- (float) splitView:(NSSplitView *)sender constrainMinCoordinate:(float)proposedMin ofSubviewAt:(int)offset {
  if(offset == 0) {
    return MIN_LEFT_PANEL_W;
  } else {
    return 0; //this never happens so....
  }
}

- (void) splitView:(NSSplitView *)sender resizeSubviewsWithOldSize:(NSSize)oldSize {
  // http://www.wodeveloper.com/omniLists/macosx-dev/2003/May/msg00261.html
  
  // grab the splitviews
    NSView *left = [[sender subviews] objectAtIndex:0];
    NSView *right = [[sender subviews] objectAtIndex:1];
  
    float dividerThickness = [sender dividerThickness];
  
  // get the different frames
    NSRect newFrame = [sender frame];
    NSRect leftFrame = [left frame];
    NSRect rightFrame = [right frame];
  
  // change in width for this redraw
  int  dWidth  = newFrame.size.width - oldSize.width;
  
  // ratio of the left frame width to the right used for resize speed when both panes are being resized
  float rLeftRight = (leftFrame.size.width - MIN_LEFT_PANEL_W) / rightFrame.size.width;

  // resize the height of the left
    leftFrame.size.height = newFrame.size.height;
    leftFrame.origin = NSMakePoint(0,0);
  
  // resize the left & right pane equally if we are shrinking the frame
  // resize the right pane only if we are increasing the frame
  // when resizing lock at minimum width for the left panel
  if(leftFrame.size.width <= MIN_LEFT_PANEL_W && dWidth < 0) {
    rightFrame.size.width += dWidth;
  } else if(dWidth > 0) {
    rightFrame.size.width += dWidth;
  } else {
    leftFrame.size.width += floor(dWidth * rLeftRight);
    rightFrame.size.width += ceil(dWidth * (1 - rLeftRight));
  }

    rightFrame.size.width = newFrame.size.width - leftFrame.size.width - dividerThickness;
    rightFrame.size.height = newFrame.size.height;
    rightFrame.origin.x = leftFrame.size.width + dividerThickness;

    [left setFrame:leftFrame];
    [right setFrame:rightFrame];
}