not sure why trigger does't work here (see Latch)

gistfile1.sc

~grain_reveal = NodeDef {
    arg buf, interval = 0.02, dur = 0.1,
    threshold = 0.002, grow = 0.7, attack = 3, decay = 15,
    in, trigger;

    var energy, sound;

    energy = (in - threshold).max(0) * grow;
    energy = Decay2.kr(energy, attack, decay).min(1.0);

    sound = GrainBuf.ar (
        2,
        TDuty.ar(Dwhite(interval * 0.3, interval * 1.8)),
        dur,
        buf,
        BufRateScale.ir(buf),
        // LFNoise1.kr(0.01) * 0.5 + 0.5;
	LFSaw.kr(LFPulse.ar(0.25,0,0.01) + 0.001 * 0.9 );
	// Latch.kr( WhiteNoise.kr(), trigger) // ??????????
	/// why this doesn't work as with grain_trigger_env???
    );
    sound = LPF.ar( sound, energy.pow(4) * 20000 + 200 ) * ((energy * 4).min(1) + 0.01) * 0.8;
    // Reverse filter and amp:
    /*
    x = (
        LPF.ar( x, (1 - movement).pow(4) * 20000 + 200 )
        * ( (1 - (movement * 1)).max(0) + 0.01)
        * 0.5;
    )
    */
};

"trigger" is here an argument to the NodeDef function -> it becomes a input to the node.
It has to be mapped to the preprocessing node that produces the trigger, equivalently to:

~grain_trigger_env.map(\trigger, [~trigger, 0]);

where:

• "\trigger" refers to the argument of the "~grain_trigger_env" NodeDef
• "~trigger" refers to the trigger-producing (preprocessing) NodeDef.
• "0" refers to the first output of the trigger-producing NodeDef