Helpers for Quartz chapter

Constants.m

#define RANGE (700.0f)
// RANGE is the range of values that are OK

#define B_MARGIN (10.0f)
// B_MARGIN is the bottom margin in points

#define T_MARGIN (10.0f)
// T_MARGIN is the top margin in points

#define H_GAP (10.4f)
// H_GAP is the gap between the bars and side margins

ReportRenderer.m

- (id)initWithPersons:(NSArray *)persons
{
    self = [super init];
    if (self) {
        self.persons = persons;
    }
    return self;
}

- (void)drawInContext:(CGContextRef)ctx
               bounds:(CGRect)bounds
{
    NSLog(@"Drawing in %@", NSStringFromCGRect(bounds));
    
    CGColorSpaceRef cs = CGColorSpaceCreateDeviceRGB();
    
    CGFloat blackRGBA[] = { 0, 0, 0, 1 };
    CGColorRef black = CGColorCreate(cs, blackRGBA);

    CGFloat whiteRGBA[] = { 1, 1, 1, 1 };
    CGColorRef white = CGColorCreate(cs, whiteRGBA);
    
    CGContextSetStrokeColorWithColor(ctx, black);
    CGContextSetLineWidth(ctx, 1);
    
    CGContextSetFillColorWithColor(ctx, white);
    
    float minY = CGRectGetMinY(bounds) + B_MARGIN;
    float maxY = CGRectGetMaxY(bounds) - T_MARGIN;
    float increment = (maxY - minY) / RANGE;
    
    int personCount = [self.persons count];
    float totalHGaps = (personCount + 2) * H_GAP;
    float barWidth = (bounds.size.width - totalHGaps) / personCount;
    
    // Draw the bars
    CGRect barRect;
    barRect.size.width = barWidth;
    barRect.origin.y = minY;
    
    int idx=0;
    for (BNRPerson *person in self.persons) {
        barRect.origin.x = bounds.origin.x + H_GAP + (barWidth + H_GAP) * idx;
        barRect.size.height = increment * person.sales;

        CGPathRef barPath = CGPathCreateWithRect(barRect, NULL);
        CGContextAddPath(ctx, barPath);
        CGContextFillPath(ctx);
        
        // Fill path clears the current path, so add it again
        CGContextAddPath(ctx, barPath);
        CGContextStrokePath(ctx);
        CGPathRelease(barPath);
        
        idx++;
    }
    
    CGColorRelease(white);
    CGColorRelease(black);
    
    CGColorSpaceRelease(cs);
}

- (void)drawLayer:(CALayer *)layer
        inContext:(CGContextRef)ctx
{
    [self drawInContext:ctx bounds:layer.bounds];
}