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Move axisartist towards using standard Transforms. #20207

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Merged
merged 2 commits into from
May 17, 2021

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anntzer
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@anntzer anntzer commented May 11, 2021

axisartist can generate "slanted" or "curved" axes defined using either
a custom Transform, or a custom pair of callables (forward, backward)
which define the Transform. Instead of repeatedly testing the two cases
in transform_xy and inv_transform_xy, just wrap the
pair-of-callables into a custom Transform subclass (which should
probably not be moved to the main library, as it uses the transposed
convention compared to the usual one), and expose it through a getter.

This allows later combining this transform using "standard" transform
addition (and get benefits such as single multiplication of matrices
in affine transforms, exact cancellation of inverses, or (later) more
accurate transforming of arcs in polar transforms), instead of having to
manually call successive transforms. See e.g. the two changes in the
local transform_xy definitions.

PR Summary

PR Checklist

  • Has pytest style unit tests (and pytest passes).
  • Is Flake 8 compliant (run flake8 on changed files to check).
  • New features are documented, with examples if plot related.
  • Documentation is sphinx and numpydoc compliant (the docs should build without error).
  • Conforms to Matplotlib style conventions (install flake8-docstrings and run flake8 --docstring-convention=all).
  • New features have an entry in doc/users/next_whats_new/ (follow instructions in README.rst there).
  • API changes documented in doc/api/next_api_changes/ (follow instructions in README.rst there).

axisartist can generate "slanted" or "curved" axes defined using either
a custom Transform, or a custom pair of callables (forward, backward)
which define the Transform.  Instead of repeatedly testing the two cases
in `transform_xy` and `inv_transform_xy`, just wrap the
pair-of-callables into a custom Transform subclass (which should
probably not be moved to the main library, as it uses the transposed
convention compared to the usual one), and expose it through a getter.

This allows later combining this transform using "standard" transform
addition (and get benefits such as single multiplication of matrices
in affine transforms, exact cancellation of inverses, or (later) more
accurate transforming of arcs in polar transforms), instead of having to
manually call successive transforms.  See e.g. the two changes in the
local transform_xy definitions.
Co-authored-by: Elliott Sales de Andrade <quantum.analyst@gmail.com>
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@jklymak jklymak left a comment

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Seems fine. I'd still rather this functionality was brought into core if we think it is useful.

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anntzer commented May 16, 2021

I agree, but I'm hoping that gap may be easier to bridge if we slowly nudge axisartist towards being "more standard" as well...

@QuLogic QuLogic added this to the v3.5.0 milestone May 17, 2021
@QuLogic QuLogic merged commit 9c9e0a0 into matplotlib:master May 17, 2021
@anntzer anntzer deleted the aat branch May 17, 2021 20:14
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3 participants