[LAD] [ann] CAPS 0.4.5

[David Robillard]

On 12/04/11 06:00 AM, Tim Goetze wrote:
> [David Robillard]
>    
>> No, the pragmatic thing to do is not deliberately break your plugin when
>> several knowledgeable people have pointed out that doing so can cause countless
>> problems.
>>      
> Again: not the plugin is broken, but the host that assumes the port
> signature not to change over different plugin versions.
>    
No, a given index on your plugin no longer refers to the same port, 
therefore the interface to the plugin has been broken, period.
> There is no mention of such a requirement in the interface
> specification, therefore the assumption is invalid and the
> responsibility for potential breakage lies with the host.
>    
This "assumption" is obvious, since indices are the ID for a port. To 
argue that this is not true is literally equivalent to arguing that 
LADSPA does not support saving session/patch/etc files in any way, at 
all, whatsoever, since indices are meaningless and can not be relied 
upon to refer to the same port when the plugin is reloaded later.  
Obviously this is absurd.

Your assumption, that hosts must refer to ports by an index within a 
special separate index namespace for control and audio ports, is a much 
greater one: it is not obvious, and the alternative is not absurd. It 
is, in other words, clearly not in the language or spirit of LADSPA. 
There is no reason someone reading ladspa.h and writing an 
implementation would reasonably come to the conclusion that this is the 
required correct behavior.
> It has been shown that properly designed hosts handle the port
> addition just fine.
>    
This is just conveniently, but erroneously, redefining "properly 
designed hosts" to mean "hosts that won't break when I break my plugin 
in this particular way".
> You may of course argue - not entirely unreasonably - that it is more
> pragmatic for the plugin author to cater for broken hosts than to
> expect them to be fixed.  Do you?
>    
No, because the host is not broken, as myself and others (including one 
of the main authors of LADSPA itself, and the main author of the host in 
question) have explained several times over.

You are trying to argue that LADSPA does not present this "assumption" 
that indices refer to a constant port, but as mentioned above, this is 
an obvious conclusion, since the alternative is absurd (ports clearly 
must have /some/ ID). LADSPA certainly does not specify the more complex 
definition of "correct" use of port indices that you are trying to 
justify (nor should it, for several reasons, but that is beside the point).

The simplest, most obvious, and intended rule is: If a given port index 
does not refer to the same port on a new version of a plugin, then the 
plugin interface has broken and the plugin ID MUST be changed. As Fons 
mentioned, this is effectively a different plugin.

Your definition, which splits the port index namespace into two separate 
namespaces, one for control and one for audio, is not obviously intended 
and is not mentioned or alluded to anywhere in LADSPA whatsoever. Hosts 
that do not do this are not broken. That every single host author who 
has participated in this thread agrees, and the fact that you need to 
add a version number so one can kludge around the broken plugin, makes 
that pretty clear...

Cheers,

-dr

P.S. I do empathize with the fact that changing IDs where it /could/ not 
be necessary sucks; this is why LV2 has symbols which are the ID for a 
port instead. However, LADSPA is LADSPA, and doing what you are 
proposing is going to cause real headaches for real people, and would be 
remarkably unskillful given the feedback in this thread... please just 
don't do it :)