BCCollectionViewLayoutOperation.m

//  Created by Pieter Omvlee on 02/03/2011.
//  Copyright 2011 Bohemian Coding. All rights reserved.

#import "BCCollectionViewLayoutOperation.h"
#import "BCCollectionView.h"
#import "BCCollectionViewLayoutItem.h"
#import "BCCollectionViewGroup.h"
#import "BCCollectionViewLayoutManager.h"

@implementation BCCollectionViewLayoutOperation
@synthesize layoutCallBack, collectionView, layoutCompletionBlock;

- (void)main
{
  if ([self isCancelled])
    return;
  
  NSInteger numberOfRows = 0;
  NSInteger y = 0;
  NSUInteger colIndex   = 0;
  NSRect visibleRect    = [collectionView visibleRect];
  NSSize cellSize       = [collectionView cellSize];
  NSSize inset          = NSZeroSize;
  NSInteger maxColumns  = [[collectionView layoutManager] maximumNumberOfItemsPerRow];
    NSUInteger gap        = (NSWidth([collectionView frame]) - maxColumns*cellSize.width)/(maxColumns+1);
    NSInteger startingX = gap;
    NSInteger x = gap;
  
  if ([[collectionView delegate] respondsToSelector:@selector(insetMarginForSelectingItemsInCollectionView:)])
    inset = [[collectionView delegate] insetMarginForSelectingItemsInCollectionView:collectionView];
  
  NSMutableArray *newLayouts   = [NSMutableArray array];
  NSEnumerator *groupEnum      = [[collectionView groups] objectEnumerator];
  BCCollectionViewGroup *group = [groupEnum nextObject];
  
  if (![group isCollapsed] && [[collectionView delegate] respondsToSelector:@selector(topOffsetForItemsInCollectionView:)])
    y += [[collectionView delegate] topOffsetForItemsInCollectionView:collectionView];
  
  NSUInteger count = [[collectionView contentArray] count];
  for (NSInteger i=0; i<count; i++) {
    if ([self isCancelled])
      return;
    
    if (group && [group itemRange].location == i) {
      if (x != startingX) {
        numberOfRows++;
        colIndex = 0;
        y += cellSize.height;
      }
      y += [collectionView groupHeaderHeight];
      x = startingX;
    }
    BCCollectionViewLayoutItem *item = [BCCollectionViewLayoutItem layoutItem];
    [item setItemIndex:i];
    if (![group isCollapsed]) {
      if (x + cellSize.width > NSMaxX(visibleRect)) {
        numberOfRows++;
        colIndex = 0;
        y += cellSize.height;
        x  = startingX;
      }
      [item setColumnIndex:colIndex];
      [item setItemRect:NSMakeRect(x, y, cellSize.width, cellSize.height)];
      x += cellSize.width + gap;
      colIndex++;
    } else {
      [item setItemRect:NSMakeRect(-cellSize.width*2, y, cellSize.width, cellSize.height)];
    }
    [item setItemContentRect:NSInsetRect([item itemRect], inset.width, inset.height)];
    [item setRowIndex:numberOfRows];
    [newLayouts addObject:item];
    
    if (layoutCallBack != nil) {
      dispatch_async(dispatch_get_main_queue(), ^{
        layoutCallBack(item);
      });
    }
    if ([group itemRange].location + [group itemRange].length-1 == i)
      group = [groupEnum nextObject];
  }
  numberOfRows = MAX(numberOfRows, [[collectionView groups] count]);
  if ([[collectionView contentArray] count] > 0 && numberOfRows == -1)
    numberOfRows = 1;
  
  if (![self isCancelled]) {
    dispatch_async(dispatch_get_main_queue(), ^{
      [[collectionView layoutManager] setItemLayouts:newLayouts];
      layoutCompletionBlock();
    });
  }
}

- (void)dealloc
{
  [layoutCallBack release];
  [layoutCompletionBlock release];
  [super dealloc];
}

@end