Adding a temporary pcolormesh snapping rcParam to remove the need to update many baseline images.

greglucas · greglucas · commit 4409dad8b5ab · 2020-07-04T08:16:40.000-06:00
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -6087,6 +6087,8 @@ def pcolormesh(self, *args, alpha=None, norm=None, cmap=None, vmin=None,
         collection = mcoll.QuadMesh(Nx - 1, Ny - 1, coords,
                                     antialiased=antialiased, shading=shading,
                                     **kwargs)
+        snap = kwargs.get('snap', rcParams['pcolormesh.snap'])
+        collection.set_snap(snap)
         collection.set_alpha(alpha)
         collection.set_array(C)
         collection.set_cmap(cmap)
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -1090,6 +1090,7 @@ def _convert_validator_spec(key, conv):
 
     ## pcolor(mesh) props:
     "pcolor.shading": ["auto", "flat", "nearest", "gouraud"],
+    "pcolormesh.snap": validate_bool,
 
     ## patch props
     "patch.linewidth":       validate_float,  # line width in points
diff --git a/matplotlibrc.template b/matplotlibrc.template
@@ -131,6 +131,9 @@
 #markers.fillstyle: full  # {full, left, right, bottom, top, none}
 
 #pcolor.shading : flat
+#pcolormesh.snap : True  # Whether to snap the mesh to pixel boundaries. This
+                         # is provided solely to allow old test images to remain
+                         # unchanged. Set to False to obtain the previous behavior.
 
 ## ***************************************************************************
 ## * PATCHES                                                                 *
