Deprecate the backend.qt{4,5} rcParams.

anntzer · anntzer · commit 0efd32d68273 · 2018-01-21T16:09:38.000-08:00
1) For the rcParams rewrite (MEP32), they may make it tricky to
transform rcParams into a nested dictionary type of object, as "backend"
is already the name of another (more important) rcParam.  This specific
issue could be solved with deprecation + renaming, but also...

2) The use of these rcParams can easily be replaced by a) first
importing one of the bindings (qt_compat will ensure that the already
imported binding gets used, as importing multiple bindings in the same
process is a bad idea anyways), or b) setting the QT_API environment
variable appropriately.
diff --git a/lib/matplotlib/__init__.py b/lib/matplotlib/__init__.py
@@ -847,11 +847,13 @@ def gen_candidates():
 
 _obsolete_set = {'text.dvipnghack'}
 
+_other_deprecated = {'backend.qt4', 'backend.qt5'}
+
 # The following may use a value of None to suppress the warning.
 _deprecated_set = {'axes.hold'}  # do NOT include in _all_deprecated
 
 _all_deprecated = set(itertools.chain(
-    _deprecated_ignore_map, _deprecated_map, _obsolete_set))
+    _deprecated_ignore_map, _deprecated_map, _obsolete_set, _other_deprecated))
 
 
 class RcParams(MutableMapping, dict):
diff --git a/lib/matplotlib/rcsetup.py b/lib/matplotlib/rcsetup.py
@@ -266,8 +266,20 @@ def validate_backend(s):
         return _validate_standard_backends(s)
 
 
-validate_qt4 = ValidateInStrings('backend.qt4', ['PyQt4', 'PySide', 'PyQt4v2'])
-validate_qt5 = ValidateInStrings('backend.qt5', ['PyQt5', 'PySide2'])
+@deprecated("2.2",
+            "The backend.qt4 rcParam was deprecated in version 2.2.  In order "
+            "to force the use of a specific Qt4 binding, either import that "
+            "binding first, or set the QT_API environment variable.")
+def validate_qt4(s):
+    return s in ['PyQt4', 'PySide', 'PyQt4v2']
+
+
+@deprecated("2.2",
+            "The backend.qt5 rcParam was deprecated in version 2.2.  In order "
+            "to force the use of a specific Qt5 binding, either import that "
+            "binding first, or set the QT_API environment variable.")
+def validate_qt5(s):
+    return s in ['PyQt5', 'PySide2']
 
 
 def validate_toolbar(s):
