/*

     File: APLDecorationView.m

 Abstract: n/a

  Version: 1.3

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#import "APLDecorationView.h"

@interface APLDecorationView ()

@property (nonatomic, strong) UIView *attachmentPointView;

@property (nonatomic, strong) UIView *attachedView;

@property (nonatomic, readwrite) CGPoint attachmentOffset;

//! Array of CALayer objects, each with the contents of an image

//! for a dash.

@property (nonatomic, strong) NSMutableArray *attachmentDecorationLayers;

@property (nonatomic, weak) IBOutlet UIImageView *centerPointView;

@property (nonatomic, weak) UIImageView *arrowView;

@end

@implementation APLDecorationView

//| ----------------------------------------------------------------------------

- (id)initWithCoder:(NSCoder *)aDecoder

{

    self = [super initWithCoder:aDecoder];

    if (self)

    {

        self.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"BackgroundTile"]];

    }

    return self;

}

//| ----------------------------------------------------------------------------

- (void)dealloc

{

    [self.attachmentPointView removeObserver:self forKeyPath:@"center"];

    [self.attachedView removeObserver:self forKeyPath:@"center"];

}

//| ----------------------------------------------------------------------------

//! Draws an arrow with a given @a length anchored at the center of the receiver,

//! that points in the direction given by @a angle.

//

- (void)drawMagnitudeVectorWithLength:(CGFloat)length angle:(CGFloat)angle color:(UIColor*)arrowColor forLimitedTime:(BOOL)temporary

{

    if (!self.arrowView)

    // First time initialization.

    {

        UIImage *arrowImage = [[UIImage imageNamed:@"Arrow"] imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];

        UIImageView *arrowImageView = [[UIImageView alloc] initWithImage:arrowImage];

        arrowImageView.bounds = CGRectMake(0, 0, arrowImage.size.width, arrowImage.size.height);

        arrowImageView.contentMode = UIViewContentModeRight;

        arrowImageView.clipsToBounds = YES;

        arrowImageView.layer.anchorPoint = CGPointMake(0.0, 0.5);

        [self addSubview:arrowImageView];

        [self sendSubviewToBack:arrowImageView];

        self.arrowView = arrowImageView;

    }

    self.arrowView.bounds = CGRectMake(0, 0, length, self.arrowView.bounds.size.height);

    self.arrowView.transform = CGAffineTransformMakeRotation(angle);

    self.arrowView.tintColor = arrowColor;

    self.arrowView.alpha = 1;

    if (temporary)

        [UIView animateWithDuration:1.0 animations:^{

            self.arrowView.alpha = 0;

        }];

}

//| ----------------------------------------------------------------------------

//! Draws a dashed line between @a attachmentPointView and @a attachedView

//! that is updated as either view moves.

//

- (void)trackAndDrawAttachmentFromView:(UIView*)attachmentPointView toView:(UIView*)attachedView withAttachmentOffset:(CGPoint)attachmentOffset

{

    if (!self.attachmentDecorationLayers)

    // First time initialization.

    {

        self.attachmentDecorationLayers = [NSMutableArray arrayWithCapacity:4];

        for (NSUInteger i=0; i<4; i++)

        {

            UIImage *dashImage = [UIImage imageNamed:[NSString stringWithFormat:@"DashStyle%i", (i % 3) + 1]];

            CALayer *dashLayer = [CALayer layer];

            dashLayer.contents = (__bridge id)(dashImage.CGImage);

            dashLayer.bounds = CGRectMake(0, 0, dashImage.size.width, dashImage.size.height);

            dashLayer.anchorPoint = CGPointMake(0.5, 0);

            [self.layer insertSublayer:dashLayer atIndex:0];

            [self.attachmentDecorationLayers addObject:dashLayer];

        }

    }

    // A word about performance.

    // Tracking changes to the properties of any id<UIDynamicItem> involved in

    // a simulation incurs a performance cost.  You will receive a callback

    // during each step in the simulation in which the tracked item is not at

    // rest.  You should therefore strive to make your callback code as

    // efficient as possible.

    [self.attachmentPointView removeObserver:self forKeyPath:@"center"];

    [self.attachedView removeObserver:self forKeyPath:@"center"];

    self.attachmentPointView = attachmentPointView;

    self.attachedView = attachedView;

    self.attachmentOffset = attachmentOffset;

    // Observe the 'center' property of both views to know when they move.

    [self.attachmentPointView addObserver:self forKeyPath:@"center" options:0 context:NULL];

    [self.attachedView addObserver:self forKeyPath:@"center" options:0 context:NULL];

    [self setNeedsLayout];

}

//| ----------------------------------------------------------------------------

- (void)layoutSubviews

{

    [super layoutSubviews];

    self.arrowView.center = CGPointMake(CGRectGetMidX(self.bounds), CGRectGetMidY(self.bounds));

    if (self.centerPointView)

        self.centerPointView.center = CGPointMake(CGRectGetMidX(self.bounds), CGRectGetMidY(self.bounds));

    if (self.attachmentDecorationLayers)

    {

        // Here we adjust the line dash pattern visualizing the attachement

        // between attachmentPointView and attachedView to account for a change

        // in the position of either.

        const NSUInteger MaxDashes = self.attachmentDecorationLayers.count;

        CGPoint attachmentPointViewCenter = CGPointMake(self.attachmentPointView.bounds.size.width/2, self.attachmentPointView.bounds.size.height/2);

        attachmentPointViewCenter = [self.attachmentPointView convertPoint:attachmentPointViewCenter toView:self];

        CGPoint attachedViewAttachmentPoint = CGPointMake(self.attachedView.bounds.size.width/2 + self.attachmentOffset.x, self.attachedView.bounds.size.height/2 + self.attachmentOffset.y);

        attachedViewAttachmentPoint =  [self.attachedView convertPoint:attachedViewAttachmentPoint toView:self];

        CGFloat distance = sqrtf( powf(attachedViewAttachmentPoint.x-attachmentPointViewCenter.x, 2.0) +

                                 powf(attachedViewAttachmentPoint.y-attachmentPointViewCenter.y, 2.0) );

        CGFloat angle = atan2( attachedViewAttachmentPoint.y-attachmentPointViewCenter.y,

                              attachedViewAttachmentPoint.x-attachmentPointViewCenter.x );

        NSUInteger requiredDashes = 0;

        CGFloat d = 0.0f;

        // Depending on the distance between the two views, a smaller number of

        // dashes may be needed to adequately visualize the attachment.  Starting

        // with a distance of 0, we add the length of each dash until we exceed

        // 'distance' computed previously or we use the maximum number of allowed

        // dashes, 'MaxDashes'.

        while (requiredDashes < MaxDashes)

        {

            CALayer *dashLayer = self.attachmentDecorationLayers[requiredDashes];

            if (d + dashLayer.bounds.size.height < distance) {

                d += dashLayer.bounds.size.height;

                dashLayer.hidden = NO;

                requiredDashes++;

            } else

                break;

        }

        // Based on the total length of the dashes we previously determined were

        // necessary to visualize the attachment, determine the spacing between

        // each dash.

        CGFloat dashSpacing = (distance - d) / (requiredDashes + 1);

        // Hide the excess dashes.

        for (; requiredDashes < MaxDashes; requiredDashes++)

            [self.attachmentDecorationLayers[requiredDashes] setHidden:YES];

        // Disable any animations.  The changes must take full effect immediately.

        [CATransaction begin];

        [CATransaction setAnimationDuration:0];

        // Each dash layer is positioned by altering its affineTransform.  We

        // combine the position of rotation into an affine transformation matrix

        // that is assigned to each dash.

        CGAffineTransform transform = CGAffineTransformMakeTranslation(attachmentPointViewCenter.x, attachmentPointViewCenter.y);

        transform = CGAffineTransformRotate(transform, angle - M_PI/2);

        for (NSUInteger drawnDashes = 0; drawnDashes < requiredDashes; drawnDashes++)

        {

            CALayer *dashLayer = self.attachmentDecorationLayers[drawnDashes];

            transform = CGAffineTransformTranslate(transform, 0, dashSpacing);

            [dashLayer setAffineTransform:transform];

            transform = CGAffineTransformTranslate(transform, 0, dashLayer.bounds.size.height);

        }

        [CATransaction commit];

    }

}

//| ----------------------------------------------------------------------------

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context

{

    if (object == self.attachmentPointView || object == self.attachedView)

        [self setNeedsLayout];

    else

        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];

}

@end