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1. iccir

   added

   topic: path handling

   on Sep 10, 2026
2. ayshih commented on Sep 10, 2026

   

   ayshih

   on Sep 10, 2026

   Last edited by ayshih

   Contributor

   More actions

   Here is an interactive example that shows how the existing contains() code sometimes matches one fill rule and not the other, depending on the path used for the PathPatch.

   import numpy as np
   
   import matplotlib.pyplot as plt
   from matplotlib.patches import PathPatch
   from matplotlib.path import Path
   
   twisted_vertices = np.array([[0, 0, 6, 6, 1, 1, 5, 5, 2, 2, 4, 4, 3, 3, 5, 5, 0],
                                [2, 5, 5, 0, 0, 7, 7, 3, 3, 4, 4, 6, 6, 1, 1, 2, 2]]).T
   twisted_codes = [Path.MOVETO] + [Path.LINETO] * (len(twisted_vertices) - 1)
   
   square_vertices = np.array([[-1, -1], [-1, 1], [1, 1], [1, -1], [-1, -1]])
   square_codes = [Path.MOVETO, Path.LINETO, Path.LINETO, Path.LINETO, Path.LINETO]
   
   fig, axs = plt.subplots(2, 3, figsize=(7, 4), layout='constrained')
   
   for i, fill_rule in enumerate(['nonzero', 'evenodd']):
       axs[i, 0].text(-1.2, 0, f'fill_rule={fill_rule}', rotation='vertical', va='center')
   
       donut1 = Path(np.vstack([square_vertices, square_vertices / 2]), square_codes * 2)
       axs[i, 0].add_patch(PathPatch(donut1, fc='g', ec='m', fill_rule=fill_rule))
   
       twisted = Path(twisted_vertices, twisted_codes)
       axs[i, 1].add_patch(PathPatch(twisted, fc='g', ec='m', fill_rule=fill_rule))
   
       donut2 = Path(np.vstack([square_vertices, square_vertices[::-1, :] / 2]), square_codes * 2)
       axs[i, 2].add_patch(PathPatch(donut2, fc='g', ec='m', fill_rule=fill_rule))
   
       for j in range(axs.shape[1]):
           axs[i, j].autoscale_view()
           axs[i, j].set_axis_off()
   
   axs[0, 0].set_title('contains() == nonzero')
   axs[0, 1].set_title('contains() == even-odd')
   axs[0, 2].set_title('contains() != either')
   
   def on_mouse_move(event):
       if event.inaxes is None:
           return
   
       for ax in axs.flatten():
           patch = ax.patches[0]
           patch.set_facecolor('r' if patch.contains(event)[0] else 'g')
   
       fig.canvas.draw_idle()
   
   fig.canvas.mpl_connect('motion_notify_event', on_mouse_move)
   
   plt.show()
3. ayshih commented on Sep 10, 2026

   

   ayshih

   on Sep 10, 2026

   Contributor

   More actions

   I've already verified how to modify point_in_path_impl() in _path.h to be fully consistent with one fill rule or the other. The thought needed is how to set up the (internal) API to carry the current fill rule down to that level to switch which one is being calculated.

   👍React with 👍1Reacted by Greg Lucas