indicate_inset transform support

Author: rcomer

lib/matplotlib/axes/_axes.py

@@ -440,7 +440,7 @@ def indicate_inset(self, bounds=None, inset_ax=None, *, transform=None,
 
         transform : `.Transform`
             Transform for the rectangle coordinates. Defaults to
-            ``ax.transAxes``, i.e. the units of *rect* are in Axes-relative
+            ``ax.transData``, i.e. the units of *rect* are in the Axes' data
             coordinates.
 
         facecolor : :mpltype:`color`, default: 'none'

lib/matplotlib/inset.py

@@ -79,6 +79,13 @@ def _shared_setter(self, prop, val):
 
         artist.setp([self._rectangle, *self._connectors], prop, val)
 
+    @artist.Artist.axes.setter
+    def axes(self, new_axes):
+        # Set axes on the rectangle (required for some external transforms to work) as
+        # well as the InsetIndicator artist.
+        self.rectangle.axes = new_axes
+        artist.Artist.axes.fset(self, new_axes)
+
     def set_alpha(self, alpha):
         # docstring inherited
         self._shared_setter('alpha', alpha)
@@ -171,7 +178,7 @@ def _update_connectors(self):
                 # parent artist.
                 p = ConnectionPatch(
                     xyA=xy_inset_ax, coordsA=self._inset_ax.transAxes,
-                    xyB=xy_data, coordsB=self.axes.transData,
+                    xyB=xy_data, coordsB=self.rectangle.get_data_transform(),
                     arrowstyle="-",
                     edgecolor=self._edgecolor, alpha=self.get_alpha(),
                     linestyle=self._linestyle, linewidth=self._linewidth)
@@ -182,7 +189,7 @@ def _update_connectors(self):
                 existing.xy1 = xy_inset_ax
                 existing.xy2 = xy_data
                 existing.coords1 = self._inset_ax.transAxes
-                existing.coords2 = self.axes.transData
+                existing.coords2 = self.rectangle.get_data_transform()
 
         if existing is None:
             # decide which two of the lines to keep visible....

lib/matplotlib/tests/baseline_images/test_inset/zoom_inset_transform.png

@@ -4,6 +4,7 @@
 
 import matplotlib.colors as mcolors
 import matplotlib.pyplot as plt
+import matplotlib.transforms as mtransforms
 from matplotlib.testing.decorators import image_comparison, check_figures_equal
 
 
@@ -104,3 +105,38 @@ def test_zoom_inset_connector_styles():
     # Make one visible connector a different style
     indicator.connectors[1].set_linestyle('dashed')
     indicator.connectors[1].set_color('blue')
+
+
+@image_comparison(['zoom_inset_transform.png'], remove_text=True, style='mpl20',
+                  tol=0.01)
+def test_zoom_inset_transform():
+    fig, ax = plt.subplots()
+
+    ax_ins = ax.inset_axes([0.2, 0.2, 0.3, 0.15])
+    ax_ins.set_ylim([0.3, 0.6])
+    ax_ins.set_xlim([0.5, 0.9])
+
+    tr = mtransforms.Affine2D().rotate_deg(30)
+    indicator = ax.indicate_inset_zoom(ax_ins, transform=tr + ax.transData)
+    for conn in indicator.connectors:
+        conn.set_visible(True)
+
+
+def test_zoom_inset_external_transform():
+    # Smoke test that an external transform that requires an axes (i.e.
+    # Cartopy) will work.
+    class FussyDataTr:
+        def _as_mpl_transform(self, axes=None):
+            if axes is None:
+                raise ValueError("I am a fussy transform that requires an axes")
+            return axes.transData
+
+    fig, ax = plt.subplots()
+
+    ax_ins = ax.inset_axes([0.2, 0.2, 0.3, 0.15])
+    ax_ins.set_xlim([0.7, 0.8])
+    ax_ins.set_ylim([0.7, 0.8])
+
+    ax.indicate_inset_zoom(ax_ins, transform=FussyDataTr())
+
+    fig.draw_without_rendering()