Merge pull request #10715 from jklymak/enh-rc-legend-title-fontsize

anntzer · web-flow · commit dd5f241a57a6 · 2018-05-04T14:32:27.000-07:00
ENH: add title_fontsize to legend
diff --git a/doc/users/next_whats_new/legend_title_fontsize_kwarg.rst b/doc/users/next_whats_new/legend_title_fontsize_kwarg.rst
@@ -0,0 +1,8 @@
+Legend now has a title_fontsize kwarg
+-------------------------------------
+
+The title for a `.Figure.legend` and `.Axes.legend` can now have its
+fontsize set via the ``title_fontsize`` kwarg, defaults to ``None``, which
+means the legend title will have the same fontsize as the axes default
+fontsize (*not* the legend fontsize, set by the ``fontsize`` kwarg or
+:rc:`legend.fontsize`).
diff --git a/lib/matplotlib/legend.py b/lib/matplotlib/legend.py
@@ -232,6 +232,9 @@ def _update_bbox_to_anchor(self, loc_in_canvas):
 title : str or None
     The legend's title. Default is no title (``None``).
 
+title_fontsize: str or None
+    The fontsize of the legend's title.  Default is the default fontsize.
+
 borderpad : float or None
     The fractional whitespace inside the legend border.
     Measured in font-size units.
@@ -333,7 +336,7 @@ def __init__(self, parent, handles, labels,
                                  # box, none use rc
                  shadow=None,
                  title=None,  # set a title for the legend
-
+                 title_fontsize=None,  # set to ax.fontsize if None
                  framealpha=None,  # set frame alpha
                  edgecolor=None,  # frame patch edgecolor
                  facecolor=None,  # frame patch facecolor
@@ -539,7 +542,12 @@ def __init__(self, parent, handles, labels,
             self.get_frame().set_alpha(framealpha)
 
         self._loc = loc
-        self.set_title(title)
+        # figure out title fontsize:
+        if title_fontsize is not None:
+            tprop = FontProperties(size=title_fontsize)
+        else:
+            tprop = None
+        self.set_title(title, prop=tprop)
         self._last_fontsize_points = self._fontsize
         self._draggable = None
 
diff --git a/lib/matplotlib/tests/test_legend.py b/lib/matplotlib/tests/test_legend.py
@@ -502,3 +502,11 @@ def test_legend_proper_window_extent():
     leg = ax.legend()
     x02 = leg.get_window_extent(fig.canvas.get_renderer()).x0
     assert pytest.approx(x01*2, 0.1) == x02
+
+
+def test_legend_title_fontsize():
+    # test the title_fontsize kwarg
+    fig, ax = plt.subplots()
+    ax.plot(range(10))
+    leg = ax.legend(title='Aardvark', title_fontsize=22)
+    assert leg.get_title().get_fontsize() == 22
