Re: [matplotlib-devel] refactoring the backend drawing methods

[Paul B. <ba...@st...>]

John Hunter wrote:
> 
> I've begin to address some of these concerns with a new backend method
> "draw_markers".  Currently the backend has too many drawing methods,
> and this is yet another one.  My goal is to define a core set, many
> fewer than we have today, and do away with most of them.  Eg
> draw_pixel, draw_line, draw_point, draw_rectangle, draw_polygon, can
> all be replaced by draw_path, with paths comprised solely of MOVETO,
> LINETO and (optionally) ENDPOLY.

Though the idea of having a minimal set of draw methods is esthetically 
appealing, in practice having to reuse these few commonly drawn methods 
  to construct simple compound objects can become cumbersome and 
annoying.  I would suggest taking another look at Adobe's PDF language 
and Apple's Quartz (or display PDF).  It is iteresting to see that each 
new version adds one or two new draw methods, e.g. rectangle and 
rectangles, to make it easier and faster to draw these common paths. 
I'm guessing these new methods are based on copius experience.

While you are at it, I would suggest looking at the clipping issue.  As 
in PS and PDF, a path can be used as a clipping region.  This allows the 
backend, in PS and PDF, to do the clipping for you, which can make the 
code simpler and also faster.  Clipping using arbitrary paths may 
currently be an issue for AGG, but in my opinion, it is something that 
AGG will eventually have to come to grips with.

Just my $0.01.

  -- Paul

-- 
Paul Barrett, PhD      Space Telescope Science Institute
Phone: 410-338-4475    ESS/Science Software Branch
FAX:   410-338-4767    Baltimore, MD 21218