linuxaudio.org

On 12/04/11 06:00 AM, Tim Goetze wrote:

quoted text
> [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.

quoted text
> 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.

quoted text
> 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".

quoted text
> 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 :)

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