RFC Patch: new public API to manipulate default modulators

[derselbst]

When using FluidSynth as a custom synthesizer, developers sometimes need (or want) to use other default modulators than the standard ones defined in the SoundFont spec. Currently the only way to modify the default modulators is to write a custom soundfont loader or override the default modulators in all used soundfonts.

This patch proposes a new public API to manipulate the default modulators. I would be very grateful for feedback on this approach. Is opening up the default modulator list like this acceptable for you, the maintainers of fluidsynth?

Here is an example to use the new API (adding a new default modulator on Key Pressure, introduced in the patch for ticket #50):

   ...
  settings = new_fluid_settings();
  ...
  synth = new_fluid_synth(settings);
  // Add a Key Pressure to Initial Attenuation modulator
  mod = fluid_mod_new();
  fluid_mod_set_source1(mod,
          FLUID_MOD_KEYPRESSURE,
          FLUID_MOD_GC |
          FLUID_MOD_NEGATIVE |
          FLUID_MOD_UNIPOLAR |
          FLUID_MOD_CONCAVE);
  fluid_mod_set_source2(mod, 0, 0);
  fluid_mod_set_dest(mod, GEN_ATTENUATION);
  fluid_mod_set_amount(mod, 960.0);

  fluid_synth_add_default_mod(synth, mod, FLUID_SYNTH_ADD);
  adriver = new_fluid_audio_driver(settings, synth);
  ...

Reported by: mawe242

Original Ticket: fluidsynth/tickets/166

[derselbst]

Just to be clear: the new API call is:

fluid_synth_add_default_mod(synth, mod, FLUID_SYNTH_ADD);

Original comment by: mawe242

[derselbst]

Following up from the discussion on the fluid-dev mailing list, here is version 2 of the patch with the static list of modulators replaced with a dynamically allocated one.

Original comment by: mawe242

[derselbst]

Addresses #71.