class labels_bbox_style variable have now default style value that ne…

…eds to be overwritten

lib/cartopy/mpl/gridliner.py

@@ -271,6 +271,9 @@ def __init__(self, axes, crs, draw_labels=False, xlocator=None,
         #: for styling of the text labels.
         self.ylabel_style = {}
 
+        # bbox style for grid labels
+        self.labels_bbox_style = {'pad': 0, 'visible': False}
+
         #: The padding from the map edge to the x labels in points.
         self.xpadding = 5
 
@@ -600,10 +603,11 @@ def _draw_gridliner(self, nx=None, ny=None, renderer=None):
                         for i, (pt0, pt1) in enumerate([tail, head]):
                             kw, angle, loc = self._segment_to_text_specs(
                                 pt0, pt1, lonlat)
-                            if not getattr(self, loc+'_labels'):
+                            if not getattr(self, loc + '_labels'):
                                 continue
+
                             kw.update(label_style,
-                                      bbox={'pad': 0, 'visible': False})
+                                      bbox=self.labels_bbox_style)
                             text = formatter(tick_value)
 
                             if self.y_inline and lonlat == 'lat':
@@ -646,7 +650,7 @@ def _segment_to_text_specs(self, pt0, pt1, lonlat):
         """Get appropriate kwargs for a label from lon or lat line segment"""
         x0, y0 = pt0
         x1, y1 = pt1
-        angle = np.arctan2(y0-y1, x0-x1) * 180 / np.pi
+        angle = np.arctan2(y0 - y1, x0 - x1) * 180 / np.pi
         kw, loc = self._segment_angle_to_text_specs(angle, lonlat)
         return kw, angle, loc
 
@@ -679,11 +683,11 @@ def _text_angle_to_specs_(self, angle, lonlat):
 
         elif angle > 45:
             loc = 'top'
-            kw.update(ha='center', va='bottom', rotation=angle-90)
+            kw.update(ha='center', va='bottom', rotation=angle - 90)
 
         else:
             loc = 'bottom'
-            kw.update(ha='center', va='top', rotation=angle+90)
+            kw.update(ha='center', va='top', rotation=angle + 90)
 
         return kw, loc
 
@@ -760,7 +764,7 @@ def remove_path_dupes(path):
                           'va': artist.get_va()}
             # Compute angles to try
             angles = [None]
-            for abs_delta_angle in np.arange(delta_angle, max_delta_angle+1,
+            for abs_delta_angle in np.arange(delta_angle, max_delta_angle + 1,
                                              delta_angle):
                 angles.append(artist._angle + abs_delta_angle)
                 angles.append(artist._angle - abs_delta_angle)

lib/cartopy/tests/mpl/test_gridliner.py

@@ -16,10 +16,8 @@
     LATITUDE_FORMATTER, LONGITUDE_FORMATTER,
     classic_locator, classic_formatter)
 
-
 from cartopy.tests.mpl import MPL_VERSION, ImageTesting
 
-
 TEST_PROJS = [
     ccrs.PlateCarree,
     ccrs.AlbersEqualArea,
@@ -216,7 +214,6 @@ def test_grid_labels():
               tolerance=grid_label_tol if ccrs.PROJ4_VERSION < (7, 1, 0)
               else 4)
 def test_grid_labels_tight():
-
     # Ensure tight layout accounts for gridlines
     fig = plt.figure(figsize=(7, 5))
 
@@ -307,9 +304,35 @@ def test_grid_labels_inline_usa():
         else:
             ax.gridlines(draw_labels=True, auto_inline=True, clip_on=True)
         ax.coastlines(resolution="110m")
+
     plt.subplots_adjust(wspace=0.35, hspace=0.35)
 
 
+@ImageTesting(["gridliner_labels_bbox_style"], tolerance=grid_label_tol)
+def test_gridliner_labels_bbox_style():
+    top = 49.3457868  # north lat
+    left = -124.7844079  # west long
+    right = -66.9513812  # east long
+    bottom = 24.7433195  # south lat
+
+    plt.figure(figsize=(6, 3))
+    ax = plt.subplot(1, 1, 1, projection=ccrs.PlateCarree())
+    ax.coastlines(resolution="110m")
+    ax.set_extent([left, right, bottom, top],
+                  crs=ccrs.PlateCarree())
+    gl = ax.gridlines(draw_labels=True)
+
+    bbox_style = {
+        "pad": 0,
+        "visible": True,
+        "facecolor": "white",
+        "edgecolor": "black",
+        "boxstyle": "round, pad=0.2",
+    }
+
+    gl.labels_bbox_style = bbox_style
+
+
 @pytest.mark.parametrize(
     "proj,gcrs,xloc,xfmt,xloc_expected,xfmt_expected",
     [