[LV2] New method "slider" to lv2 specification

[Robin Gareus]

On 7/14/20 11:16 AM, MAXIPENNA at libero.it wrote:
> The coefficients need to be changed when you rotate the "Freq" knob.
> In all the lv2 examples I've found, all the coeffs are re-calculated
> in the "run" method but, from what I know, it's wrong. In the run
> method I should execute only the code that implements the biquad
> cell.

In order to be able to provide a click-free transition when a parameter
changes, recalculating the coefficients must happen synchronous to
processing.

This is usually an iterative process that involves interpolation, and
since this has to be independently of the process block-size, the
process callback is the only place where this can be done.

This concept is common to all major plugin standards.

ciao,
robin