5 + quadVertexData1[4]/2) * frameWidth, (0.5 + quadVertexData1[5]/2) * frameHeight,

            (0.5 + quadVertexData1[6]/2) * frameWidth, (0.5 + quadVertexData1[7]/2) * frameHeight,

        };

        glUniform1i(uniforms[UNIFORM_RGB], 0);

        glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, 0, 0, quadVertexData1);

        glEnableVertexAttribArray(ATTRIB_VERTEX);

        glVertexAttribPointer(ATTRIB_TEXCOORD, 2, GL_FLOAT, 0, 0, quadTextureData1);

        glEnableVertexAttribArray(ATTRIB_TEXCOORD);

        // Blend function to draw the foreground frame

        glEnable(GL_BLEND);

        glBlendFunc(GL_ONE, GL_ZERO);

        // Draw the foreground frame

        glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

        glUniform1i(uniforms[UNIFORM_RGB], 1);

        glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, 0, 0, quadVertexData1);

        glEnableVertexAttribArray(ATTRIB_VERTEX);

        glVertexAttribPointer(ATTRIB_TEXCOORD, 2, GL_FLOAT, 0, 0, quadTextureData1);

        glEnableVertexAttribArray(ATTRIB_TEXCOORD);

        // Blend function to draw the background frame

        glBlendColor(0, 0, 0, tween);

        glBlendFunc(GL_CONSTANT_ALPHA, GL_ONE_MINUS_CONSTANT_ALPHA);

        // Draw the background frame

        glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);

        glFlush();

    bail:

        CFRelease(foregroundTexture);

        CFRelease(backgroundTexture);

        CFRelease(destTexture);

        // Periodic texture cache flush every frame

        CVOpenGLTextureCacheFlush(self.videoTextureCache, 0);

        CGLUnlockContext(_currentContext);

        CGLSetCurrentContext(_previousContext);

    }

}

@end