/*

     File: GLGravityView.m

 Abstract: This class wraps the CAEAGLLayer from CoreAnimation into a convenient

 UIView subclass. The view content is basically an EAGL surface you render your

 OpenGL scene into.  Note that setting the view non-opaque will only work if the

 EAGL surface has an alpha channel.

  Version: 2.2

 Disclaimer: IMPORTANT:  This Apple software is supplied to you by Apple

 Inc. ("Apple") in consideration of your agreement to the following

 terms, and your use, installation, modification or redistribution of

 this Apple software constitutes acceptance of these terms.  If you do

 not agree with these terms, please do not use, install, modify or

 redistribute this Apple software.

 In consideration of your agreement to abide by the following terms, and

 subject to these terms, Apple grants you a personal, non-exclusive

 license, under Apple's copyrights in this original Apple software (the

 "Apple Software"), to use, reproduce, modify and redistribute the Apple

 Software, with or without modifications, in source and/or binary forms;

 provided that if you redistribute the Apple Software in its entirety and

 without modifications, you must retain this notice and the following

 text and disclaimers in all such redistributions of the Apple Software.

 Neither the name, trademarks, service marks or logos of Apple Inc. may

 be used to endorse or promote products derived from the Apple Software

 without specific prior written permission from Apple.  Except as

 expressly stated in this notice, no other rights or licenses, express or

 implied, are granted by Apple herein, including but not limited to any

 patent rights that may be infringed by your derivative works or by other

 works in which the Apple Software may be incorporated.

 The Apple Software is provided by Apple on an "AS IS" basis.  APPLE

 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION

 THE IMPLIED WARRANTIES OF NON-INFRINGEMENT, MERCHANTABILITY AND FITNESS

 FOR A PARTICULAR PURPOSE, REGARDING THE APPLE SOFTWARE OR ITS USE AND

 OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.

 IN NO EVENT SHALL APPLE BE LIABLE FOR ANY SPECIAL, INDIRECT, INCIDENTAL

 OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

 INTERRUPTION) ARISING IN ANY WAY OUT OF THE USE, REPRODUCTION,

 MODIFICATION AND/OR DISTRIBUTION OF THE APPLE SOFTWARE, HOWEVER CAUSED

 AND WHETHER UNDER THEORY OF CONTRACT, TORT (INCLUDING NEGLIGENCE),

 STRICT LIABILITY OR OTHERWISE, EVEN IF APPLE HAS BEEN ADVISED OF THE

 POSSIBILITY OF SUCH DAMAGE.

 Copyright (C) 2010 Apple Inc. All Rights Reserved.

*/

#import <QuartzCore/QuartzCore.h>

#import <OpenGLES/EAGLDrawable.h>

#import "GLGravityView.h"

#import "teapot.h"

// CONSTANTS

#define kTeapotScale                3.0

// MACROS

#define DEGREES_TO_RADIANS(__ANGLE__) ((__ANGLE__) / 180.0 * M_PI)

// A class extension to declare private methods

@interface GLGravityView (private)

- (BOOL)createFramebuffer;

- (void)destroyFramebuffer;

- (void)setupView;

@end

@implementation GLGravityView

@synthesize animating;

@dynamic animationFrameInterval;

@synthesize accel;

// Implement this to override the default layer class (which is [CALayer class]).

// We do this so that our view will be backed by a layer that is capable of OpenGL ES rendering.

+ (Class) layerClass

{

    return [CAEAGLLayer class];

}

// The GL view is stored in the nib file. When it's unarchived it's sent -initWithCoder:

- (id)initWithCoder:(NSCoder*)coder {

    if ((self = [super initWithCoder:coder])) {

        CAEAGLLayer *eaglLayer = (CAEAGLLayer *)self.layer;

        eaglLayer.opaque = YES;

        eaglLayer.drawableProperties = [NSDictionary dictionaryWithObjectsAndKeys:

                                    [NSNumber numberWithBool:NO], kEAGLDrawablePropertyRetainedBacking, kEAGLColorFormatRGBA8, kEAGLDrawablePropertyColorFormat, nil];

        context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES1];

        if (!context || ![EAGLContext setCurrentContext:context]) {

            [self release];

            return nil;

        }

        animating = FALSE;

        displayLinkSupported = FALSE;

        animationFrameInterval = 1;

        displayLink = nil;

        animationTimer = nil;

        // A system version of 3.1 or greater is required to use CADisplayLink. The NSTimer

        // class is used as fallback when it isn't available.

        NSString *reqSysVer = @"3.1";

        NSString *currSysVer = [[UIDevice currentDevice] systemVersion];

        if ([currSysVer compare:reqSysVer options:NSNumericSearch] != NSOrderedAscending)

            displayLinkSupported = TRUE;

        accel = calloc(3, sizeof(UIAccelerationValue));

        [self setupView];

    }

    return self;

}

-(void)setupView

{

    const GLfloat           lightAmbient[] = {0.2, 0.2, 0.2, 1.0};

    const GLfloat           lightDiffuse[] = {1.0, 0.6, 0.0, 1.0};

    const GLfloat           matAmbient[] = {0.6, 0.6, 0.6, 1.0};

    const GLfloat           matDiffuse[] = {1.0, 1.0, 1.0, 1.0};    

    const GLfloat           matSpecular[] = {1.0, 1.0, 1.0, 1.0};

    const GLfloat           lightPosition[] = {0.0, 0.0, 1.0, 0.0}; 

    const GLfloat           lightShininess = 100.0,

                            zNear = 0.1,

                            zFar = 1000.0,

                            fieldOfView = 60.0;

    GLfloat                 size;

    //Configure OpenGL lighting

    glEnable(GL_LIGHTING);

    glEnable(GL_LIGHT0);

    glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, matAmbient);

    glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, matDiffuse);

    glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, matSpecular);

    glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, lightShininess);

    glLightfv(GL_LIGHT0, GL_AMBIENT, lightAmbient);

    glLightfv(GL_LIGHT0, GL_DIFFUSE, lightDiffuse);

    glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);           

    glShadeModel(GL_SMOOTH);

    glEnable(GL_DEPTH_TEST);

    //Configure OpenGL arrays

    glEnableClientState(GL_VERTEX_ARRAY);

    glEnableClientState(GL_NORMAL_ARRAY);

    glVertexPointer(3 ,GL_FLOAT, 0, teapot_vertices);

    glNormalPointer(GL_FLOAT, 0, teapot_normals);

    glEnable(GL_NORMALIZE);

    //Set the OpenGL projection matrix

    glMatrixMode(GL_PROJECTION);

    size = zNear * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0);

    CGRect rect = self.bounds;

    glFrustumf(-size, size, -size / (rect.size.width / rect.size.height), size / (rect.size.width / rect.size.height), zNear, zFar);

    glViewport(0, 0, rect.size.width, rect.size.height);

    //Make the OpenGL modelview matrix the default

    glMatrixMode(GL_MODELVIEW);

}

// Updates the OpenGL view

- (void)drawView

{

    // Make sure that you are drawing to the current context

    [EAGLContext setCurrentContext:context];

    glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);

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

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    GLfloat matrix[4][4], length;

    //Make sure we have a big enough acceleration vector

    length = sqrtf(accel[0] * accel[0] + accel[1] * accel[1] + accel[2] * accel[2]);

    //Setup model view matrix

    glLoadIdentity();

    glTranslatef(0.0, -0.1, -1.0);

    glScalef(kTeapotScale, kTeapotScale, kTeapotScale);

    if(length >= 0.1)

    {

        //Clear matrix to be used to rotate from the current referential to one based on the gravity vector

        bzero(matrix, sizeof(matrix));

        matrix[3][3] = 1.0;

        //Setup first matrix column as gravity vector

        matrix[0][0] = accel[0] / length;

        matrix[0][1] = accel[1] / length;

        matrix[0][2] = accel[2] / length;

        //Setup second matrix column as an arbitrary vector in the plane perpendicular to the gravity vector {Gx, Gy, Gz} defined by by the equation "Gx * x + Gy * y + Gz * z = 0" in which we arbitrarily set x=0 and y=1

        matrix[1][0] = 0.0;

        matrix[1][1] = 1.0;

        matrix[1][2] = -accel[1] / accel[2];

        length = sqrtf(matrix[1][0] * matrix[1][0] + matrix[1][1] * matrix[1][1] + matrix[1][2] * matrix[1][2]);

        matrix[1][0] /= length;

        matrix[1][1] /= length;

        matrix[1][2] /= length;

        //Setup third matrix column as the cross product of the first two

        matrix[2][0] = matrix[0][1] * matrix[1][2] - matrix[0][2] * matrix[1][1];

        matrix[2][1] = matrix[1][0] * matrix[0][2] - matrix[1][2] * matrix[0][0];

        matrix[2][2] = matrix[0][0] * matrix[1][1] - matrix[0][1] * matrix[1][0];

        //Finally load matrix

        glMultMatrixf((GLfloat*)matrix);

        // Rotate a bit more so that its where we want it.

        glRotatef(90.0, 0.0, 0.0, 1.0);

    }

    // If we're in the simulator we'd like to do something more interesting than just sit there

    // But if we're on a device, we want to just let the accelerometer do the work for us without a fallback.

#if TARGET_IPHONE_SIMULATOR

    else

    {

        static GLfloat spinX = 0.0, spinY = 0.0;

        glRotatef(spinX, 0.0, 0.0, 1.0);

        glRotatef(spinY, 0.0, 1.0, 0.0);

        glRotatef(90.0, 1.0, 0.0, 0.0);

        spinX += 1.0;

        spinY += 0.25;

    }

#endif

    // Draw teapot. The new_teapot_indicies array is an RLE (run-length encoded) version of the teapot_indices array in teapot.h

    for(int i = 0; i < num_teapot_indices; i += new_teapot_indicies[i] + 1)

    {

        glDrawElements(GL_TRIANGLE_STRIP, new_teapot_indicies[i], GL_UNSIGNED_SHORT, &new_teapot_indicies[i+1]);

    }

    glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);

    [context presentRenderbuffer:GL_RENDERBUFFER_OES];

}

// If our view is resized, we'll be asked to layout subviews.

// This is the perfect opportunity to also update the framebuffer so that it is

// the same size as our display area.

-(void)layoutSubviews

{

    [EAGLContext setCurrentContext:context];

    [self destroyFramebuffer];

    [self createFramebuffer];

    [self drawView];

}

- (BOOL)createFramebuffer

{

    // Generate IDs for a framebuffer object and a color renderbuffer

    glGenFramebuffersOES(1, &viewFramebuffer);

    glGenRenderbuffersOES(1, &viewRenderbuffer);

    glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer);

    glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer);

    // This call associates the storage for the current render buffer with the EAGLDrawable (our CAEAGLLayer)

    // allowing us to draw into a buffer that will later be rendered to screen wherever the layer is (which corresponds with our view).

    [context renderbufferStorage:GL_RENDERBUFFER_OES fromDrawable:(id<EAGLDrawable>)self.layer];

    glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_RENDERBUFFER_OES, viewRenderbuffer);

    glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_WIDTH_OES, &backingWidth);

    glGetRenderbufferParameterivOES(GL_RENDERBUFFER_OES, GL_RENDERBUFFER_HEIGHT_OES, &backingHeight);

    // For this sample, we also need a depth buffer, so we'll create and attach one via another renderbuffer.

    glGenRenderbuffersOES(1, &depthRenderbuffer);

    glBindRenderbufferOES(GL_RENDERBUFFER_OES, depthRenderbuffer);

    glRenderbufferStorageOES(GL_RENDERBUFFER_OES, GL_DEPTH_COMPONENT16_OES, backingWidth, backingHeight);

    glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_DEPTH_ATTACHMENT_OES, GL_RENDERBUFFER_OES, depthRenderbuffer);

    if(glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES) != GL_FRAMEBUFFER_COMPLETE_OES)

    {

        NSLog(@"failed to make complete framebuffer object %x", glCheckFramebufferStatusOES(GL_FRAMEBUFFER_OES));

        return NO;

    }

    return YES;

}

// Clean up any buffers we have allocated.

- (void)destroyFramebuffer

{

    glDeleteFramebuffersOES(1, &viewFramebuffer);

    viewFramebuffer = 0;

    glDeleteRenderbuffersOES(1, &viewRenderbuffer);

    viewRenderbuffer = 0;

    if(depthRenderbuffer)

    {

        glDeleteRenderbuffersOES(1, &depthRenderbuffer);

        depthRenderbuffer = 0;

    }

}

- (NSInteger) animationFrameInterval

{

    return animationFrameInterval;

}

- (void) setAnimationFrameInterval:(NSInteger)frameInterval

{

    // Frame interval defines how many display frames must pass between each time the

    // display link fires. The display link will only fire 30 times a second when the

    // frame internal is two on a display that refreshes 60 times a second. The default

    // frame interval setting of one will fire 60 times a second when the display refreshes

    // at 60 times a second. A frame interval setting of less than one results in undefined

    // behavior.

    if (frameInterval >= 1)

    {

        animationFrameInterval = frameInterval;

        if (animating)

        {

            [self stopAnimation];

            [self startAnimation];

        }

    }

}

- (void) startAnimation

{

    if (!animating)

    {

        if (displayLinkSupported)

        {

            // CADisplayLink is API new to iPhone SDK 3.1. Compiling against earlier versions will result in a warning, but can be dismissed

            // if the system version runtime check for CADisplayLink exists in -initWithCoder:. The runtime check ensures this code will

            // not be called in system versions earlier than 3.1.

            displayLink = [NSClassFromString(@"CADisplayLink") displayLinkWithTarget:self selector:@selector(drawView)];

            [displayLink setFrameInterval:animationFrameInterval];

            [displayLink addToRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];

        }

        else

            animationTimer = [NSTimer scheduledTimerWithTimeInterval:(NSTimeInterval)((1.0 / 60.0) * animationFrameInterval) target:self selector:@selector(drawView) userInfo:nil repeats:TRUE];

        animating = TRUE;

    }

}

- (void)stopAnimation

{

    if (animating)

    {

        if (displayLinkSupported)

        {

            [displayLink invalidate];

            displayLink = nil;

        }

        else

        {

            [animationTimer invalidate];

            animationTimer = nil;

        }

        animating = FALSE;

    }

}

- (void)dealloc

{

    free(accel);

    if([EAGLContext currentContext] == context)

    {

        [EAGLContext setCurrentContext:nil];

    }

    [context release];

    [super dealloc];

}

@end