/*

 Copyright (C) 2018 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 IKImageBrowserView's background CALayer subclass for drawing a custom background image.

 */

#import "ImageBrowserBackgroundLayer.h"

@implementation ImageBrowserBackgroundLayer

// -------------------------------------------------------------------------

//    init

// -------------------------------------------------------------------------

- (instancetype)init

{

    self = [super init];

    if (self != nil)

    {

        // Needs to redraw when bounds change.

        [self setNeedsDisplayOnBoundsChange:YES];

    }

    return self;

}

// -------------------------------------------------------------------------

//    actionForKey:

//

//    Always return nil, to never animate.

// -------------------------------------------------------------------------

- (id<CAAction>)actionForKey:(NSString *)event

{

    return nil;

}

// -------------------------------------------------------------------------

//    drawInContext:

//

//    Draw a metal background that scrolls when the image browser scroll.

// -------------------------------------------------------------------------

- (void)drawInContext:(CGContextRef)context

{

    // Retreive bounds and visible rect.

    NSRect visibleRect = self.owner.visibleRect;

    NSRect bounds = self.owner.bounds;

    // Retreive background image from our bundle.

    NSURL *urlForImage =

        [[NSBundle mainBundle] URLForResource:@"metal_background" withExtension:@"tif"];

    CGImageSourceRef imageSource = CGImageSourceCreateWithURL((CFURLRef)urlForImage, NULL);

    if (imageSource != nil)

    {

        CGImageRef image = CGImageSourceCreateImageAtIndex(imageSource, 0, NULL);

        if (image != nil)

        {

            float width = (float) CGImageGetWidth(image);

            float height = (float) CGImageGetHeight(image);

            // Compute coordinates to fill the view.

            float left, top, right, bottom;

            top = bounds.size.height - NSMaxY(visibleRect);

            top = fmod(top, height);

            top = height - top;

            right = NSMaxX(visibleRect);

            bottom = -height;

            // Tile the image and take in account the offset to 'emulate' a scrolling background.

            for (top = visibleRect.size.height-top; top>bottom; top -= height)

            {

                for (left = 0; left < right; left += width)

                {

                    CGContextDrawImage(context, CGRectMake(left, top, width, height), image);

                }

            }

            CFRelease(image);

        }

        CFRelease(imageSource);

    }

}

@end