fix matplotlib graphs sometimes not rendering

Author: N-Coder

src/ogdf_python/matplotlib/__init__.py

@@ -20,10 +20,7 @@
 
 
 def repr_mimebundle_GraphAttributes(self, *args, **kwargs):
-    fig = new_figure()
-    ax = fig.subplots()
-    fig.graph = MatplotlibGraph(self, ax)
-    return fig.graph._repr_mimebundle_(*args, **kwargs)
+    return MatplotlibGraph(self)._repr_mimebundle_(*args, **kwargs)
 
 
 def repr_mimebundle_Graph(self, *args, **kwargs):
@@ -40,3 +37,9 @@ def repr_mimebundle_ClusterGraph(self, *args, **kwargs):
 ogdf.Graph._repr_mimebundle_ = repr_mimebundle_Graph
 ogdf.ClusterGraphAttributes._repr_mimebundle_ = repr_mimebundle_GraphAttributes
 ogdf.ClusterGraph._repr_mimebundle_ = repr_mimebundle_ClusterGraph
+
+# ensure that backend is loaded and doesn't reset any configs (esp. is_interactive)
+# when being loaded for the first time
+import matplotlib.pyplot as plt
+
+plt.close(new_figure())

src/ogdf_python/matplotlib/util.py

@@ -326,24 +326,20 @@ def find_closest(GA, x, y, edge_dist=10):
     return None, None, None
 
 
-def new_figure(num=None) -> Figure:
+def new_figure(*args, **kwargs) -> Figure:
+    """ Create a new figure without changing the currently active figure of pyplot """
     import matplotlib.pyplot as plt
     from matplotlib import _pylab_helpers
-    with plt.ioff():
+    plt._get_backend_mod() # make sure backend is loaded before ioff call
+    with plt.ioff(): # disable immediate display of created figures
         old_fig = None
+        # like plt.gcf(), but does not create one if none is active
         manager = _pylab_helpers.Gcf.get_active()
         if manager is not None:
             old_fig = manager.canvas.figure
 
-        fig = plt.figure(num)
+        fig = plt.figure(*args, **kwargs)
 
         if old_fig is not None:
-            plt.figure(old_fig)
+            plt.figure(old_fig) # reactivate the old figure
     return fig
-
-
-# ensure that backend is loaded and doesn't reset any configs (esp. is_interactive)
-# when being loaded for the first time
-import matplotlib.pyplot as plt
-
-plt.close(new_figure())

src/ogdf_python/matplotlib/widget.py

@@ -1,10 +1,10 @@
 import functools
+import sys
 import traceback
+from itertools import chain
 from typing import Dict, Tuple, List
 
 import numpy as np
-import sys
-from itertools import chain
 from matplotlib import patheffects
 from matplotlib.axes import Axes
 from matplotlib.backend_bases import MouseButton
@@ -200,17 +200,24 @@ def _repr_mimebundle_(self, *args, **kwargs):
         if not InteractiveShell.initialized():
             return {"text/plain": repr(self)}, {}
 
+        # larger graphs (see eg `tutorial/4 layouts.ipynb`) sometimes render blank
+        # ensure they are drawn first and spinning the event loop for some time makes that less likely
+        self.ax.figure.canvas.draw()
+        self.ax.figure.canvas.start_event_loop(0.1)
+
         fmt = InteractiveShell.instance().display_formatter
+        # if ipython_display_formatter is enabled, format(figure.canvas) immediately displays and returns None
         display_en = fmt.ipython_display_formatter.enabled
         fmt.ipython_display_formatter.enabled = False
         try:
+            # for interactive backends, we want to render the interactive figure.canvas widget
             data, meta = fmt.format(self.ax.figure.canvas, *args, **kwargs)
-            # print("canvas", list(data.keys()) if data else "none")
+            # for non-interactive backends, this only renders the text/plain repr()
             if list(data.keys()) != ["text/plain"] and data:
                 return data, meta
             else:
+                # so we render the figure instead, which gives a static image
                 data, meta = fmt.format(self.ax.figure, *args, **kwargs)
-                # print("figure", list(data.keys()) if data else "none")
                 return data, meta
         finally:
             fmt.ipython_display_formatter.enabled = display_en