Re: [pyGEF-develop] Using enthought.kiva as rendering backend

[<pyg...@li...>]

pyg...@li... wrote:
> Hi there
> 
> Just to let you know that we have one new member, Louis Jordaan.
> He is one of my students and will be doing his final year engineering
> project for the next five to six months. A large portion of his work is to
> make pyGEF usable

Great news -- I'm looking forward to the results!

> I have been looking at Kiva for the last day or so. Have any of you ever
> used it?

No

> Read about it?

Yes.

> As far as I could figure out it uses agg as a
> renderer/back-end.

Well, it's supposed to a multi-back-end thing, like many, but Agg is the 
most-used one. I think the wx back-end for instance, renders with Agg, 
then blits to wx -- like Matplotlib wxAgg.

It's modeled after DisplayPDF, so it should work with on OS-X, and I"d 
think the PDF back-end would be pretty simple! Having a PDF option sure 
would be nice.

 > Which you have previously suggested agg.

That may have been me -- it does have very nice output, and it's 
reported to be very fast.

> It looks like it's rendering is much, MUCH faster than using the GC directly

I'm getting more disappointed with GC's performance. But does it support 
everything you need?

> 1. Can or should pyGEF use Kiva as its primary backend?
> 2. In the current version of pyGEF I use a Plotter class to draw my graphic
> objects. This Plotter Interface class (abstraction layer) allows for the use
> of multiple rendering back-ends. The problem is that an API for this Plotter
> Interface needs to be defined. I would appreciate suggestions, with special
> considerations for that fact that pyGEF must be usable as a base for a SVG
> type graphic drawing tool.

Have you seen any of Chris Mellon's work with a wxPython SVG renderer? 
Search the wxPython mailing list for more info.


> I'm trying to teach +-480 first year students to program

yow! Using Python, I hope!

> Bill, I saw that enthought has a very basic affine transform module in kiva
> (all python), 

Are you sure. I see this on the Wiki:

"""
AffineMatrix:

(kiva_affine_matrix.h and affine_matrix.i) All of the following member 
functions modify the instance on which they are called:

     * __init__(v0, v1, v2, v3, v4, v5) or __init__()
     * reset() # sets this matrix to the identity
     * multiply(AffineMatrix) # multiples this matrix by another
     * invert() # sets this matrix to the inverse of itself
     * flip_x() # mirrors around X
     * flip_y() # mirrors around Y
     * scale() -> float # returns the average scale of this matrix
     * determinant() -> float # returns the determinant

The following factory methods are available in the top-level "agg" 
namespace to create specific kinds of AffineMatrix instances:

     * translation_matrix(float X, float Y)
     * rotation_matrix(float angle_in_radians)
     * scaling_matrix(float x_scale, float y_scale)
     * skewing_matrix(float x_shear, float y_shear)

FontType

"""
This makes it look like there is a C/C++ implementation of some sort.

-Chris



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