add declarative layer attributes control

src/metpy/plots/declarative.py

@@ -697,6 +697,22 @@ class MapPanel(Panel, ValidationMixin):
     Cartopy Feature objects.
     """
 
+    layers_edgecolor = List(Unicode(allow_none=True), default_value=['black'])
+    layers_edgecolor.__doc__ = """A list of strings for a pre-defined edgecolor for a layer.
+
+    An option to set a different color for the map layer edge colors. Length of list should
+    match that of layers if not using default value. Behavior is to repeat colors if not enough
+    provided by user. Use `None` value for 'ocean', 'lakes', 'rivers', and 'land'.
+    """
+
+    layers_linewidth = List(Union([Int(), Float()], allow_none=True), default_value=[1])
+    layers_linewidth.__doc__ = """A list of values defining the linewidth for a layer.
+
+    An option to set a different color for the map layer edge colors. Length of list should
+    match that of layers if not using default value. Behavior is to repeat colors if not enough
+    provided by user. Use `None` value for 'ocean', 'lakes', 'rivers', and 'land'.
+    """
+
     title = Unicode()
     title.__doc__ = """A string to set a title for the figure.
 
@@ -866,8 +882,17 @@ def draw(self):
                     p.draw()
 
             # Add all of the maps
-            for feat in self._layer_features:
-                self.ax.add_feature(feat)
+            if len(self.layers) > len(self.layers_edgecolor):
+                self.layers_edgecolor *= len(self.layers)
+            if len(self.layers) > len(self.layers_linewidth):
+                self.layers_linewidth *= len(self.layers)
+            for i, feat in enumerate(self._layer_features):
+                if self.layers[i] in ['', 'land', 'lake', 'river']:
+                    color = 'face'
+                else:
+                    color = self.layers_edgecolor[i]
+                width = self.layers_linewidth[i]
+                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)

tests/plots/test_declarative.py

@@ -288,6 +288,36 @@ def test_declarative_contour_options():
     return pc.figure
 
 
+@pytest.mark.mpl_image_compare(remove_text=True, tolerance=0.08)
+@needs_cartopy
+def test_declarative_layers_plot_options():
+    """Test making a contour plot."""
+    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 = 5
+    contour.linewidth = 1
+    contour.linecolor = 'grey'
+
+    panel = MapPanel()
+    panel.area = 'us'
+    panel.projection = 'lcc'
+    panel.layers = ['coastline', 'usstates', 'borders']
+    panel.layers_edgecolor = ['blue', 'red', 'black']
+    panel.layers_linewidth = [0.75, 0.75, 1]
+    panel.plots = [contour]
+
+    pc = PanelContainer()
+    pc.size = (8, 8)
+    pc.panels = [panel]
+    pc.draw()
+
+    return pc.figure
+
+
 @pytest.mark.mpl_image_compare(remove_text=True, tolerance=0.0188)
 @needs_cartopy
 def test_declarative_contour_convert_units():