/*

     File: RootViewController.m

 Abstract: View controller to manage a scrollview that displays a zoomable image.

  Version: 1.3

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 */

#import "RootViewController.h"

#define ZOOM_VIEW_TAG 100

#define ZOOM_STEP 1.5

@interface RootViewController (UtilityMethods)

- (CGRect)zoomRectForScale:(float)scale withCenter:(CGPoint)center;

@end

@implementation RootViewController

@synthesize imageScrollView, imageView;

- (void)loadView {

    [super loadView];

    // set the tag for the image view

    [imageView setTag:ZOOM_VIEW_TAG];

    // add gesture recognizers to the image view

    UITapGestureRecognizer *singleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleSingleTap:)];

    UITapGestureRecognizer *doubleTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleDoubleTap:)];

    UITapGestureRecognizer *twoFingerTap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(handleTwoFingerTap:)];

    [doubleTap setNumberOfTapsRequired:2];

    [twoFingerTap setNumberOfTouchesRequired:2];

    [imageView addGestureRecognizer:singleTap];

    [imageView addGestureRecognizer:doubleTap];

    [imageView addGestureRecognizer:twoFingerTap];

    [singleTap release];

    [doubleTap release];

    [twoFingerTap release];

    // calculate minimum scale to perfectly fit image width, and begin at that scale

    float minimumScale = [imageScrollView frame].size.width  / [imageView frame].size.width;

    [imageScrollView setMinimumZoomScale:minimumScale];

    [imageScrollView setZoomScale:minimumScale];

}

- (void)viewDidUnload {

    self.imageScrollView = nil;

    self.imageView = nil;

}

- (void)dealloc {

    [imageScrollView release];

    [imageView release];

    [super dealloc];

}

#pragma mark UIScrollViewDelegate methods

- (UIView *)viewForZoomingInScrollView:(UIScrollView *)scrollView {

    return [imageScrollView viewWithTag:ZOOM_VIEW_TAG];

}

/************************************** NOTE **************************************/

/* The following delegate method works around a known bug in zoomToRect:animated: */

/* In the next release after 3.0 this workaround will no longer be necessary      */

/**********************************************************************************/

- (void)scrollViewDidEndZooming:(UIScrollView *)scrollView withView:(UIView *)view atScale:(float)scale {

    [scrollView setZoomScale:scale+0.01 animated:NO];

    [scrollView setZoomScale:scale animated:NO];

}

#pragma mark TapDetectingImageViewDelegate methods

- (void)handleSingleTap:(UIGestureRecognizer *)gestureRecognizer {

    // single tap does nothing for now

}

- (void)handleDoubleTap:(UIGestureRecognizer *)gestureRecognizer {

    // double tap zooms in

    float newScale = [imageScrollView zoomScale] * ZOOM_STEP;

    CGRect zoomRect = [self zoomRectForScale:newScale withCenter:[gestureRecognizer locationInView:gestureRecognizer.view]];

    [imageScrollView zoomToRect:zoomRect animated:YES];

}

- (void)handleTwoFingerTap:(UIGestureRecognizer *)gestureRecognizer {

    // two-finger tap zooms out

    float newScale = [imageScrollView zoomScale] / ZOOM_STEP;

    CGRect zoomRect = [self zoomRectForScale:newScale withCenter:[gestureRecognizer locationInView:gestureRecognizer.view]];

    [imageScrollView zoomToRect:zoomRect animated:YES];

}

#pragma mark Utility methods

- (CGRect)zoomRectForScale:(float)scale withCenter:(CGPoint)center {

    CGRect zoomRect;

    // the zoom rect is in the content view's coordinates. 

    //    At a zoom scale of 1.0, it would be the size of the imageScrollView's bounds.

    //    As the zoom scale decreases, so more content is visible, the size of the rect grows.

    zoomRect.size.height = [imageScrollView frame].size.height / scale;

    zoomRect.size.width  = [imageScrollView frame].size.width  / scale;

    // choose an origin so as to get the right center.

    zoomRect.origin.x    = center.x - (zoomRect.size.width  / 2.0);

    zoomRect.origin.y    = center.y - (zoomRect.size.height / 2.0);

    return zoomRect;

}

@end