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Title: Add legend support for PatchCollection by FazeelUsmani · Pull Request #30756 · matplotlib/matplotlib · GitHub

Open Graph Title: Add legend support for PatchCollection by FazeelUsmani · Pull Request #30756 · matplotlib/matplotlib

X Title: Add legend support for PatchCollection by FazeelUsmani · Pull Request #30756 · matplotlib/matplotlib

Description: PR summary Closes #23998 Why is this change necessary? PatchCollection instances do not currently display in legends even when assigned a label. This has been a long-standing limitation that forces users to create manual legend entries, making the API inconsistent with other collection types like PolyCollection and PathCollection. What problem does it solve? Before this fix, the following code would not display a legend entry: import matplotlib.pyplot as plt from matplotlib.collections import PatchCollection from matplotlib.patches import Polygon fig, ax = plt.subplots() p1 = Polygon([[0, 0], [100, 100], [200, 0]]) p2 = Polygon([[400, 0], [500, 100], [600, 0]]) pc = PatchCollection([p1, p2], label="my patches", facecolor='blue') ax.add_collection(pc) ax.legend() # Legend was empty ❌ plt.show() After this fix, the legend correctly displays the "my patches" label with a rectangular swatch matching the collection's visual properties. Implementation reasoning The implementation adds a new HandlerPatchCollection class that inherits from the existing HandlerPolyCollection. This approach: Eliminates code duplication: Both PatchCollection and PolyCollection inherit from Collection and share identical APIs for accessing colors, line styles, and other visual properties Maintains consistency: Uses the same legend representation (Rectangle) as PolyCollection Ensures maintainability: Bug fixes or enhancements to HandlerPolyCollection automatically benefit HandlerPatchCollection The handler extracts visual properties (face color, edge color, line width, line style) from the first patch in the collection and creates a rectangular legend entry. Minimum self-contained example import matplotlib.pyplot as plt import matplotlib.patches as mpatches from matplotlib.collections import PatchCollection fig, ax = plt.subplots() # Create various patches patches = [ mpatches.Circle((0.2, 0.5), 0.1), mpatches.Rectangle((0.5, 0.3), 0.2, 0.3), ] # Create PatchCollection with label pc = PatchCollection(patches, facecolor='red', edgecolor='black', linewidths=2, label='My patches') ax.add_collection(pc) ax.autoscale_view() # Legend now works! ax.legend() plt.show() PR checklist "closes #23998" is in the body of the PR description to link the related issue New and changed code is tested Added 5 comprehensive tests covering: Basic functionality Visual property preservation match_original=True parameter Empty collection edge case Visual regression test with @image_comparison [N/A] Plotting related features are demonstrated in an example This is a bug fix for existing functionality, not a new plotting feature Code examples are included in the What's New entry New Features and API Changes are noted with a directive and release note Added doc/release/next_whats_new/patchcollection_legend.rst Includes user-facing description and code example Documentation complies with general and docstring guidelines HandlerPatchCollection includes comprehensive docstring Follows matplotlib's docstring conventions Includes "See Also" section

Open Graph Description: PR summary Closes #23998 Why is this change necessary? PatchCollection instances do not currently display in legends even when assigned a label. This has been a long-standing limitation that forces...

X Description: PR summary Closes #23998 Why is this change necessary? PatchCollection instances do not currently display in legends even when assigned a label. This has been a long-standing limitation that forces...

Opengraph URL: https://github.com/matplotlib/matplotlib/pull/30756

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