matplotlib · jklymak · Nov 5, 2020 · Feb 23, 2021 · Apr 23, 2021 · dstansby
diff --git a/doc/api/next_api_changes/behavior/18900-JMK.rst b/doc/api/next_api_changes/behavior/18900-JMK.rst
@@ -0,0 +1,26 @@
+Axes used to make colorbar now wrapped
+======================================
+
+The axes used to place a colorbar is now wrapped by a new parent class
+(``ColorbarAxes``) when the colorbar is created::
+
+    cb = fig.colorbar(im, cax=cax)
+
+Now ``cb.ax`` returns the parent ``ColorbarAxes``, and to get
+``cax`` back, you can do::
+
+    cb.ax.parent_axes
+
+The parent axes (``cb.ax.parent_axes``) handles the
+placement of the colorbar axes object, and its aspect ratio, but the child
+axes (``cb.ax``)  handles all the tick parameters, labelling, and holds the
+artists that make up the colorbar.  We have attempted to dispatch the
+appropriate colorbar methods to the appropriate axes.  
+
+Colorbar lines no longer clipped
+================================
+
+If a colorbar has lines added to it (e.g. for contour lines), these will
+no longer be clipped.  This is an improvement for lines on the edge of
+the colorbar, but could lead to lines off the colorbar if the limits of
+the colorbar are changed.
diff --git a/lib/matplotlib/_constrained_layout.py b/lib/matplotlib/_constrained_layout.py
@@ -451,13 +451,15 @@ def _get_pos_and_bbox(ax, renderer):
     pos = pos.transformed(fig.transSubfigure - fig.transFigure)
     try:
         tightbbox = ax.get_tightbbox(renderer=renderer, for_layout_only=True)
+        print('tight', tightbbox)
     except TypeError:
         tightbbox = ax.get_tightbbox(renderer=renderer)
 
     if tightbbox is None:
         bbox = pos
     else:
         bbox = tightbbox.transformed(fig.transFigure.inverted())
+    print('bbox', bbox)
     return pos, bbox