/*

     File: TapDetectingView.m

 Abstract: UIView subclass that responds to taps and notifies its delegate.

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#import "TapDetectingView.h"

#define DOUBLE_TAP_DELAY 0.35

CGPoint midpointBetweenPoints(CGPoint a, CGPoint b);

@interface TapDetectingView ()

- (void)handleSingleTap;

- (void)handleDoubleTap;

- (void)handleTwoFingerTap;

@end

@implementation TapDetectingView

@synthesize delegate;

- (id)initWithFrame:(CGRect)frame {

    self = [super initWithFrame:frame];

    if (self) {

        [self setUserInteractionEnabled:YES];

        [self setMultipleTouchEnabled:YES];

        twoFingerTapIsPossible = YES;

        multipleTouches = NO;

    }

    return self;

}

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event

{

    // cancel any pending handleSingleTap messages 

    [NSObject cancelPreviousPerformRequestsWithTarget:self selector:@selector(handleSingleTap) object:nil];

    // update our touch state

    if ([[event touchesForView:self] count] > 1)

        multipleTouches = YES;

    if ([[event touchesForView:self] count] > 2)

        twoFingerTapIsPossible = NO;

}

- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event

{

    BOOL allTouchesEnded = ([touches count] == [[event touchesForView:self] count]);

    // first check for plain single/double tap, which is only possible if we haven't seen multiple touches

    if (!multipleTouches) {

        UITouch *touch = [touches anyObject];

        tapLocation = [touch locationInView:self];

        if ([touch tapCount] == 1) {

            [self performSelector:@selector(handleSingleTap) withObject:nil afterDelay:DOUBLE_TAP_DELAY];

        } else if([touch tapCount] == 2) {

            [self handleDoubleTap];

        }

    }    

    // check for 2-finger tap if we've seen multiple touches and haven't yet ruled out that possibility

    else if (multipleTouches && twoFingerTapIsPossible) { 

        // case 1: this is the end of both touches at once 

        if ([touches count] == 2 && allTouchesEnded) {

            int i = 0; 

            int tapCounts[2]; CGPoint tapLocations[2];

            for (UITouch *touch in touches) {

                tapCounts[i]    = [touch tapCount];

                tapLocations[i] = [touch locationInView:self];

                i++;

            }

            if (tapCounts[0] == 1 && tapCounts[1] == 1) { // it's a two-finger tap if they're both single taps

                tapLocation = midpointBetweenPoints(tapLocations[0], tapLocations[1]);

                [self handleTwoFingerTap];

            }

        }

        // case 2: this is the end of one touch, and the other hasn't ended yet

        else if ([touches count] == 1 && !allTouchesEnded) {

            UITouch *touch = [touches anyObject];

            if ([touch tapCount] == 1) {

                // if touch is a single tap, store its location so we can average it with the second touch location

                tapLocation = [touch locationInView:self];

            } else {

                twoFingerTapIsPossible = NO;

            }

        }

        // case 3: this is the end of the second of the two touches

        else if ([touches count] == 1 && allTouchesEnded) {

            UITouch *touch = [touches anyObject];

            if ([touch tapCount] == 1) {

                // if the last touch up is a single tap, this was a 2-finger tap

                tapLocation = midpointBetweenPoints(tapLocation, [touch locationInView:self]);

                [self handleTwoFingerTap];

            }

        }

    }

    // if all touches are up, reset touch monitoring state

    if (allTouchesEnded) {

        twoFingerTapIsPossible = YES;

        multipleTouches = NO;

    }

}

- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event {

    twoFingerTapIsPossible = YES;

    multipleTouches = NO;

}

#pragma mark Private

- (void)handleSingleTap {

    if ([delegate respondsToSelector:@selector(tapDetectingView:gotSingleTapAtPoint:)])

        [delegate tapDetectingView:self gotSingleTapAtPoint:tapLocation];

}

- (void)handleDoubleTap {

    if ([delegate respondsToSelector:@selector(tapDetectingView:gotDoubleTapAtPoint:)])

        [delegate tapDetectingView:self gotDoubleTapAtPoint:tapLocation];

}

- (void)handleTwoFingerTap {

    if ([delegate respondsToSelector:@selector(tapDetectingView:gotTwoFingerTapAtPoint:)])

        [delegate tapDetectingView:self gotTwoFingerTapAtPoint:tapLocation];

}

@end

CGPoint midpointBetweenPoints(CGPoint a, CGPoint b) {

    CGFloat x = (a.x + b.x) / 2.0;

    CGFloat y = (a.y + b.y) / 2.0;

    return CGPointMake(x, y);

}