Add cairo_device_t

The device is a generic method for accessing the underlying interface
with the native graphics subsystem, typically the X connection or
perhaps the GL context. By exposing a cairo_device_t on a surface and
its various methods we enable finer control over interoperability with
external interactions of the device by applications. The use case in
mind is, for example, a multi-threaded gstreamer which needs to serialise
its own direct access to the device along with Cairo's across many
threads.

Secondly, the cairo_device_t is a unifying API for the mismash of
backend specific methods for controlling creation of surfaces with
explicit devices and a convenient hook for debugging and introspection.

The principal components of the API are the memory management of:

  cairo_device_reference(),
  cairo_device_finish() and
  cairo_device_destroy();

along with a pair of routines for serialising interaction:

  cairo_device_acquire() and
  cairo_device_release()

and a method to flush any outstanding accesses:

  cairo_device_flush().

The device for a particular surface may be retrieved using:

  cairo_surface_get_device().

The device returned is owned by the surface.

1 files changed, 7 insertions, 2 deletions

diff --git a/src/cairo-analysis-surface.c b/src/cairo-analysis-surface.c
index b777abc1..1922bc50 100644
--- a/src/cairo-analysis-surface.c
+++ b/src/cairo-analysis-surface.c
@@ -717,7 +717,9 @@ _cairo_analysis_surface_create (cairo_surface_t		*target)
 
     /* I believe the content type here is truly arbitrary. I'm quite
      * sure nothing will ever use this value. */
-    _cairo_surface_init (&surface->base, &cairo_analysis_surface_backend,
+    _cairo_surface_init (&surface->base,
+			 &cairo_analysis_surface_backend,
+			 NULL, /* device */
 			 CAIRO_CONTENT_COLOR_ALPHA);
 
     cairo_matrix_init_identity (&surface->ctm);
@@ -907,7 +909,10 @@ _cairo_null_surface_create (cairo_content_t content)
 	return _cairo_surface_create_in_error (_cairo_error (CAIRO_STATUS_NO_MEMORY));
     }
 
-    _cairo_surface_init (surface, &cairo_null_surface_backend, content);
+    _cairo_surface_init (surface,
+			 &cairo_null_surface_backend,
+			 NULL, /* device */
+			 content);
 
     return surface;
 }