[gtkada] Plotcanvas question

[Manuel Op de Coul]

My plots also broke doing the upgrade. It almost works now
but still one small problem: when a plot is redrawn, the
old plot doesn't disappear anymore, where it did in the past.
So then the old and new plot are mixed together.

In the redraw routine I create a plot, add it to the canvas,
etc. Another change I made was to call Paint and Refresh on
the canvas, because otherwise a Show_All on the dialog also
didn't show the plot anymore like in 1.2.

But how can I clear the canvas of the old plot?

In the spec of Gtk.Extra.Plot_Canvas.Add_Plot it says

   Plot becomes the new active plot, and its associated pixmap
   becomes the Plot_Canvas itself.

But if it becomes the Plot_Canvas itself, how come the old
plot is still visible when a new one replaces it?

Manuel