title: Custom NSButton with semi-transparent background
body: <p>I'm trying to create a custom NSButton with a 50% opaque black background and white text. To do this I've subclassed NSButton and overloaded DrawRect:</p>
  
  <pre><code>- (void) drawRect:(NSRect)dirtyRect
  {
  
      [self setBordered:NO];
  
      //REMED since it has same effect as NSRectFill below
      //[[self cell] setBackgroundColor:[NSColor colorWithCalibratedRed:0 green:0 blue:0 alpha:0.2]];
  
      NSColor* backgroundColor = [NSColor colorWithCalibratedWhite:0 alpha:0.3f];
      [backgroundColor setFill];
      NSRectFill(dirtyRect);
  
      [super drawRect:dirtyRect];
  }
  </code></pre>
  
  <p>The white text appears fine but the button's background is always 100% opaque. The alpha value is not interpreted.</p>
  
  <p>Any ideas? Thanks!</p>