[gmpi] Re: Decision time: 8.1

On Sat, Aug 16, 2003 at 09:16:21AM +1200, Jeff McClintock wrote:
> > Because there are likely to be more than a single interface for a
> Parameter
> > (e.g. GUI and motorized MIDI control), the current state of a Parameter
> must
> > be sent to all listeners when that state changes.
> >
> >    "A Parameter can have multiple listeners, which are notified upon state
> >    changes."
> 
> 
> Yes, but....There is the question: Is this better handled by the host, or by
> the plugin?
> 
> Can I sugest a simplification?
> 
> Only the host can get/set the parameter.  From the plugin's point-of-view,
> it dosn't have multiple listeners.
>   BUT, the host can then expose that Parameter to multiple devices (A
> hardware controller plus a On-screen Slider plus a Controller automation
> track etc)....

Sure, that might be reasonable.  Being totally abstract about it, the
statement is correct.  I never necessitated that the plugin be responsible
for notifications. :)  But yes, I think you are correct.  There is the
further question - does the host have to manage all events?

Let me make an example that I think will clarify.  Plugin_A has a
Control-Out and we want to send the values to Plugin_B's Control-In.  There
are two options.

a) Send the output to the host, who will redirect it where it is needed, and
update all listeners with the new value.

b) Send it directly, and let Plugin_B send a different message to the host
saying "my value has changed to X".  This has the advantage of letting the
plugin react to values, rather than us just assuming they did.  For some
contrived examples: changing one control might force another to change
internally, or the plugin could be dynamically changing parameters itself.

I also neglected to point out that even if a parameter is input only, you
can still read it's value.  This is contrary to what we did in XAP, which I
never quite liked.  In XAP, you knew the value of a parameter because you
snooped it's input stream (similar to option a).  There was no way to
directly query a control.

-- 
Notice that as computers are becoming easier and easier to use,
suddenly there's a big market for "Dummies" books.  Cause and effect,
or merely an ironic juxtaposition of unrelated facts?


----------------------------------------------------------------------
Generalized Music Plugin Interface (GMPI) public discussion list
Participation in this list is contingent upon your abiding by the
following rules:  Please stay on topic.  You are responsible for your own
words.  Please respect your fellow subscribers.  Please do not
redistribute anyone else's words without their permission.

Archive: http://www.freelists.org/archives/gmpi
Email gmpi-request@xxxxxxxxxxxxx w/ subject "unsubscribe" to unsubscribe

Other related posts: