[cairo] surfaces and backends

[Owen Taylor]

On Thu, 2005-03-17 at 00:00 +0800, Steve Chaplin wrote:
> I'd like to implement some new surface methods for pycairo
> surface.set_size()
> surface.set_device_offset()
> 
> They're available for the xlib backend, but not other backends, so I would
> need to check that the surface is an xlib surface.
> Does Cairo provide a direct way to ask a surface which backend it was created for?
> Or is that something a language binding should handle itself (if needed) using
> cairo_surface_set_user_data()?

I think the right way to handle this is in python is with a subclass,
and you have to be able to determine the right subclass on calls like
cairo_get_target_surface()

How do we identify surface types? 
 
 1. Strings. cairo_surface_get_backend_name()

 2. Boolean predicate. cairo_surface_is_xlib()

 3. Opaque type object
    cairo_type_t *cairo_surface_get_type()
    cairo_type_t *cairo_xlib_surface_type()

 4. Global #defines

    #define CAIRO_TYPE_XLIB_SURFACE 1

Not clear to me what's right. Having to reinvent this is the 
not-using-GObject penalty.... :-)

Regards,
					Owen

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