Move deprecation as suggested by @OceanWolf

matplotlib · tacaswell · Jun 29, 2016 · Jun 10, 2016 · Jun 10, 2016 · Jun 10, 2016
commit 90c4f60df934193c561c4b243c29c7106de9f359
diff --git a/lib/matplotlib/backends/backend_gdk.py b/lib/matplotlib/backends/backend_gdk.py
@@ -434,19 +434,18 @@ def new_figure_manager_given_figure(num, figure):
 class FigureCanvasGDK (FigureCanvasBase):
    def __init__(self, figure):
        FigureCanvasBase.__init__(self, figure)
-
+        if self.__class__ == matplotlib.backends.backend_gdk.FigureCanvasGDK:
+            warn_deprecated('2.0', message="The GDK backend is "
+                            "deprecated. It is untested, known to be "
+                            "broken and will be removed in Matplotlib 2.2. "
+                            "Use the Agg backend instead.",
+                            alternative="Agg")
        self._renderer_init()

    def _renderer_init(self):
        self._renderer = RendererGDK (gtk.DrawingArea(), self.figure.dpi)

    def _render_figure(self, pixmap, width, height):
-        if isinstance(self._renderer, RendererGDK):
-            warn_deprecated('2.0', message="The GDK backend is "
-                            "deprecated. It is untested, known to be "
-                            "broken and will be removed in Matplotlib 2.2. "
-                            "Use the Agg backend instead.",
-                            alternative="Agg")
        self._renderer.set_pixmap (pixmap)
        self._renderer.set_width_height (width, height)
        self.figure.draw (self._renderer)

diff --git a/lib/matplotlib/backends/backend_gtk.py b/lib/matplotlib/backends/backend_gtk.py
@@ -213,6 +213,12 @@ class FigureCanvasGTK (gtk.DrawingArea, FigureCanvasBase):
                  gdk.POINTER_MOTION_HINT_MASK)

    def __init__(self, figure):
+        if self.__class__ == matplotlib.backends.backend_gtk.FigureCanvasGTK:
+            warn_deprecated('2.0', message="The GTK backend is "
+                            "deprecated. It is untested, known to be "
+                            "broken and will be removed in Matplotlib 2.2. "
+                            "Use the GTKAgg backend instead.",
+                            alternative="GTKAgg")
        if _debug: print('FigureCanvasGTK.%s' % fn_name())
        FigureCanvasBase.__init__(self, figure)
        gtk.DrawingArea.__init__(self)
@@ -419,12 +425,6 @@ def _pixmap_prepare(self, width, height):
    def _render_figure(self, pixmap, width, height):
        """used by GTK and GTKcairo. GTKAgg overrides
        """
-        if isinstance(self._renderer, RendererGDK):
-            warn_deprecated('2.0', message="The GTK backend is "
-                            "deprecated. It is untested, known to be "
-                            "broken and will be removed in Matplotlib 2.2. "
-                            "Use the GTKAgg backend instead.",
-                            alternative="GTKAgg")
        self._renderer.set_width_height (width, height)
        self.figure.draw (self._renderer)