Refactor axis sharing logic and improve test coverage for UltraPlot

[cvanelteren]

Closes #348

This PR refactors axis sharing logic and adds comprehensive tests to improve coverage and robustness across UltraPlot’s core plotting modules.

Key Changes

Core Logic

• Refactored axis sharing checks in GeoAxes and Figure:

  • Replaced usage of _get_sharing_level() with direct checks on _sharex and _sharey for clarity and correctness.
  • Updated axis sharing logic to use the correct sharing level for each axis (x or y), ensuring more precise control over label and tick sharing.
  • Improved handling of axis sharing for geographic axes, passing the which argument to clarify axis context.

• Removed unused method: _get_sharing_level() from Figure.

Tests

• Added new tests in test_figure.py:

  • Coverage for _get_renderer to ensure renderer acquisition works as expected.
  • Coverage for _share_labels_with_others, including both early return (no sharing) and execution with sharing enabled.

• Added new tests in test_sharing.py:

  • Parametrized tests for x and y axis sharing levels, verifying correct label and tick visibility for all sharing modes and Matplotlib versions.
  • Ensures border axes are correctly detected and labels/ticks are only visible where appropriate.

• Improved tests in test_geographic.py:

  • Parametrized sharing level tests for geographic axes, ensuring correct sharing of limits and labels.

Why?

• Improved clarity and maintainability: Directly checking _sharex and _sharey makes the code easier to understand and less error-prone.
• Better test coverage: Addresses previously uncovered lines and branches, as highlighted by Codecov.
• More robust axis sharing: Ensures correct behavior for all sharing levels, including edge cases and version differences in Matplotlib.

[codecov]

Codecov Report

❌ Patch coverage is 92.37473% with 35 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
ultraplot/figure.py	88.02%	14 Missing and 9 partials ⚠️
ultraplot/tests/test_sharing.py	92.98%	2 Missing and 2 partials ⚠️
ultraplot/gridspec.py	40.00%	2 Missing and 1 partial ⚠️
ultraplot/utils.py	92.85%	2 Missing and 1 partial ⚠️
ultraplot/axes/polar.py	85.71%	1 Missing ⚠️
ultraplot/tests/test_subplots.py	98.71%	0 Missing and 1 partial ⚠️

📢 Thoughts on this report? Let us know!

[Copilot]

Pull Request Overview

This PR refactors axis sharing logic in UltraPlot by replacing a centralized sharing level method with direct checks on sharing attributes, and adds comprehensive test coverage for axis sharing behavior across different modules.

• Removes the _get_sharing_level() method and replaces its usage with direct checks on _sharex and _sharey attributes
• Adds parametrized tests for axis sharing levels in both regular and geographic plotting contexts
• Improves test coverage for renderer acquisition and label sharing methods

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
ultraplot/tests/test_sharing.py	New comprehensive test file covering x/y axis sharing levels with parametrized tests
ultraplot/tests/test_geographic.py	Converts sharing level test to parametrized format and updates sharing logic reference
ultraplot/tests/test_figure.py	Adds tests for renderer acquisition and label sharing methods
ultraplot/figure.py	Removes _get_sharing_level() method and updates sharing checks to use direct attribute access
ultraplot/axes/geo.py	Updates axis sharing logic to use direct sharing level checks and adds which parameter

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[cvanelteren]

Some tests fail due to image mismatch but visually look ok; sometimes there is a title that is slightly shifted. The test test_geo_with_panels now fails because I copied the formatters. Panels for geo now copy the formatters for the relevant range (y or x) so that plotting is within the same data range. Formatters are updated too when relevant. This effectively creates some crowding on the x-values in test_geo_with_panels

[beckermr]

This PR is pretty hefty and so will take time for me to review. Thanks for the hard work!

[cvanelteren]

Thanks. Thinking of breaking it up to make it more manageable. Will see if I can do that to ensure tractability.

[cvanelteren]

Will do a diff tomorrow!

[cvanelteren]

I split this PR into two, see #372 and #373. The should be handled in sequential order @beckermr