Merge pull request #17521 from Struan-Murray/e17518

Remove font warning when legend is added while using Tex

lib/matplotlib/offsetbox.py

@@ -882,7 +882,8 @@ def get_window_extent(self, renderer):
 
     def get_extent(self, renderer):
         _, h_, d_ = renderer.get_text_width_height_descent(
-            "lp", self._text._fontproperties, ismath=False)
+            "lp", self._text._fontproperties,
+            ismath="TeX" if self._text.get_usetex() else False)
 
         bbox, info, yd = self._text._get_layout(renderer)
         w, h = bbox.width, bbox.height

lib/matplotlib/tests/test_legend.py

@@ -637,6 +637,22 @@ def test_alpha_handles():
     assert lh.get_edgecolor()[:-1] == hh[1].get_edgecolor()[:-1]
 
 
+@pytest.mark.skipif(
+    not mpl.checkdep_usetex(True),
+    reason="This test needs a TeX installation")
+def test_usetex_no_warn(caplog):
+    mpl.rcParams['font.family'] = 'serif'
+    mpl.rcParams['font.serif'] = 'Computer Modern'
+    mpl.rcParams['text.usetex'] = True
+
+    fig, ax = plt.subplots()
+    ax.plot(0, 0, label='input')
+    ax.legend(title="My legend")
+
+    fig.canvas.draw()
+    assert "Font family ['serif'] not found." not in caplog.text
+
+
 def test_warn_big_data_best_loc():
     fig, ax = plt.subplots()
     fig.canvas.draw()  # So that we can call draw_artist later.