Fix PdfPages+cairo.

anntzer · anntzer · commit 697f4792a259 · 2017-08-29T01:53:54.000-07:00
... by forcing pdf backend output from within PdfPages.
diff --git a/lib/matplotlib/backend_bases.py b/lib/matplotlib/backend_bases.py
@@ -2093,27 +2093,33 @@ def get_supported_filetypes_grouped(cls):
             groupings[name].sort()
         return groupings
 
-    def _get_output_canvas(self, format):
-        """Return a canvas that is suitable for saving figures to a specified
-        file format. If necessary, this function will switch to a registered
-        backend that supports the format.
+    def _get_output_canvas(self, fmt):
         """
-        method_name = 'print_%s' % format
+        Return a canvas suitable for saving figures to a specified file format.
 
-        # check if this canvas supports the requested format
-        if hasattr(self, method_name):
+        If necessary, this function will switch to a registered backend that
+        supports the format.
+        """
+        method_name = 'print_%s' % fmt
+
+        # Return the current canvas if it supports the requested format.  Note
+        # that we explicitly support setting print_foo to None to remove
+        # support for a format; this is required for PdfPages to work while the
+        # current backend supports pdf output (because PdfPages is tightly
+        # coupled with backend_pdf).  This feature may be removed if PdfPages
+        # gets decoupled from backend_pdf.
+        if getattr(self, method_name, None) is not None:
             return self
 
-        # check if there is a default canvas for the requested format
-        canvas_class = get_registered_canvas_class(format)
+        # Return a default canvas for the requested format, if it exists.
+        canvas_class = get_registered_canvas_class(fmt)
         if canvas_class:
             return self.switch_backends(canvas_class)
 
-        # else report error for unsupported format
-        formats = sorted(self.get_supported_filetypes())
-        raise ValueError('Format "%s" is not supported.\n'
-                         'Supported formats: '
-                         '%s.' % (format, ', '.join(formats)))
+        # Else report error for unsupported format.
+        raise ValueError(
+            "Format {!r} is not supported (supported formats: {})"
+            .format(fmt, ", ".join(sorted(self.get_supported_filetypes()))))
 
     def print_figure(self, filename, dpi=None, facecolor=None, edgecolor=None,
                      orientation='portrait', format=None, **kwargs):
diff --git a/lib/matplotlib/backends/backend_pdf.py b/lib/matplotlib/backends/backend_pdf.py
@@ -2523,18 +2523,20 @@ def savefig(self, figure=None, **kwargs):
             instance is provided, this figure is saved. If an int is specified,
             the figure instance to save is looked up by number.
         """
-        if isinstance(figure, Figure):
-            figure.savefig(self, format='pdf', **kwargs)
-        else:
+        if not isinstance(figure, Figure):
             if figure is None:
-                figureManager = Gcf.get_active()
-            else:
-                figureManager = Gcf.get_fig_manager(figure)
-            if figureManager is None:
-                raise ValueError("No such figure: " + repr(figure))
+                manager = Gcf.get_active()
             else:
-                figureManager.canvas.figure.savefig(self, format='pdf',
-                                                    **kwargs)
+                manager = Gcf.get_fig_manager(figure)
+            if manager is None:
+                raise ValueError("No figure {}".format(figure))
+            figure = manager.canvas.figure
+        # Force use of pdf backend, as PdfPages is tightly coupled with it.
+        try:
+            figure.canvas = FigureCanvasPdf(figure)
+            figure.savefig(self, format="pdf", **kwargs)
+        finally:
+            figure.canvas = manager.canvas
 
     def get_pagecount(self):
         """
