title: Custom NSScroller issues
body: <p>I'm trying to subclass NSScroller in order to draw my own scroller knob. To do this, I've subclassex NSScrollView and usex the following code to instantiate my custom NSScrollers:</p>
  
  <pre><code>- (void)awakeFromNib;
  {
      NSRect horizontalScrollerFrame = [[self horizontalScroller] frame];
      NSRect verticalScrollerFrame = [[self verticalScroller] frame];
      NSString *scrollBarVariant = [[[NSUserDefaults standardUserDefaults] persistentDomainForName:NSGlobalDomain] valueForKey:@"AppleScrollBarVariant"];
  
      if (![scrollBarVariant isEqualToString:@"DoubleBoth"]) {
          [self setVerticalScroller:[[[TRScroller alloc] initWithFrame:verticalScrollerFrame] autorelease]];
          [self setHorizontalScroller:[[[TRScroller alloc] initWithFrame:horizontalScrollerFrame] autorelease]];
      }
  }
  </code></pre>
  
  <p>This works and my NSScrollers display correctly. But I'm occasionally seeing rendering issues upon first loading my application. Within Interface Builder I have laid out a number of NSScrollViews with their scrollbars set to hide automatically. The issue I'm seeing is that when the application first loads, the scrollbar backgrounds are rendered across the NSScrollViews contents.</p>
  
  <p><a href="http://www.freeimagehosting.net/uploads/1d3fc75db8.png" rel="nofollow noreferrer">alt text http://www.freeimagehosting.net/uploads/1d3fc75db8.png</a></p>
  
  <p>I believe this is because I instantiate my NSScroll subclass (TRSubclass) via awakeFromNib, which means that the scrollbars are given the frame of the NSScrollView before it is automatically resized to meet the windows saved location and size (in other words, it's using the frame that's assigned by default within Interface Builder). What's the best way around this?</p>
  
  <p>I've tried forcing the NSScrollView to redisplay (using setNeedsDisplay: and display:) but with no luck. Has anyone else come across a similar issue? </p>