add left and right title option (#2645)

src/metpy/plots/declarative.py

@@ -720,6 +720,20 @@ class MapPanel(Panel, ValidationMixin):
     This trait sets a user-defined title that will plot at the top center of the figure.
     """
 
+    left_title = Unicode(allow_none=True, default_value=None)
+    left_title.__doc__ = """A string to set a title for the figure with the location on the
+    top left of the figure.
+
+    This trait sets a user-defined title that will plot at the top left of the figure.
+    """
+
+    right_title = Unicode(allow_none=True, default_value=None)
+    right_title.__doc__ = """A string to set a title for the figure with the location on the
+    top right of the figure.
+
+    This trait sets a user-defined title that will plot at the top right of the figure.
+    """
+
     title_fontsize = Union([Int(), Float(), Unicode()], allow_none=True, default_value=None)
     title_fontsize.__doc__ = """An integer or string value for the font size of the title of
     the figure.
@@ -896,8 +910,18 @@ def draw(self):
                 self.ax.add_feature(feat, edgecolor=color, linewidth=width)
 
             # Use the set title or generate one.
-            title = self.title or ',\n'.join(plot.name for plot in self.plots)
-            self.ax.set_title(title, fontsize=self.title_fontsize)
+            if (self.right_title is None) and (self.left_title is None):
+                title = self.title or ',\n'.join(plot.name for plot in self.plots)
+                self.ax.set_title(title, fontsize=self.title_fontsize)
+            else:
+                if self.title is not None:
+                    self.ax.set_title(self.title, fontsize=self.title_fontsize)
+                if self.right_title is not None:
+                    self.ax.set_title(self.right_title, fontsize=self.title_fontsize,
+                                      loc='right')
+                if self.left_title is not None:
+                    self.ax.set_title(self.left_title, fontsize=self.title_fontsize,
+                                      loc='left')
             self._need_redraw = False
 
     def __copy__(self):

tests/plots/test_declarative.py

@@ -118,6 +118,37 @@ def test_declarative_contour():
     return pc.figure
 
 
+@pytest.mark.mpl_image_compare(remove_text=False, tolerance=0)
+@needs_cartopy
+def test_declarative_titles():
+    """Test making a contour plot with multiple titles."""
+    data = xr.open_dataset(get_test_data('narr_example.nc', as_file_obj=False))
+
+    contour = ContourPlot()
+    contour.data = data
+    contour.field = 'Temperature'
+    contour.level = 700 * units.hPa
+    contour.contours = 30
+    contour.linewidth = 1
+    contour.linecolor = 'red'
+
+    panel = MapPanel()
+    panel.area = 'us'
+    panel.projection = 'lcc'
+    panel.layers = ['coastline']
+    panel.left_title = '700-hPa Temperature'
+    panel.right_title = 'Valid at a time'
+    panel.title = 'Plot of data'
+    panel.plots = [contour]
+
+    pc = PanelContainer()
+    pc.size = (8.0, 8)
+    pc.panels = [panel]
+    pc.draw()
+
+    return pc.figure
+
+
 @pytest.mark.mpl_image_compare(remove_text=True, tolerance=0.01)
 @needs_cartopy
 def test_declarative_smooth_contour():