plotters: Adjust to new renderer handling in Matplotlib 3.6

The handling of the internal renderer objects changed in Matplotlib 3.6, and we
haven't adjusted to the new API. Move the existing logic into a helper function
so we can use it consistently, and try calling the new matplotlib API before
falling back to the old logic.

Fixes #291.

Signed-off-by: Toke Høiland-Jørgensen <[email protected]>

flent/plotters.py

@@ -952,14 +952,32 @@ def save_pdf(self, filename, data_filename, save_args):
         finally:
             pdf.close()
 
+    def _get_renderer(self):
+
+        # Matplotlib 3.6 reorganised the renderer caching logic and introduced
+        # the _get_renderer() method of the figure class, so try that first
+        try:
+            return self.figure._get_renderer()
+        except AttributeError:
+            pass
+
+        # Older versions of matplotlib cached the renderer in the figure itself,
+        # but it may not exist until after figure is drawn
+        renderer = getattr(self.figure, '_cachedRenderer', None)
+        if not renderer:
+            self.figure.canvas.draw()
+            renderer = getattr(self.figure, '_cachedRenderer', None)
+
+        return renderer
+
     def build_tight_layout(self, artists):
         args = None
         if self.fallback_layout:
             return {'bbox_extra_artists': artists, 'bbox_inches': 'tight'}
         try:
             self.figure.savefig(io.BytesIO())
 
-            renderer = self.figure._cachedRenderer
+            renderer = self._get_renderer()
             right = x_max = self.figure.get_figwidth() * self.figure.dpi
             top = y_max = self.figure.get_figheight() * self.figure.dpi
             vsp = 0.02 * self.figure.dpi
@@ -1038,15 +1056,9 @@ def size_legends(self, event=None):
            and not self.legend_placement \
            and self.legends:
 
-            # Make sure we have a renderer to get size from
-            renderer = getattr(self.figure, '_cachedRenderer', None)
-            if not renderer:
-                self.figure.canvas.draw()
-                renderer = getattr(self.figure, '_cachedRenderer', None)
-
             try:
                 legend_width = max(
-                    [l.get_window_extent(renderer).width for l in self.legends])
+                    [l.get_window_extent(self._get_renderer()).width for l in self.legends])
             except Exception as e:
                 logger.debug("Error getting legend sizes: %s", e)
                 return