Merge pull request matplotlib#25247 from anntzer/ca

Turn ContourSet into a standard Collection artist.

Author: tacaswell

Diff for: doc/api/next_api_changes/deprecations/25247-AL.rst

@@ -0,0 +1,9 @@
+``ContourSet.collections``
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+... is deprecated.  `.ContourSet` is now implemented as a single `.Collection` of paths,
+each path corresponding to a contour level, possibly including multiple unconnected
+components.
+
+During the deprecation period, accessing ``ContourSet.collections`` will revert the
+current ContourSet instance to the old object layout, with a separate `.PathCollection`
+per contour level.

Diff for: galleries/examples/images_contours_and_fields/contour_demo.py

@@ -85,7 +85,9 @@
                 linewidths=2, extent=(-3, 3, -2, 2))
 
 # Thicken the zero contour.
-CS.collections[6].set_linewidth(4)
+lws = np.resize(CS.get_linewidth(), len(levels))
+lws[6] = 4
+CS.set_linewidth(lws)
 
 ax.clabel(CS, levels[1::2],  # label every second level
           inline=True, fmt='%1.1f', fontsize=14)

Diff for: galleries/examples/images_contours_and_fields/contour_image.py

@@ -56,9 +56,7 @@
 
 # We don't really need dashed contour lines to indicate negative
 # regions, so let's turn them off.
-
-for c in cset2.collections:
-    c.set_linestyle('solid')
+cset2.set_linestyle('solid')
 
 # It is easier here to make a separate call to contour than
 # to set up an array of colors and linewidths.

Diff for: galleries/examples/images_contours_and_fields/contours_in_optimization_demo.py

@@ -17,7 +17,6 @@
 `~matplotlib.patheffects.TickedStroke` to illustrate a constraint in
 a typical optimization problem, the angle should be set between
 zero and 180 degrees.
-
 """
 
 import matplotlib.pyplot as plt
@@ -48,16 +47,13 @@
 ax.clabel(cntr, fmt="%2.1f", use_clabeltext=True)
 
 cg1 = ax.contour(x1, x2, g1, [0], colors='sandybrown')
-plt.setp(cg1.collections,
-         path_effects=[patheffects.withTickedStroke(angle=135)])
+cg1.set(path_effects=[patheffects.withTickedStroke(angle=135)])
 
 cg2 = ax.contour(x1, x2, g2, [0], colors='orangered')
-plt.setp(cg2.collections,
-         path_effects=[patheffects.withTickedStroke(angle=60, length=2)])
+cg2.set(path_effects=[patheffects.withTickedStroke(angle=60, length=2)])
 
 cg3 = ax.contour(x1, x2, g3, [0], colors='mediumblue')
-plt.setp(cg3.collections,
-         path_effects=[patheffects.withTickedStroke(spacing=7)])
+cg3.set(path_effects=[patheffects.withTickedStroke(spacing=7)])
 
 ax.set_xlim(0, 4)
 ax.set_ylim(0, 4)

Diff for: galleries/examples/misc/patheffect_demo.py

@@ -29,8 +29,7 @@
 ax2.imshow(arr)
 cntr = ax2.contour(arr, colors="k")
 
-plt.setp(cntr.collections, path_effects=[
-    patheffects.withStroke(linewidth=3, foreground="w")])
+cntr.set(path_effects=[patheffects.withStroke(linewidth=3, foreground="w")])
 
 clbls = ax2.clabel(cntr, fmt="%2.0f", use_clabeltext=True)
 plt.setp(clbls, path_effects=[

Diff for: galleries/examples/misc/tickedstroke_demo.py

@@ -88,16 +88,13 @@
 ax.clabel(cntr, fmt="%2.1f", use_clabeltext=True)
 
 cg1 = ax.contour(x1, x2, g1, [0], colors='sandybrown')
-plt.setp(cg1.collections,
-         path_effects=[patheffects.withTickedStroke(angle=135)])
+cg1.set(path_effects=[patheffects.withTickedStroke(angle=135)])
 
 cg2 = ax.contour(x1, x2, g2, [0], colors='orangered')
-plt.setp(cg2.collections,
-         path_effects=[patheffects.withTickedStroke(angle=60, length=2)])
+cg2.set(path_effects=[patheffects.withTickedStroke(angle=60, length=2)])
 
 cg3 = ax.contour(x1, x2, g3, [0], colors='mediumblue')
-plt.setp(cg3.collections,
-         path_effects=[patheffects.withTickedStroke(spacing=7)])
+cg3.set(path_effects=[patheffects.withTickedStroke(spacing=7)])
 
 ax.set_xlim(0, 4)
 ax.set_ylim(0, 4)

Diff for: lib/matplotlib/axes/_base.py

@@ -2171,15 +2171,9 @@ def _sci(self, im):
         ``pyplot.viridis``, and other functions such as `~.pyplot.clim`.  The
         current image is an attribute of the current Axes.
         """
-        _api.check_isinstance(
-            (mpl.contour.ContourSet, mcoll.Collection, mimage.AxesImage),
-            im=im)
-        if isinstance(im, mpl.contour.ContourSet):
-            if im.collections[0] not in self._children:
-                raise ValueError("ContourSet must be in current Axes")
-        elif im not in self._children:
-            raise ValueError("Argument must be an image, collection, or "
-                             "ContourSet in this Axes")
+        _api.check_isinstance((mcoll.Collection, mimage.AxesImage), im=im)
+        if im not in self._children:
+            raise ValueError("Argument must be an image or collection in this Axes")
         self._current_image = im
 
     def _gci(self):

Diff for: lib/matplotlib/colorbar.py

@@ -750,15 +750,15 @@ def add_lines(self, *args, **kwargs):
              lambda self, levels, colors, linewidths, erase=True: locals()],
             self, *args, **kwargs)
         if "CS" in params:
-            self, CS, erase = params.values()
-            if not isinstance(CS, contour.ContourSet) or CS.filled:
+            self, cs, erase = params.values()
+            if not isinstance(cs, contour.ContourSet) or cs.filled:
                 raise ValueError("If a single artist is passed to add_lines, "
                                  "it must be a ContourSet of lines")
             # TODO: Make colorbar lines auto-follow changes in contour lines.
             return self.add_lines(
-                CS.levels,
-                CS.to_rgba(CS.cvalues, CS.alpha),
-                [coll.get_linewidths()[0] for coll in CS.collections],
+                cs.levels,
+                cs.to_rgba(cs.cvalues, cs.alpha),
+                cs.get_linewidths(),
                 erase=erase)
         else:
             self, levels, colors, linewidths, erase = params.values()