Merge pull request matplotlib#24527 from anntzer/showoverride

Fix testing of whether backends use the new pyplot_show API.

Author: oscargus

doc/api/next_api_changes/removals/XXXXX-AL.rst

@@ -0,0 +1,4 @@
+``backend_template.show``
+~~~~~~~~~~~~~~~~~~~~~~~~~
+... has been removed, in order to better demonstrate the new backend definition
+API.

lib/matplotlib/backends/backend_template.py

@@ -136,23 +136,13 @@ class GraphicsContextTemplate(GraphicsContextBase):
 ########################################################################
 
 
-def show(*, block=None):
-    """
-    For image backends - is not required.
-    For GUI backends - show() is usually the last line of a pyplot script and
-    tells the backend that it is time to draw.  In interactive mode, this
-    should do nothing.
-    """
-    for manager in Gcf.get_all_fig_managers():
-        # do something to display the GUI
-        pass
-
-
 class FigureManagerTemplate(FigureManagerBase):
     """
     Helper class for pyplot mode, wraps everything up into a neat bundle.
 
-    For non-interactive backends, the base class is sufficient.
+    For non-interactive backends, the base class is sufficient.  For
+    interactive backends, see the documentation of the `.FigureManagerBase`
+    class for the list of methods that can/should be overridden.
     """
 
 

lib/matplotlib/pyplot.py

@@ -325,8 +325,14 @@ def draw_if_interactive():
     # show is already present, as the latter may be here for backcompat.
     manager_class = getattr(getattr(backend_mod, "FigureCanvas", None),
                             "manager_class", None)
-    if (manager_class.pyplot_show != FigureManagerBase.pyplot_show
-            or show is None):
+    # We can't compare directly manager_class.pyplot_show and FMB.pyplot_show
+    # because pyplot_show is a classmethod so the above constructs are bound
+    # classmethods, & thus always different (being bound to different classes).
+    manager_pyplot_show = vars(manager_class).get("pyplot_show")
+    base_pyplot_show = vars(FigureManagerBase).get("pyplot_show")
+    if (show is None
+            or (manager_pyplot_show is not None
+                and manager_pyplot_show != base_pyplot_show)):
         backend_mod.show = manager_class.pyplot_show
 
     _log.debug("Loaded backend %s version %s.",

lib/matplotlib/tests/test_backend_template.py

@@ -32,9 +32,19 @@ def test_load_old_api(monkeypatch):
 
 def test_show(monkeypatch):
     mpl_test_backend = SimpleNamespace(**vars(backend_template))
-    mock_show = backend_template.FigureManagerTemplate.pyplot_show = \
-        MagicMock()
-    del mpl_test_backend.show
+    mock_show = MagicMock()
+    monkeypatch.setattr(
+        mpl_test_backend.FigureManagerTemplate, "pyplot_show", mock_show)
+    monkeypatch.setitem(sys.modules, "mpl_test_backend", mpl_test_backend)
+    mpl.use("module://mpl_test_backend")
+    plt.show()
+    mock_show.assert_called_with()
+
+
+def test_show_old_global_api(monkeypatch):
+    mpl_test_backend = SimpleNamespace(**vars(backend_template))
+    mock_show = MagicMock()
+    monkeypatch.setattr(mpl_test_backend, "show", mock_show, raising=False)
     monkeypatch.setitem(sys.modules, "mpl_test_backend", mpl_test_backend)
     mpl.use("module://mpl_test_backend")
     plt.show()