First the good news: The Tkinter/OpenGL based version of Chaco/Kiva is =
very near completion.

The major remaining work items are:

1) Convert Eric's wxPython based FreeType Kiva code to work with the =
OpenGL based version of Kiva.

2) Improve overall performance dramatically.

Some people voiced a concern that the wxPython based version of Chaco =
seems a little slow. Well, compared to the current OpenGL version, it =
hums like a well oiled machine :-(

Hence the request for help...

Most of the performance issues with the OpenGL version of Chaco have to =
do with interactive operations, like drawing the cursor crosshair lines =
or the graph and axis selection regions.

In the wxPython version, we maintain an off-screen bitmap of the =
PlotWindow contents and either xor the cursor or selection regions into =
the screen or blit the off-screen bitmap onto the screen (e.g. to =
refresh the window when a region of the PlotWindow is exposed).

Being fairly inexperienced with OpenGL I have not been able to find a =
way to do something equivalent in OpenGL:

- The OpenGL 'overlay' buffers do not appear to be supported by the =
version of 'togl' supplied with the current PyOpenGL package.=20

- Trying to do a glReadPixels(...) call to read the contents of the =
OpenGL buffer seems to take about a second on a > 1 GHz processor (hardly =
useful for interactive work).

So the question is:

Does anyone know how to efficiently 'rubberband' things in OpenGL?=20

If the asnwer is to use the overlay buffer, does anyone know how to get =
it to work with a Tkinter based OpenGL widget?

Thanks in advance for any help...

Dave Morrill