[Drawkit] Minor fix for text selection in DrawDemo

[Brad Larson]

I had lifted some code from the DrawDemo application to add an  
inspector to our drawing program when I noticed that one of the text  
cells wasn't properly responding to mouse selection of the text.  In  
the drawing layer inspector, the custom  
RSVerticallyCenteredTextFieldCell is used to provide vertically  
aligned text within the layer table.  However, the hit testing in that  
custom cell is still using the traditional top-aligned text location,  
which causes some frustration when you're trying to edit the cell.

To fix this, you can add the following to  
RSVerticallyCenteredTextFieldCell's implementation:

- (NSUInteger)hitTestForEvent:(NSEvent *)event inRect: 
(NSRect)cellFrame ofView:(NSView *)controlView
{
	NSRect newRect = [super drawingRectForBounds:cellFrame];

	// Get our ideal size for current text
	NSSize textSize = [self cellSizeForBounds:cellFrame];
	
	// Center that in the proposed rect
	float heightDelta = newRect.size.height - textSize.height;	
	if (heightDelta > 0)
	{
		newRect.size.height -= heightDelta;
		newRect.origin.y += (heightDelta / 2);
	}
	
	return [super hitTestForEvent:event inRect:newRect ofView:controlView];
}

This is not strictly DrawKit-related, but it does affect the DrawDemo  
sample application.

______________________
Brad Larson
SonoPlot, Inc.
3030 Laura Lane, Suite 120
Middleton, WI 53562