Re: Octave-handled graphics

Unfortunately, my code contains only minor differences from jwe's 
handle-graphics.tgz so far (I'm a better document writer than coder).

I can give a general summary, and feel free to ask questions so that 
hopefully I can improve the summary to the form that it will be a good 
document for backend writers to use.  I will post this on the wiki with 
suggestions welcome on how to make it better.

To make a backend for octave, we will use a method called dispatching. 
You will be responsible for creating a function called __drawnow_<backend 
name>__ (e.g. __drawnow_gnuplot__) that will draw the current figure 
object.  This will be dispatched over __drawnow__.  The drawing has 
several steps:

* Determine the current figure.
   * either
     fignum = get(0, "currentfigure");
     or
     fignum = gcf()
* Get the information from that figure.
   * figdata = get(fignum);
* Draw the figure window according to the parameters from that figure.
* Draw the children of the figure
   * something like the following code
     for i = 1:length(figdata.children)
       kid = figdata.children(i);
       drawchild(kid);
     endfor
* Some child types will have their own children (axes, groups, etc.)  They
   will need to be drawn in a similar method.

Bill

On Mon, 1 May 2006, Robert S. Weigel wrote:

> Dear Bill,
>
> I am looking for a write-up or paragraph that describes the steps
> needed to develop and Octave-handled graphics backend.  Perhaps using
> gnuplot as an example?  The audience is a C++ programmer who has never
> used Octave or Matlab.  Your wiki page is a great starting point, but
> we are getting hung up on the part where we try to figure out what to
> do with the code in handle-graphics.tgz.  A concrete example with
> something I understand, such as gnuplot, would help me spec the
> project out.
>
> Project?  I am trying to get an estimate for the time required to do this,
> either as part of a new project or a proposed project.
>
> Thanks,
>
> Bob Weigel
>

-- 
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