I have a class which implements guide lines as a layer of a drawing. That’s all fine, debugged, working. I would like to be able to create guides in the manner of Photoshop et. al. by dragging them off the ruler. So I have a scrollview with NSRulerViews showing, and my main view is a client of both rulers. I pick up the client message - (void) rulerView:(NSRulerView) aRulerView handleMouseDown:(NSEvent) theEvent; , which allows me to detect the initial click in the ruler. I can use this event to create the guideline, but what now? I want to drag down into the main area of the view and have the guide track the mouse. My guide object does that part as long as I can get a mouseDragged event to it, but I can’t see how to get a mouseDragged event out of the NSRulerView. Any idea how to do this?

OK, I figured it out myself - it’s easy. All I had to do was to implement my own short modal tracking loop as long as I don’t see a mouseUp event. This loop keeps control until I stop dragging the guide. Here’s my code, based on the example in the cocoa docs “Handling Mouse Events in Views”:

• (void) rulerView:(NSRulerView) aRulerView handleMouseDown:(NSEvent) theEvent { // this is our cue to create a new guide, if the drawing has a guide layer.

  GCGuideLayer* gl = self drawing] guideLayer];

  if ( gl ) { // add h or v guide depending on ruler orientation

    [[NSPoint p = [self convertPoint:[theEvent locationInWindow] fromView:nil];
  	
    if ([aRulerView orientation] == NSVerticalRuler)
        [gl createVerticalGuideAndBeginDraggingFromPoint:p];
    else
        [gl createHorizontalGuideAndBeginDraggingFromPoint:p];
  
    [gl mouseDown:theEvent inView:self];
  	
    BOOL keepOn = YES;
   
    while (keepOn)
    {
        theEvent = self window] nextEventMatchingMask: [[NSLeftMouseUpMask | NSLeftMouseDraggedMask];
   
        switch ([theEvent type])
        {
            case NSLeftMouseDragged:
                [gl mouseDragged:theEvent inView:self];
                break;
  			
            case NSLeftMouseUp:
                [gl mouseUp:theEvent inView:self];
                keepOn = NO;
                break;
        default:
                /* Ignore any other kind of event. */
                break;
        }
    }   } }