[Tioga-users] Marker outside plot area

[Bill Paxton]

Hi Edwin,

On May 19, 2008, at 7:42 AM, Edwin wrote:

> I have a (log-log) plot where I want to plot one point/marker  
> slightly outside the main plot area (below the xaxis). Is this  
> possible? Alternatively, is it possible to plot the x-axis at any  
> location instead of just TOP BOTTOM, AT_Y_ORIGIN?

Thanks to Vincent, you should be able to put the x-axis anywhere  
you'd like.  Since he knows more about it that I do, I'm going to let  
him provide the details.

Concerning your first question: we need to talk about clipping!   
Here's the tioga show_plot routine:

     def show_plot(bounds=nil,&cmd)
         trace_cmd_one_arg(@enter_show_plot_function,  
@exit_show_plot_function, bounds) {
             set_bounds(bounds)
             context { clip_to_frame; cmd.call(self) }
             show_plot_box
         }
     end

The show_plot command argument is called inside a context after first  
doing clip_to_frame.
That keeps the plot graphics inside the bounds, which is good. ; - )   
Except for cases like yours!
What you'd like to do is (perhaps) temporarily turn off the clipping  
so you can write your marker outside of the plot area.
However, in PostScript/PDF there is no way to enlarge a clipping  
region; you can only reduce it.

So what might work instead would be something like this:

     def my_show_plot(bounds=nil,&cmd)
         my_enter_show_plot_function(bounds)
         set_bounds(bounds)
         context { clip_to_frame; cmd.call(self) }
         context { my_unclipped_stuff }
         show_plot_box
         my_exit_show_plot_function (bounds)
     end

If you decide to give this approach a try, please let me know how it  
goes!

Cheers,
Bill

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