[gst-devel] Re: [gst-cvs] jdahlin gst-plugins: gst-plugins/ gst-plugins/sys/v4l/

[Ronald Bultje]

Hi,

On Fri, 13 Aug 2004, Johan Dahlin wrote:
> > And how do we do runtime checks then? That's what GstImplementsInterface
> > solves. Nothing more than that. GInterface doesn't solve it, so we need
> > something else. What alternative solution did you have in mind?
>
> enum + set accessor:
>
> typedef enum {
>   GST_V4LSRC_SUPPORTS_OVERLAY ...
>   GST_V4LSRC_SUPPORTS_TUNER   ...
>   ....
> } GstV4lFeaturesMask;
>
> Public getter:
>
> GstV4lFeaturesMask gst_v4lsrc_get_features (GstV4lsrc *)
>
> and a private setter
>
> So if the user tries to call a xoverlay function on an element not
> support it, it should either silently return a bad value or
>  (preferably) raise an error of some kind, that can be catched by user
> code.

That's insane. We're not at all talking about v4l here, but about the
tuner interface which might or might not be implemented by element X,
which could be v4lsrc, bktrsrc, xsrc, v4l2src, directxsrc or whatever
other element you had in mind. Implementation is part of the interface (or
a dependency, which GstImplementsInterface is) or it's not there at all.

And in the end, you still need to do a runtime check which we currently do
as well, so apart from being more messy there's no difference between your
proposed way and the current way.

Ronald