[Spice-devel] [PATCH 09/14] server: make cursor channel private

[Frediano Ziglio]

> 
> On Fri, Oct 23, 2015 at 10:29:04AM -0400, Frediano Ziglio wrote:
> > It would be much better to define a public structure like
> > 
> > struct CursorChannel {
> >    CommonChannel common;
> > };
> > 
> > and a private one (in cursor-channel.c) like
> > 
> > struct CursorChannel {
> >    CommonChannel common;
> >    ... any field needed ...
> > }
> > 
> > and define the macro as
> > 
> > #define RED_CHANNEL(Channel) (&(Channel)->common.base)
> 
> This kind of macros does not work as soon as you introduce another level
> of inheritance:
> 
> struct SpecializedCursorChannel {
>     CursorChannel parent;
>     /* more stuff */
> };
> 
> You cannot use your RED_CHANNEL macro to get a RedChannel from a
> SpecializedCursorChannel instance.
> 
> Christophe
> 

Yes, this does not prevent the macro to convert an integer array to a RedChannel
without warnings. How was implemented before prevented it.
Another was would be adding conversion functions like cursor_channel_get_common_channel.

Frediano