gistfile1.m

- (void)setCurrentScreen:(Screen)aScreen
{ 
  if (aScreen == currentScreen)
    return;

  [currentScreen removeFromSuperview];
  currentScreen = aScreen;
  if (currentScreen) {
    [screenBorder addSubview:currentScreen];
  }   
  
  [self sizeToFit];
}

- (void)sizeToFit
{ 
   if (!currentScreen) {
     [docView setFrameSize:CGSizeMakeCopy([self frame].size);
     [screenBorder setFrameSize:CGSizeMakeCopy([self frame].size);
     return;
   }

   var currentScreenSize = [currentScreen frame].size;

   var newWidth = Math.max([self frame].size.width, currentScreenSize.width),
       newHeight = Math.max([self frame].size.height, currentScreenSize.height);

   [docView setFrameSize:CGSizeMake(newWidth,newHeight)];

   [screenBorder setFrameSize:CGSizeMake(currentScreenSize.width + 4, currentScreenSize.height + 4)];  
   [screenBorder setFrameOrigin:CGPointMake(CPRectGetWidth([docView frame])/2.0 - CPRectGetWidth([screenBorder frame])/2.0, CPRectGetHeight([docView frame])/2.0 - CPRectGetHeight([screenBorder frame])/2.0)];

    [currentScreen setFrameOrigin:CGPointMake(2,1)];    
  } 
}