Include gridliner labels in tight bbox calculation

lib/cartopy/mpl/geoaxes.py

@@ -430,19 +430,13 @@ def hold_limits(self, hold=True):
                 (self.ignore_existing_data_limits,
                     self._autoscaleXon, self._autoscaleYon) = other
 
-    @matplotlib.artist.allow_rasterization
-    def draw(self, renderer=None, **kwargs):
+    def _draw_preprocess(self, renderer):
         """
-        Extend the standard behaviour of :func:`matplotlib.axes.Axes.draw`.
-
-        Draw grid lines and image factory results before invoking standard
-        Matplotlib drawing. A global range is used if no limits have yet
-        been set.
-
+        Perform pre-processing steps shared between :func:`GeoAxes.draw`
+        and :func:`GeoAxes.get_tightbbox`.
         """
         # If data has been added (i.e. autoscale hasn't been turned off)
         # then we should autoscale the view.
-
         if self.get_autoscale_on() and self.ignore_existing_data_limits:
             self.autoscale_view()
 
@@ -454,6 +448,32 @@ def draw(self, renderer=None, **kwargs):
         for gl in self._gridliners:
             gl._draw_gridliner(renderer=renderer)
 
+    def get_tightbbox(self, renderer, *args, **kwargs):
+        """
+        Extend the standard behaviour of
+        :func:`matplotlib.axes.Axes.get_tightbbox`.
+
+        Adjust the axes aspect ratio, background patch location, and add
+        gridliners before calculating the tight bounding box.
+        """
+        # Shared processing steps
+        self._draw_preprocess(renderer)
+
+        return matplotlib.axes.Axes.get_tightbbox(
+            self, renderer, *args, **kwargs)
+
+    @matplotlib.artist.allow_rasterization
+    def draw(self, renderer=None, **kwargs):
+        """
+        Extend the standard behaviour of :func:`matplotlib.axes.Axes.draw`.
+
+        Draw grid lines and image factory results before invoking standard
+        Matplotlib drawing. A global range is used if no limits have yet
+        been set.
+        """
+        # Shared processing steps
+        self._draw_preprocess(renderer)
+
         # XXX This interface needs a tidy up:
         #       image drawing on pan/zoom;
         #       caching the resulting image;

lib/cartopy/tests/mpl/test_gridliner.py

@@ -143,6 +143,8 @@ def test_gridliner_specified_lines():
         grid_label_inline_tol = 6.4
         grid_label_inline_usa_tol = 4.0
 else:
+    # Skip test_grid_labels_tight for matplotlib 1.5.1 because it
+    # is not possible to override tight bounding box calculation
     grid_label_image = 'gridliner_labels_1.5'
     grid_label_tol = 1.8
     grid_label_inline_image = 'gridliner_labels_inline_1.5'
@@ -234,6 +236,50 @@ def test_grid_labels():
     plt.subplots_adjust(wspace=0.25, hspace=0.25)
 
 
+@pytest.mark.skipif(
+    MPL_VERSION < '2.0.0',
+    reason='Impossible to override tight layout algorithm in matplotlib < 2.0.0')
+@pytest.mark.natural_earth
+@ImageTesting(['gridliner_labels_tight'], tolerance=grid_label_tol)
+def test_grid_labels_tight():
+
+    # Ensure tight layout accounts for gridlines
+    fig = plt.figure(figsize=(7, 5))
+
+    crs_pc = ccrs.PlateCarree()
+    crs_merc = ccrs.Mercator()
+
+    ax = fig.add_subplot(2, 2, 1, projection=crs_pc)
+    ax.coastlines(resolution="110m")
+    ax.gridlines(draw_labels=True)
+
+    ax = fig.add_subplot(2, 2, 2, projection=crs_merc)
+    ax.coastlines(resolution="110m")
+    ax.gridlines(draw_labels=True)
+
+    # Matplotlib tight layout is also incorrect if cartopy fails
+    # to adjust aspect ratios first. Relevant when aspect ratio has
+    # changed due to set_extent.
+    ax = fig.add_subplot(2, 2, 3, projection=crs_pc)
+    ax.set_extent([-20, 10.0, 45.0, 70.0])
+    ax.coastlines(resolution="110m")
+    ax.gridlines(draw_labels=True)
+
+    ax = fig.add_subplot(2, 2, 4, projection=crs_merc)
+    ax.set_extent([-20, 10.0, 45.0, 70.0], crs=crs_pc)
+    ax.coastlines(resolution="110m")
+    gl = ax.gridlines(draw_labels=True)
+    gl.rotate_labels = False
+
+    # Apply tight layout
+    fig.tight_layout()
+
+    # Ensure gridliners were plotted
+    for ax in fig.axes:
+        for gl in ax._gridliners:
+            assert hasattr(gl, '_plotted') and gl._plotted
+
+
 @pytest.mark.natural_earth
 @ImageTesting([grid_label_inline_image], tolerance=grid_label_inline_tol)
 def test_grid_labels_inline():