Add support for cairocffi.

Author: mdboom

doc/users/whats_new.rst

@@ -149,6 +149,19 @@ added. Furthermore, the the subplottool is now implemented as a modal
 dialog. It was previously a QMainWindow, leaving the SPT open if one closed the
 plotwindow.
 
+Cairo backends
+``````````````
+
+The Cairo backends are now able to use the `cairocffi bindings
+<https://github.com/SimonSapin/cairocffi>`__ which are more actively
+maintained than the `pycairo bindings
+<http://cairographics.org/pycairo/>`__.
+
+Gtk3Agg backend
+```````````````
+
+The Gtk3Agg backend now works on Python 3.x, if the `cairocffi
+bindings <https://github.com/SimonSapin/cairocffi>`__ are installed.
 
 Text
 ----

lib/matplotlib/backends/backend_cairo.py

@@ -30,9 +30,16 @@
 def _fn_name(): return sys._getframe(1).f_code.co_name
 
 try:
-    import cairo
+    import cairocffi as cairo
 except ImportError:
-    raise ImportError("Cairo backend requires that pycairo is installed.")
+    try:
+        import cairo
+    except ImportError:
+        raise ImportError("Cairo backend requires that cairocffi or pycairo is installed.")
+    else:
+        HAS_CAIRO_CFFI = False
+else:
+    HAS_CAIRO_CFFI = True
 
 _version_required = (1,2,0)
 if cairo.version_info < _version_required:
@@ -197,8 +204,14 @@ def draw_text(self, gc, x, y, s, prop, angle, ismath=False, mtext=None):
             if angle:
                 ctx.rotate (-angle * np.pi / 180)
             ctx.set_font_size (size)
-            if isinstance(s, six.text_type):
-                s = s.encode("utf-8")
+
+            if HAS_CAIRO_CFFI:
+                if not isinstance(s, six.text_type):
+                    s = six.text_type(s)
+            else:
+                if isinstance(s, six.text_type):
+                    s = s.encode("utf-8")
+
             ctx.show_text(s)
             ctx.restore()
 
@@ -363,8 +376,8 @@ def set_dashes(self, offset, dashes):
         if dashes == None:
             self.ctx.set_dash([], 0)  # switch dashes off
         else:
-            self.ctx.set_dash (
-               self.renderer.points_to_pixels (np.asarray(dashes)), offset)
+            self.ctx.set_dash(
+                list(self.renderer.points_to_pixels(np.asarray(dashes))), offset)
 
 
     def set_foreground(self, fg, isRGBA=None):

lib/matplotlib/backends/backend_gtk3agg.py

@@ -3,18 +3,20 @@
 
 import six
 
-import cairo
 import numpy as np
 import sys
 import warnings
 
 from . import backend_agg
 from . import backend_gtk3
+from .backend_cairo import cairo, HAS_CAIRO_CFFI
 from matplotlib.figure import Figure
 from matplotlib import transforms
 
-if six.PY3:
-    warnings.warn("The Gtk3Agg backend is not known to work on Python 3.x.")
+if six.PY3 and not HAS_CAIRO_CFFI:
+    warnings.warn(
+        "The Gtk3Agg backend is known to not work on Python 3.x with pycairo. "
+        "Try installing cairocffi.")
 
 
 class FigureCanvasGTK3Agg(backend_gtk3.FigureCanvasGTK3,
@@ -53,8 +55,16 @@ def on_draw_event(self, widget, ctx):
             width = int(bbox.x1) - int(bbox.x0)
             height = int(bbox.y1) - int(bbox.y0)
 
-            image = cairo.ImageSurface.create_for_data(
-                buf, cairo.FORMAT_ARGB32, width, height)
+            if HAS_CAIRO_CFFI:
+                ctx = cairo.Context._from_pointer(
+                    cairo.ffi.cast('cairo_t **',
+                                   id(ctx) + object.__basicsize__)[0],
+                    incref=True)
+                image = cairo.ImageSurface.create_for_data(
+                    buf.data, cairo.FORMAT_ARGB32, width, height)
+            else:
+                image = cairo.ImageSurface.create_for_data(
+                    buf, cairo.FORMAT_ARGB32, width, height)
             ctx.set_source_surface(image, x, y)
             ctx.paint()
 

lib/matplotlib/backends/backend_gtk3cairo.py

@@ -5,10 +5,18 @@
 
 from . import backend_gtk3
 from . import backend_cairo
+from .backend_cairo import cairo, HAS_CAIRO_CFFI
 from matplotlib.figure import Figure
 
 class RendererGTK3Cairo(backend_cairo.RendererCairo):
     def set_context(self, ctx):
+        if HAS_CAIRO_CFFI:
+            ctx = cairo.Context._from_pointer(
+                cairo.ffi.cast(
+                    'cairo_t **',
+                    id(ctx) + object.__basicsize__)[0],
+                incref=True)
+
         self.gc.ctx = ctx
 
 

setupext.py

@@ -1679,9 +1679,12 @@ def get_package_data(self):
 
 def backend_gtk3cairo_internal_check(x):
     try:
-        import cairo
+        import cairocffi
     except ImportError:
-        return (False, "Requires cairo to be installed.")
+        try:
+            import cairo
+        except ImportError:
+            return (False, "Requires cairocffi or pycairo to be installed.")
 
     try:
         import gi
@@ -1871,11 +1874,16 @@ class BackendCairo(OptionalBackendPackage):
 
     def check_requirements(self):
         try:
-            import cairo
+            import cairocffi
         except ImportError:
-            raise CheckFailed("cairo not found")
+            try:
+                import cairo
+            except ImportError:
+                raise CheckFailed("cairocffi or pycairo not found")
+            else:
+                return "pycairo version %s" % cairo.version
         else:
-            return "version %s" % cairo.version
+            return "cairocffi version %s" % cairocffi.version
 
 
 class DviPng(SetupPackage):