Merge pull request #14795 from anntzer/supports_blit

timhoffm · web-flow · commit 76ecdca817c4 · 2019-07-16T08:51:35.000+02:00
Autodetect whether a canvas class supports blitting.
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -1581,7 +1581,6 @@ class FigureCanvasBase:
         'close_event'
     ]
 
-    supports_blit = True
     fixed_dpi = None
 
     filetypes = _default_filetypes
@@ -1597,6 +1596,11 @@ class FigureCanvasBase:
         register_backend('tiff', 'matplotlib.backends.backend_agg',
                          'Tagged Image File Format')
 
+    @cbook._classproperty
+    def supports_blit(cls):
+        return (hasattr(cls, "copy_from_bbox")
+                and hasattr(cls, "restore_region"))
+
     def __init__(self, figure):
         self._fix_ipython_backend2gui()
         self._is_idle_drawing = True
diff --git a/lib/matplotlib/backends/backend_cairo.py b/lib/matplotlib/backends/backend_cairo.py
@@ -390,7 +390,6 @@ def set_linewidth(self, w):
 
 
 class FigureCanvasCairo(FigureCanvasBase):
-    supports_blit = False
 
     def print_png(self, fobj, *args, **kwargs):
         self._get_printed_image_surface().write_to_png(fobj)
diff --git a/lib/matplotlib/cbook/__init__.py b/lib/matplotlib/cbook/__init__.py
@@ -2131,3 +2131,26 @@ def _check_getitem(_mapping, **kwargs):
         raise ValueError(
             "{!r} is not a valid value for {}; supported values are {}"
             .format(v, k, ', '.join(map(repr, mapping)))) from None
+
+
+class _classproperty:
+    """
+    Like `property`, but also triggers on access via the class, and it is the
+    *class* that's passed as argument.
+
+    Examples
+    --------
+    ::
+        class C:
+            @classproperty
+            def foo(cls):
+                return cls.__name__
+
+        assert C.foo == "C"
+    """
+
+    def __init__(self, fget):
+        self._fget = fget
+
+    def __get__(self, instance, owner):
+        return self._fget(owner)
