Tell IPython the correct GUI event loop to use for all backends.

anntzer · anntzer · commit ac93ecf90b43 · 2018-11-04T10:33:03.000+01:00
IPython currently uses a hard-coded table
(IPython.core.pylabtools.backend2gui) to know which event loop to use
for which backend.  This approach fails for both the new builtin
cairo-based backends (which do not appear in the table), and for
third-party backends (e.g. mplcairo).

mplcairo has used some custom code to patch that table for a while;
reuse it to more generally use the new "required_interactive_framework"
attribute.

Note that this PR suggests that there should be a better way to go back
from the canvas class to the backend module (rather than looking for
`sys.modules[cls.__module__].required_interactive_framework`, which is a
bit hacky and could in theory fail if the canvas class is actually
defined in another submodule).
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -33,6 +33,7 @@
 """
 
 from contextlib import contextmanager
+import functools
 import importlib
 import io
 import os
@@ -43,6 +44,7 @@
 
 import numpy as np
 
+import matplotlib as mpl
 from matplotlib import (
     backend_tools as tools, cbook, colors, textpath, tight_bbox, transforms,
     widgets, get_backend, is_interactive, rcParams)
@@ -1613,6 +1615,7 @@ class FigureCanvasBase(object):
                          'Tagged Image File Format')
 
     def __init__(self, figure):
+        self._fix_ipython_backend2gui()
         self._is_idle_drawing = True
         self._is_saving = False
         figure.set_canvas(self)
@@ -1629,6 +1632,35 @@ def __init__(self, figure):
         self.toolbar = None  # NavigationToolbar2 will set me
         self._is_idle_drawing = False
 
+    @classmethod
+    @functools.lru_cache()
+    def _fix_ipython_backend2gui(cls):
+        # Fix hard-coded module -> toolkit mapping in IPython (used for
+        # `ipython --auto`).  This cannot be done at import time due to
+        # ordering issues, so we do it when creating a canvas, and should only
+        # be done once per class (hence the `lru_cache(1)`).
+        if "IPython" not in sys.modules:
+            return
+        import IPython
+        ip = IPython.get_ipython()
+        if not ip:
+            return
+        from IPython.core import pylabtools as pt
+        backend_mod = sys.modules[cls.__module__]
+        rif = getattr(backend_mod, "required_interactive_framework", None)
+        backend2gui_rif = {"qt5": "qt", "qt4": "qt", "gtk3": "gtk3",
+                           "wx": "wx", "macosx": "osx"}.get(rif)
+        if backend2gui_rif:
+            pt.backend2gui[get_backend()] = backend2gui_rif
+            # Work around pylabtools.find_gui_and_backend always reading from
+            # rcParamsOrig.
+            orig_origbackend = mpl.rcParamsOrig["backend"]
+            try:
+                mpl.rcParamsOrig["backend"] = mpl.rcParams["backend"]
+                ip.enable_matplotlib()
+            finally:
+                mpl.rcParamsOrig["backend"] = orig_origbackend
+
     @contextmanager
     def _idle_draw_cntx(self):
         self._is_idle_drawing = True
