/*

     File: TiledScrollView.m

 Abstract: UIScrollView subclass to manage tiled content.

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#import <QuartzCore/QuartzCore.h>

#import "TiledScrollView.h"

#import "TapDetectingView.h"

#define DEFAULT_TILE_SIZE 100

#define ANNOTATE_TILES YES

@interface TiledScrollView ()

- (void)annotateTile:(UIView *)tile;

- (void)updateResolution;

@end

@implementation TiledScrollView

@synthesize tileSize;

@synthesize tileContainerView;

@synthesize dataSource;

@dynamic minimumResolution;

@dynamic maximumResolution;

- (id)initWithFrame:(CGRect)frame {

    if (self = [super initWithFrame:frame]) {

        // we will recycle tiles by removing them from the view and storing them here

        reusableTiles = [[NSMutableSet alloc] init];

        // we need a tile container view to hold all the tiles. This is the view that is returned

        // in the -viewForZoomingInScrollView: delegate method, and it also detects taps.

        tileContainerView = [[TapDetectingView alloc] initWithFrame:CGRectZero];

        [tileContainerView setBackgroundColor:[UIColor redColor]];

        [self addSubview:tileContainerView];

        [self setTileSize:CGSizeMake(DEFAULT_TILE_SIZE, DEFAULT_TILE_SIZE)];

        // no rows or columns are visible at first; note this by making the firsts very high and the lasts very low

        firstVisibleRow = firstVisibleColumn = NSIntegerMax;

        lastVisibleRow  = lastVisibleColumn  = NSIntegerMin;

        // the TiledScrollView is its own UIScrollViewDelegate, so we can handle our own zooming.

        // We need to return our tileContainerView as the view for zooming, and we also need to receive

        // the scrollViewDidEndZooming: delegate callback so we can update our resolution.

        [super setDelegate:self];

    }

    return self;

}

- (void)dealloc {

    [reusableTiles release];

    [tileContainerView release];

    [super dealloc];

}

// we don't synthesize our minimum/maximum resolution accessor methods because we want to police the values of these ivars

- (int)minimumResolution { return minimumResolution; }

- (int)maximumResolution { return maximumResolution; }

- (void)setMinimumResolution:(int)res { minimumResolution = MIN(res, 0); } // you can't have a minimum resolution greater than 0

- (void)setMaximumResolution:(int)res { maximumResolution = MAX(res, 0); } // you can't have a maximum resolution less than 0

- (UIView *)dequeueReusableTile {

    UIView *tile = [reusableTiles anyObject];

    if (tile) {

        // the only object retaining the tile is our reusableTiles set, so we have to retain/autorelease it

        // before returning it so that it's not immediately deallocated when we remove it from the set

        [[tile retain] autorelease];

        [reusableTiles removeObject:tile];

    }

    return tile;

}

- (void)reloadData {

    // recycle all tiles so that every tile will be replaced in the next layoutSubviews

    for (UIView *view in [tileContainerView subviews]) {

        [reusableTiles addObject:view];

        [view removeFromSuperview];

    }

    // no rows or columns are now visible; note this by making the firsts very high and the lasts very low

    firstVisibleRow = firstVisibleColumn = NSIntegerMax;

    lastVisibleRow  = lastVisibleColumn  = NSIntegerMin;

    [self setNeedsLayout];

}

- (void)reloadDataWithNewContentSize:(CGSize)size {

    // since we may have changed resolutions, which changes our maximum and minimum zoom scales, we need to 

    // reset all those values. After calling this method, the caller should change the maximum/minimum zoom scales

    // if it wishes to permit zooming.

    [self setZoomScale:1.0];

    [self setMinimumZoomScale:1.0];

    [self setMaximumZoomScale:1.0];

    resolution = 0;

    // now that we've reset our zoom scale and resolution, we can safely set our contentSize. 

    [self setContentSize:size];

    // we also need to change the frame of the tileContainerView so its size matches the contentSize

    [tileContainerView setFrame:CGRectMake(0, 0, size.width, size.height)];

    [self reloadData];

}

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

/* Most of the work of tiling is done in layoutSubviews, which we override here.   */

/* We recycle the tiles that are no longer in the visible bounds of the scrollView */

/* and we add any tiles that should now be present but are missing.                */

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

- (void)layoutSubviews {

    [super layoutSubviews];

    CGRect visibleBounds = [self bounds];

    // first recycle all tiles that are no longer visible

    for (UIView *tile in [tileContainerView subviews]) {

        // We want to see if the tiles intersect our (i.e. the scrollView's) bounds, so we need to convert their

        // frames to our own coordinate system

        CGRect scaledTileFrame = [tileContainerView convertRect:[tile frame] toView:self];

        // If the tile doesn't intersect, it's not visible, so we can recycle it

        if (! CGRectIntersectsRect(scaledTileFrame, visibleBounds)) {

            [reusableTiles addObject:tile];

            [tile removeFromSuperview];

        }

    }

    // calculate which rows and columns are visible by doing a bunch of math.

    float scaledTileWidth  = [self tileSize].width  * [self zoomScale];

    float scaledTileHeight = [self tileSize].height * [self zoomScale];

    int maxRow = floorf([tileContainerView frame].size.height / scaledTileHeight); // this is the maximum possible row

    int maxCol = floorf([tileContainerView frame].size.width  / scaledTileWidth);  // and the maximum possible column

    int firstNeededRow = MAX(0, floorf(visibleBounds.origin.y / scaledTileHeight));

    int firstNeededCol = MAX(0, floorf(visibleBounds.origin.x / scaledTileWidth));

    int lastNeededRow  = MIN(maxRow, floorf(CGRectGetMaxY(visibleBounds) / scaledTileHeight));

    int lastNeededCol  = MIN(maxCol, floorf(CGRectGetMaxX(visibleBounds) / scaledTileWidth));

    // iterate through needed rows and columns, adding any tiles that are missing

    for (int row = firstNeededRow; row <= lastNeededRow; row++) {

        for (int col = firstNeededCol; col <= lastNeededCol; col++) {

            BOOL tileIsMissing = (firstVisibleRow > row || firstVisibleColumn > col || 

                                  lastVisibleRow  < row || lastVisibleColumn  < col);

            if (tileIsMissing) {

                UIView *tile = [dataSource tiledScrollView:self tileForRow:row column:col resolution:resolution];

                // set the tile's frame so we insert it at the correct position

                CGRect frame = CGRectMake([self tileSize].width * col, [self tileSize].height * row, [self tileSize].width, [self tileSize].height);

                [tile setFrame:frame];

                [tileContainerView addSubview:tile];

                // annotateTile draws green lines and tile numbers on the tiles for illustration purposes. 

                [self annotateTile:tile];

            }

        }

    }

    // update our record of which rows/cols are visible

    firstVisibleRow = firstNeededRow; firstVisibleColumn = firstNeededCol;

    lastVisibleRow  = lastNeededRow;  lastVisibleColumn  = lastNeededCol;            

}

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

/* The following method handles changing the resolution of our tiles when our zoomScale  */

/* gets below 50% or above 100%. When we fall below 50%, we lower the resolution 1 step, */

/* and when we get above 100% we raise it 1 step. The resolution is stored as a power of */

/* 2, so -1 represents 50%, and 0 represents 100%, and so on.                            */

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

- (void)updateResolution {

    // delta will store the number of steps we should change our resolution by. If we've fallen below

    // a 25% zoom scale, for example, we should lower our resolution by 2 steps so delta will equal -2.

    // (Provided that lowering our resolution 2 steps stays within the limit imposed by minimumResolution.)

    int delta = 0;

    // check if we should decrease our resolution

    for (int thisResolution = minimumResolution; thisResolution < resolution; thisResolution++) {

        int thisDelta = thisResolution - resolution;

        // we decrease resolution by 1 step if the zoom scale is <= 0.5 (= 2^-1); by 2 steps if <= 0.25 (= 2^-2), and so on

        float scaleCutoff = pow(2, thisDelta); 

        if ([self zoomScale] <= scaleCutoff) {

            delta = thisDelta;

            break;

        } 

    }

    // if we didn't decide to decrease the resolution, see if we should increase it

    if (delta == 0) {

        for (int thisResolution = maximumResolution; thisResolution > resolution; thisResolution--) {

            int thisDelta = thisResolution - resolution;

            // we increase by 1 step if the zoom scale is > 1 (= 2^0); by 2 steps if > 2 (= 2^1), and so on

            float scaleCutoff = pow(2, thisDelta - 1); 

            if ([self zoomScale] > scaleCutoff) {

                delta = thisDelta;

                break;

            } 

        }

    }

    if (delta != 0) {

        resolution += delta;

        // if we're increasing resolution by 1 step we'll multiply our zoomScale by 0.5; up 2 steps multiply by 0.25, etc

        // if we're decreasing resolution by 1 step we'll multiply our zoomScale by 2.0; down 2 steps by 4.0, etc

        float zoomFactor = pow(2, delta * -1); 

        // save content offset, content size, and tileContainer size so we can restore them when we're done

        // (contentSize is not equal to containerSize when the container is smaller than the frame of the scrollView.)

        CGPoint contentOffset = [self contentOffset];   

        CGSize  contentSize   = [self contentSize];

        CGSize  containerSize = [tileContainerView frame].size;

        // adjust all zoom values (they double as we cut resolution in half)

        [self setMaximumZoomScale:[self maximumZoomScale] * zoomFactor];

        [self setMinimumZoomScale:[self minimumZoomScale] * zoomFactor];

        [super setZoomScale:[self zoomScale] * zoomFactor];

        // restore content offset, content size, and container size

        [self setContentOffset:contentOffset];

        [self setContentSize:contentSize];

        [tileContainerView setFrame:CGRectMake(0, 0, containerSize.width, containerSize.height)];    

        // throw out all tiles so they'll reload at the new resolution

        [self reloadData];        

    }        

}

#pragma mark UIScrollViewDelegate

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

    return tileContainerView;

}

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

    if (scrollView == self) {

        // the following two lines are a bug workaround that will no longer be needed after OS 3.0.

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

        [super setZoomScale:scale animated:NO];

        // after a zoom, check to see if we should change the resolution of our tiles

        [self updateResolution];

    }

}

#pragma mark UIScrollView overrides

// the scrollViewDidEndZooming: delegate method is only called after an *animated* zoom. We also need to update our 

// resolution for non-animated zooms. So we also override the new setZoomScale:animated: method on UIScrollView

- (void)setZoomScale:(float)scale animated:(BOOL)animated {

    [super setZoomScale:scale animated:animated];

    // the delegate callback will catch the animated case, so just cover the non-animated case

    if (!animated) {

        [self updateResolution];

    }

}

// We override the setDelegate: method because we can't manage resolution changes unless we are our own delegate.

- (void)setDelegate:(id)delegate {

    NSLog(@"You can't set the delegate of a TiledZoomableScrollView. It is its own delegate.");

}

#pragma mark

#define LABEL_TAG 3

- (void)annotateTile:(UIView *)tile {

    static int totalTiles = 0;

    UILabel *label = (UILabel *)[tile viewWithTag:LABEL_TAG];

    if (!label) {  

        totalTiles++;  // if we haven't already added a label to this tile, it's a new tile

        UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(5, 0, 80, 50)];

        [label setBackgroundColor:[UIColor clearColor]];

        [label setTag:LABEL_TAG];

        [label setTextColor:[UIColor greenColor]];

        [label setShadowColor:[UIColor blackColor]];

        [label setShadowOffset:CGSizeMake(1.0, 1.0)];

        [label setFont:[UIFont boldSystemFontOfSize:40]];

        [label setText:[NSString stringWithFormat:@"%d", totalTiles]];

        [tile addSubview:label];

        [label release];

        [[tile layer] setBorderWidth:2];

        [[tile layer] setBorderColor:[[UIColor greenColor] CGColor]];

    }

    [tile bringSubviewToFront:label];

}

@end