dropshadow.m

-(void)drawInContext:(CGContextRef)myContext {	
    CGContextSaveGState(myContext);// 6
	
	CGFloat potentialFlip = 1.0;
	CGFloat shadowBlur = 4;
	CGFloat shadowOffset = 4;
	CGFloat shadowOffsetNeg = shadowOffset * -1.0;
	CGFloat x = self.bounds.origin.x + shadowOffset;
	CGFloat y = self.bounds.origin.y + shadowOffset;
	CGFloat wd = self.bounds.size.width - (shadowOffset * 2);
	CGFloat ht = self.bounds.size.height - (shadowOffset * 2);
	
	
	NSString *reqSysVer = @"3.2";
	NSString *currSysVer = [[UIDevice currentDevice] systemVersion];
	
	//NSLog(@"current os version: %@", currSysVer);
	if ([currSysVer compare:reqSysVer options:NSNumericSearch] == NSOrderedAscending)
	{
		//NSLog(@"on ios < 3.2, flipping vertical offset");
		// see http://github.com/facebook/three20/issues/closed?authenticity_token=81bd5d471e7545bb0ed1f361249bb734fbf5a44b#issue/158
		potentialFlip = -1.0;
	}
	
	
	// left side and top
	CGContextSetShadow (myContext, CGSizeMake (shadowOffsetNeg,  shadowOffsetNeg * potentialFlip), shadowBlur); // 7
    CGContextFillRect (myContext, CGRectMake (x, y, wd, ht));
	
	
	// right side and top
	CGContextSetShadow (myContext, CGSizeMake (shadowOffset,  shadowOffsetNeg * potentialFlip), shadowBlur); // 7	
    CGContextFillRect (myContext, CGRectMake (x + wd - shadowOffset, y, shadowOffset, ht));
	
	// missing top cube on the right
	CGContextSetShadow (myContext, CGSizeMake (0,  shadowOffsetNeg * potentialFlip), shadowBlur); // 7	
    CGContextFillRect (myContext, CGRectMake (x + wd - shadowOffset, y, shadowOffset, ht));
	
	// bottom left
	CGContextSetShadow (myContext, CGSizeMake (shadowOffsetNeg,  shadowOffset * potentialFlip), shadowBlur); // 7	
    CGContextFillRect (myContext, CGRectMake (x, y + ht - shadowOffset, wd, shadowOffset));
	
	//missing cube on the bottom left
	CGContextSetShadow (myContext, CGSizeMake (shadowOffsetNeg,  0), shadowBlur); // 7	
    CGContextFillRect (myContext, CGRectMake (x, y + ht - shadowOffset, shadowOffset, shadowOffset));
	
	//bottom right corner
	CGContextSetShadow (myContext, CGSizeMake (shadowOffset,  shadowOffset * potentialFlip), shadowBlur); // 7	
    CGContextFillRect (myContext, CGRectMake (x + wd - (shadowOffset * 2), y + ht - (shadowOffset * 2), shadowOffset * 2, shadowOffset * 2));
    	
    CGContextRestoreGState(myContext);
}