Merge Colorbar and ColorbarBase.

ColorbarBase differs from Colorbar in that it is not associated with a
ScalarMappable (but constructed from explicit cmap/norm), but we already
document in Figure.colorbar that the preferred way to draw colorbars not
associated with an existing artist is to create an empty ScalarMappable
to provide `norm` and `cmap`.

Hence, likewise merge Colorbar and ColorbarBase (creating the
ScalarMappable on-the-fly if no mappable is passed to the constructor),
which should make the APIs clearer.  (Note that we are already
discouraging users to directly call either class' constructors,
anyways).  We could deprecate the backcompat APIs (i.e., the
`ColorbarBase` alias, the `cmap` and `norm` kwargs, and the different
semantics of `add_lines`), but that can be done later; this PR should be
entirely backcompatible.

doc/users/prev_whats_new/whats_new_3.0.rst

@@ -60,11 +60,11 @@ frame. Padding and separation parameters can be adjusted.
 Add ``minorticks_on()/off()`` methods for colorbar
 --------------------------------------------------
 
-A new method `~.colorbar.ColorbarBase.minorticks_on` has been added to
+A new method ``ColorbarBase.minorticks_on`` has been added to
 correctly display minor ticks on a colorbar. This method doesn't allow the
 minor ticks to extend into the regions beyond vmin and vmax when the *extend*
 keyword argument (used while creating the colorbar) is set to 'both', 'max' or
-'min'. A complementary method `~.colorbar.ColorbarBase.minorticks_off` has
+'min'. A complementary method ``ColorbarBase.minorticks_off`` has
 also been added to remove the minor ticks on the colorbar.
 
 

doc/users/prev_whats_new/whats_new_3.3.0.rst

@@ -285,7 +285,7 @@ Align labels to Axes edges
 --------------------------
 
 `~.axes.Axes.set_xlabel`, `~.axes.Axes.set_ylabel` and
-`.ColorbarBase.set_label` support a parameter ``loc`` for simplified
+``ColorbarBase.set_label`` support a parameter ``loc`` for simplified
 positioning. For the xlabel, the supported values are 'left', 'center', or
 'right'. For the ylabel, the supported values are 'bottom', 'center', or
 'top'.

examples/color/colorbar_basics.py

@@ -54,5 +54,5 @@
 #
 #    - `matplotlib.axes.Axes.imshow` / `matplotlib.pyplot.imshow`
 #    - `matplotlib.figure.Figure.colorbar` / `matplotlib.pyplot.colorbar`
-#    - `matplotlib.colorbar.ColorbarBase.minorticks_on`
-#    - `matplotlib.colorbar.ColorbarBase.minorticks_off`
+#    - `matplotlib.colorbar.Colorbar.minorticks_on`
+#    - `matplotlib.colorbar.Colorbar.minorticks_off`

examples/images_contours_and_fields/image_masked.py

@@ -79,4 +79,4 @@
 #    - `matplotlib.axes.Axes.imshow` / `matplotlib.pyplot.imshow`
 #    - `matplotlib.figure.Figure.colorbar` / `matplotlib.pyplot.colorbar`
 #    - `matplotlib.colors.BoundaryNorm`
-#    - `matplotlib.colorbar.ColorbarBase.set_label`
+#    - `matplotlib.colorbar.Colorbar.set_label`