Re: [Matplotlib-users] RE : Re: transformations

[John H. <jd...@gm...>]

On 2/6/07, Nicolas <nic...@ya...> wrote:
> Thanks a lot for your reply.

You're welcome.  Please keep correspondence on the list so others an
contribute and benefit.

> I read this story of lazy value in the doc, but I didn't understand the link
> with the the Affine function.

All of the matplotlib transformations are by reference.  We want to be
able to do
build the transform like so:

  a = someval
  t  = Affine(a,b,c,d,e,f)

and then later in the code do

  a.set(23)

and have the transformation automatically updated.  You can't do this
if a is a scalar value (eg a float) so we have a custom class Value
which stores a pointer to a float.  When you do

  a = Value(23)
  t  = Affine(a,b,c,d,e,f)

and later do a.set(23) then t will be updated.  We also support
arithmetic on Values, so you can do

  z = Value(3)
  x = Value(2)
  t  = Affine(z*x,b,c,d,e,f)

and later if you do

  x.set(4)

then the transform will be updated to have the value a=12

>From a user perspective, it means you need do do

  t = Affine(Value(a), Value(b), .....)

if a and b are floats.  This is what the make_affine function that I
posted does.

> Additionnaly, I noticed that antialiasing doesn't seem to work anymore in
> function pie with recent (ie. 0.87.5) version of matplotlib on WxAgg (?)

Odd, I see that too.  Haven't been able to pinpoint the problem yet...

JDH