plugins: do not advance stages before env start

[scztt]

If env has not been triggered for the first time, don't advance to the next segment. Set the initial shape to hold, so that we hold the first envelope value before start. Fixes #334

[scztt]

It would be good to have a couple people take a look at this, and cross-test it with some of the other envgen bugs as well. It fixes the case in question but envgen is a complex ugen and very at risk of other breakages....

[crucialfelix]

has conflicts, should be easy to fix up

[crucialfelix]

I built a new up to date PR with this code to test. Will push that and close this when I've figured it out.

Some of the parts of this PR were merged in at a later date, but not the critical line that turns it on.

// this fixes doneAction 14, but breaks with EnvGen_next_aa

[vivid-synth]

Nit: can you change the spaces to tabs to stay consistent?

[crucialfelix]

yep, my editor already did that for me :) I haven't pushed the PR up yet

[crucialfelix]

This introduced a bug where EnvGen.ar would not work:

// EnvGen.ar should continue to work.
// this should play the SinOsc
{ SinOsc.ar(440, 0, EnvGen.ar(Env([0, 1, 0],[0, 0.5], -3), Impulse.ar(1))) }.play

and was reverted for the 3.7.2 release 0f69855

The other minor refactoring in this PR did make it in and are fine.

[crucialfelix]

I've checked through this. As noted, some parts of it are merged already; one part introduced a bug.

and actually it doesn't seem to fix the pause bug:

SynthDef(\pausefail, { |gate = 0|
    var freq_eg = EnvGen.kr(
        Env([200, 400, 300], [2, 2], \exp, releaseNode: 1),
        gate,
        doneAction: 1
    );
    Poll.kr(2, freq_eg);
}).add;

f = { |msg|
    if(#['/n_go', '/n_end', '/n_on', '/n_off'].includes(msg[0])) {
        msg.postln;
    };
};

thisProcess.addOSCRecvFunc(f);

// this should pause the synth immediately
// because it starts with gate 0
a = Synth(\pausefail, [gate: 0]);
// but you will see Poll will continue to post showing that the synth is not paused

/*
-> Synth('pausefail' : 1000)
UGen(EnvGen): 200
[ /n_go, 1000, 1, -1, -1, 0 ]
UGen(EnvGen): 200
UGen(EnvGen): 200
UGen(EnvGen): 200
UGen(EnvGen): 200
UGen(EnvGen): 200
UGen(EnvGen): 200
UGen(EnvGen): 200
UGen(EnvGen): 200
UGen(EnvGen): 200
UGen(EnvGen): 200
UGen(EnvGen): 200
UGen(EnvGen): 200
UGen(EnvGen): 200
UGen(EnvGen): 200
*/

a.run(false);  // /n_off, correctly, and Poll stops
a.run(true);   // /n_on, correctly, and Poll resumes

a.set(\gate, 1);  // polled value increases

a.set(\gate, 0);  // polled value decreases and node pauses (OK)

a.free;

Or maybe that is what is supposed to do: keep playing until it gets a gate that goes from positive to 0 and then pause.

To experiment with this you can go to https://github.com/supercollider/supercollider/blob/master/server/plugins/LFUGens.cpp#L2818
and just uncomment that line.

There is nothing else in this PR besides that.