/*

 Copyright (C) 2017 Apple Inc. All Rights Reserved.

 See LICENSE.txt for this sample’s licensing information

 Abstract:

 This view is backed by a CATiledLayer into which the PDF page is rendered into.

 */

#import "TiledPDFView.h"

#import <QuartzCore/QuartzCore.h>

@implementation TiledPDFView

// Create a new TiledPDFView with the desired frame and scale.

- (id)initWithFrame:(CGRect)frame scale:(CGFloat)scale

{

    self = [super initWithFrame:frame];

    if ( self ) {

        CATiledLayer *tiledLayer = (CATiledLayer *)[self layer];

        /*

         levelsOfDetail and levelsOfDetailBias determine how the layer is rendered at different zoom levels. This only matters while the view is zooming, because once the the view is done zooming a new TiledPDFView is created at the correct size and scale.

         */

        tiledLayer.levelsOfDetail = 4;

        tiledLayer.levelsOfDetailBias = 3;

        tiledLayer.tileSize = CGSizeMake(512.0, 512.0);

        self.myScale = scale;

        self.layer.borderColor = [UIColor lightGrayColor].CGColor;

        self.layer.borderWidth = 5;

    }

    return self;

}

// Clean up.

- (void)dealloc

{

    if ( self.pdfPage != NULL ) CGPDFPageRelease( self.pdfPage );

}

// The layer's class should be CATiledLayer.

+ (Class)layerClass

{

    return [CATiledLayer class];

}

// Set the CGPDFPageRef for the view.

- (void)setPage:(CGPDFPageRef)newPage

{

    if ( self.pdfPage != NULL ) CGPDFPageRelease( self.pdfPage );

    if ( newPage != NULL ) self.pdfPage = CGPDFPageRetain( newPage );

}

// Draw the CGPDFPageRef into the layer at the correct scale.

- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)context

{

    // Fill the background with white.

    CGContextSetRGBFillColor(context, 1.0, 1.0, 1.0, 1.0);

    CGContextFillRect(context, self.bounds);

    // Print a blank page and return if our page is null.

    if ( _pdfPage == NULL )

    {

        return;

    }

    // save the cg state

    CGContextSaveGState(context);

    // Flip the context so that the PDF page is rendered right side up.

    CGContextTranslateCTM(context, 0.0, self.bounds.size.height);

    CGContextScaleCTM(context, 1.0, -1.0);

    // Scale the context so that the PDF page is rendered at the correct size for the zoom level.

    CGContextScaleCTM(context, self.myScale, self.myScale);

    // draw the page, restore and exit

    CGContextDrawPDFPage(context, self.pdfPage);

    CGContextRestoreGState(context);

}

@end