A UISlider subclass for iOS7 that respects alignmentRectInsets on custom thumb images

AlignmentRectRespectingSlider.h

@interface AlignmentRectRespectingSlider : UISlider
@end

AlignmentRectRespectingSlider.m

@implementation AlignmentRectRespectingSlider

- (CGRect)thumbRectForBounds:(CGRect)bounds trackRect:(CGRect)rect value:(float)value {
  UIImage* image = self.currentThumbImage;
  UIEdgeInsets insets = image.alignmentRectInsets;
  CGFloat fullWidth = image.size.width;
  CGFloat fullHeight = image.size.height;
  CGFloat coreWidth = fullWidth - insets.left - insets.right;
  CGFloat coreHeight = fullHeight - insets.top - insets.bottom;
  CGFloat usableTrackWidth = rect.size.width - coreWidth;
  CGFloat offset = usableTrackWidth * value;
  
  CGRect thumbRect = CGRectMake(rect.origin.x - insets.left + offset,
                                rect.origin.y + 0.5f * rect.size.height - 0.5f * coreHeight - insets.top,
                                fullWidth, fullHeight);
  return thumbRect;
}

@end