"Fix" tight_layout for template backend.

anntzer · anntzer · commit 9610a5008459 · 2020-06-24T11:59:33.000+02:00
We rely on print_foo actually walking through the Figure tree (which any
non-trivial canvas should likely do...).
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -1552,8 +1552,10 @@ def _draw(renderer): raise Done(renderer)
             print_method(io.BytesIO(), dpi=figure.dpi)
         except Done as exc:
             renderer, = figure._cachedRenderer, = exc.args
-
-    return renderer
+            return renderer
+        else:
+            raise RuntimeError(f"{print_method} did not call Figure.draw, so "
+                               f"no renderer is available")
 
 
 def _is_non_interactive_terminal_ipython(ip):
diff --git a/lib/matplotlib/backends/backend_template.py b/lib/matplotlib/backends/backend_template.py
@@ -208,6 +208,7 @@ def print_foo(self, filename, *args, **kwargs):
         to their original values after this call, so you don't need to
         save and restore them.
         """
+        self.draw()
 
     def get_default_filetype(self):
         return 'foo'
