ExampleCALayerDelegate.m

//
// File:       ExampleCALayerDelegate.m
//
// Abstract:   A sample delegate for a CALayer that draws random content into the layer.
//
// Version:    1.0
//
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#import "ExampleCALayerDelegate.h"
 
@implementation ExampleCALayerDelegate
 
static CGFloat randomFloat()
{
    CGFloat f = (rand() % RAND_MAX) / (float)(RAND_MAX);
    return f;
}
 
static CGPoint randomPointInBounds(CGRect bounds)
{
    CGFloat x = randomFloat() * bounds.size.width + bounds.origin.x;
    CGFloat y = randomFloat() * bounds.size.height + bounds.origin.y;
    return CGPointMake(x, y);
}
 
-(void)drawLayer:(CALayer *)layer inContext:(CGContextRef)context
{
    // We aren't interested in the actual content of this layer, we just want to draw something.
    // Towards that end, we'll fill the content with a random color,
    // then fill a randomly generated polygon.
    
    CGRect bounds = CGContextGetClipBoundingBox(context);
    CGContextSetRGBFillColor(context, randomFloat(), randomFloat(), randomFloat(), 1.0);
    CGContextFillRect(context, bounds);
    
    int sides = (random() % 18) + 1;
    CGPoint p = randomPointInBounds(bounds);
    CGContextMoveToPoint(context, p.x, p.y);
    for(int i = 0; i < sides; ++i)
    {
        p = randomPointInBounds(bounds);
        CGContextAddLineToPoint(context, p.x, p.y);
    }
    CGContextClosePath(context);
    CGContextSetRGBFillColor(context, randomFloat(), randomFloat(), randomFloat(), 1.0);
    CGContextEOFillPath(context);
}
 
@end