Figure: Deprecate the private _preprocess method (will be removed in v0.18.0)

[seisman]

The Figure._preprocess method was originally introduced in commit 4b414ce and later extended to wrap Figure._activate_figure in commit 5e69285.

The method was intended to take kwargs as input, modify them, and return the result. However, in practice, the input kwargs are never changed. As a result, Figure._preprocess serves only as a thin wrapper around Figure._activate_figure without adding any additional functionality.

This PR replaces all calls to Figure._preprocess with direct calls to Figure._activate_figure and deprecates the _preprocess method, which is scheduled for removal in four releases.

[Copilot]

Pull Request Overview

This PR deprecates the private _preprocess method by replacing its calls with direct invocations of _activate_figure, in preparation for removing _preprocess in v0.20.0. Key changes include updating all modules to remove the assignment from _preprocess, updating documentation in figure.py to warn users, and ensuring consistency across all call sites.

• Removed calls that captured kwargs from _preprocess in favor of a direct call to _activate_figure.
• Updated deprecation warnings and documentation in figure.py.
• Applied changes consistently across multiple modules (e.g., rose.py, psconvert.py, contour.py, etc.).

Reviewed Changes

Copilot reviewed 29 out of 29 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
pygmt/src/shift_origin.py	Replaced self._preprocess() with self._activate_figure().
pygmt/src/rose.py	Removed kwargs assignment from self._preprocess(**kwargs) and replaced it with self._activate_figure().
pygmt/src/psconvert.py	Updated call from self._preprocess(**kwargs) to self._activate_figure().
pygmt/src/plot3d.py	Removed kwargs processing via _preprocess and called _activate_figure() instead.
pygmt/src/plot.py	Replaced disappearing kwargs assignment with a bare _activate_figure() call.
pygmt/src/meca.py	Updated the method call to use _activate_figure() for figure activation.
pygmt/src/logo.py	Replaced _preprocess with _activate_figure() in logo initialization.
pygmt/src/legend.py	Updated to call _activate_figure() rather than reassigning kwargs.
pygmt/src/inset.py	Removed kwargs modification from _preprocess, calling _activate_figure() instead.
pygmt/src/image.py	Updated _preprocess call to _activate_figure() for image plotting.
pygmt/src/hlines.py	Changed _preprocess to _activate_figure() when plotting horizontal lines.
pygmt/src/histogram.py	Replaced assignment from _preprocess with a direct _activate_figure() call.
pygmt/src/grdview.py	Updated method call following the deprecation of _preprocess.
pygmt/src/grdimage.py	Removed kwargs reassignment from _preprocess in favor of _activate_figure().
pygmt/src/grdcontour.py	Replaced _preprocess with _activate_figure() for grdcontour plotting.
pygmt/src/contour.py	Updated call site to use _activate_figure() instead of capturing kwargs from _preprocess().
pygmt/src/colorbar.py	Removed return value dependency on _preprocess and directly activated the figure.
pygmt/src/coast.py	Replaced _preprocess call with _activate_figure() to streamline figure activation.
pygmt/src/basemap.py	Updated the call to use _activate_figure() instead of processing through _preprocess.
pygmt/figure.py	Added deprecation warning in _preprocess and guided users to use _activate_figure().

Comments suppressed due to low confidence (3)

pygmt/src/rose.py:201

• The call to _preprocess that reassigns kwargs has been replaced with a call to _activate_figure(), which no longer returns modified kwargs. Please confirm that downstream code does not rely on any modifications to kwargs returned from _preprocess.

kwargs = self._preprocess(**kwargs)

pygmt/src/psconvert.py:110

• Replacing the _preprocess call with _activate_figure() removes the reassignment of kwargs. Verify that no functionality is impacted by not capturing updated kwargs.

kwargs = self._preprocess(**kwargs)

pygmt/figure.py:130

• [nitpick] The deprecation warning in _preprocess is clear; consider reviewing the version numbers in both the comment and warning message for consistency to ensure future maintainability.

warnings.warn( ... )

[weiji14]

Technically this _preprocess method is private so we could just remove it 🔥 But if you think people are using it, we could do with 2 release cycles instead of 4.

[seisman]

Yes, people are using it. 2 release cycles sounds good to me.