Clarify that pycairo>=1.14.0 is needed. (#23843)

anntzer · web-flow · commit a7e553de10e6 · 2022-09-09T15:50:08.000+02:00
This is simply documenting the status quo and putting an earlier check
for it (rather than erroring out with an AttributeError at runtime), so
no changelog.

Also, technically, only the gtk backends need pycairo 1.14 (the other
backends can stick to 1.11), but 1.14 is old enough (2017) that it
doesn't seem worth the complication of having two different bounds.
diff --git a/doc/devel/dependencies.rst b/doc/devel/dependencies.rst
@@ -47,12 +47,11 @@ and the capabilities they provide.
   most standard Python installations, but it's not part of Python itself and
   thus may not be present in rare cases.
 * PyQt6_ (>= 6.1), PySide6_, PyQt5_, or PySide2_: for the Qt-based backends.
-* PyGObject_: for the GTK-based backends. If using pip (but not conda or system
-  package manager) PyGObject must be built from source; see `pygobject
-  documentation
+* PyGObject_ and pycairo_ (>= 1.14.0): for the GTK-based backends. If using pip
+  (but not conda or system package manager) PyGObject must be built from
+  source; see `pygobject documentation
   <https://pygobject.readthedocs.io/en/latest/devguide/dev_environ.html>`_.
-* pycairo_ (>= 1.11.0) or cairocffi_ (>= 0.8): for the GTK and/or cairo-based
-  backends.
+* pycairo_ (>= 1.14.0) or cairocffi_ (>= 0.8): for cairo-based backends.
 * wxPython_ (>= 4): for the wx-based backends.  If using pip (but not conda or
   system package manager) on Linux wxPython wheels must be manually downloaded
   from https://wxpython.org/pages/downloads/.
diff --git a/lib/matplotlib/backends/backend_cairo.py b/lib/matplotlib/backends/backend_cairo.py
@@ -14,15 +14,14 @@
 
 try:
     import cairo
-    if cairo.version_info < (1, 11, 0):
-        # Introduced create_for_data for Py3.
+    if cairo.version_info < (1, 14, 0):  # Introduced set_device_scale.
         raise ImportError
 except ImportError:
     try:
         import cairocffi as cairo
     except ImportError as err:
         raise ImportError(
-            "cairo backend requires that pycairo>=1.11.0 or cairocffi "
+            "cairo backend requires that pycairo>=1.14.0 or cairocffi "
             "is installed") from err
 
 import matplotlib as mpl
