FunkyOverlayWindow/TransparentButtonCell.m

/*
     File: TransparentButtonCell.m 
 Abstract: This NSButtonCell subclass knows how to draw the button frame transparent, while
 the actual content stays non-transparent.  It does this by rendering the button
 into an NSImage, drawing the image with transparancy back into the control view,
 and then drawing the button contents again. 
  Version: 1.1 
  
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 */
 
 
#import "TransparentButtonCell.h"
 
@implementation TransparentButtonCell
 
- (void)drawWithFrame:(NSRect)cellFrame inView:(NSView *)controlView
{
    NSImage *alphaImage;
    
    NSRect alphaImageRect = { NSZeroPoint, cellFrame.size };
    
    alphaImage = [[NSImage alloc] initWithSize:alphaImageRect.size];
    [alphaImage setFlipped:[controlView isFlipped]];
    [alphaImage lockFocus];
    
    BOOL wasEnabled = [self isEnabled];
    [self setEnabled:YES];
        // Draw the default button cell frame in the image
    [super drawWithFrame:alphaImageRect inView:controlView];
    [self setEnabled:wasEnabled];
    
    [alphaImage unlockFocus];
 
        // Draw the image with partial transparency into the control view
    [alphaImage drawAtPoint:cellFrame.origin fromRect:alphaImageRect operation:NSCompositeSourceOver fraction:0.75];
        // Draw the contents of the interior button image again, this time without transparency
    [self drawInteriorWithFrame:cellFrame inView:controlView];
    
    [alphaImage release];
}
 
@end