波紋（その３）

CoocaSliedsのコードを読む。いくつかクラスがあるが、トランジション処理は SlideshowViewクラス に記述されている。
SlideshowViewはNSViewのサブクラスでメンバ変数には、表示中のイメージやトランジションのスタイル、マスク画像などが保持されている。

@interface SlideshowView : NSView
{
    NSImageView     *currentImageView;          // an NSImageView that displays the current image, as a subview of the SlideshowView
    int             transitionStyle;            // the style of transition to use; one of the SlideshowViewTransitionStyle values enumerated above
    BOOL            autoCyclesTransitionStyle;  // set if we should automatically cycle our transitionStyle
    CIImage         *inputShadingImage;         // an environment-map image that the transition filter may use in generating the transition effect
    CIImage         *inputMaskImage;            // a mask image that the transition filter may use in generating the transition effect
}

まず awakeFromNib。ここではマスク画像など共通に使われる CIImageインスタンスを準備している。

- (void)awakeFromNib {
       :
    inputShadingImage = [[CIImage alloc] initWithBitmapImageRep:shadingBitmap];
       :
    inputMaskImage = [[CIImage alloc] initWithBitmapImageRep:maskBitmap];
}

続いて updateSubviewsTransition。ここはトランジションの切り替えで呼ばれる。

- (void)updateSubviewsTransition {
    NSRect rect = [self bounds];
    NSString *transitionType = nil;
    CIFilter *transitionFilter = nil;
    CIFilter *maskScalingFilter = nil;
    CGRect maskExtent;

    switch (transitionStyle) {
        case SlideshowViewFadeTransitionStyle:
            transitionType = kCATransitionFade;
            break;
            :
        case SlideshowViewRippleTransitionStyle:
        default:
            transitionFilter = [[CIFilter filterWithName:@"CIRippleTransition"] retain];
            [transitionFilter setDefaults];
            [transitionFilter setValue:[CIVector vectorWithX:NSMidX(rect) Y:NSMidY(rect)] forKey:@"inputCenter"];
            [transitionFilter setValue:[CIVector vectorWithX:rect.origin.x Y:rect.origin.y Z:rect.size.width W:rect.size.height] forKey:@"inputExtent"];
            [transitionFilter setValue:inputShadingImage forKey:@"inputShadingImage"];
            break;

CIRippleTransitionの設定が一通り行われる。続いて Core Annimation 設定。

    // Construct a new CATransition that describes the transition effect we want.
    CATransition *transition = [CATransition animation];
    if (transitionFilter) {
        // We want to build a CIFilter-based CATransition.  When an CATransition's "filter" property is set, the CATransition's "type" and "subtype" properties are ignored, so we don't need to bother setting them.
        [transition setFilter:transitionFilter];
    } else {
        // We want to specify one of Core Animation's built-in transitions.
        [transition setType:transitionType];
        [transition setSubtype:kCATransitionFromLeft];
    }

    // Specify an explicit duration for the transition.
    [transition setDuration:1.0];

    // Associate the CATransition we've just built with the "subviews" key for this SlideshowView instance, so that when we swap ImageView instances in our -transitionToImage: method below (via -replaceSubview:with:).
    [self setAnimations:[NSDictionary dictionaryWithObject:transition forKey:@"subviews"]];

この @"subviews"がよくわからない。



そして transitionToImage: 。このメソッドは SlidshowWindowController から呼出される。画像が次々と変わる時に transitionToImage: が呼出される。

- (void)transitionToImage:(NSImage *)newImage {
     :
     :
    // Create a new NSImageView and swap it into the view in place of our previous NSImageView.  This will trigger the transition animation we've wired up in -updateSubviewsTransition, which fires on changes in the "subviews" property.
    NSImageView *newImageView = nil;
    if (newImage) {
        newImageView = [[NSImageView alloc] initWithFrame:[self bounds]];
        [newImageView setImage:newImage];
        [newImageView setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
    }
    if (currentImageView && newImageView) {
        [[self animator] replaceSubview:currentImageView with:newImageView];
    } else {
        if (currentImageView) [[currentImageView animator] removeFromSuperview];
        if (newImageView) [[self animator] addSubview:newImageView];
    }
 [currentImageView release];
    currentImageView = newImageView;
}

渡された画像（NSImage）を表示する NSImageViewを作成し、トランジションをかける。っと見えるのだがイマイチ理解できない。

[[self animator] replaceSubview:currentImageView with:newImageView];

この辺りがトランジションのアニメーション処理の肝だろうか。