Macro synfx_dsp::env_sustain_stage

macro_rules! env_sustain_stage {
    ($state: expr, $stage_idx: expr, $sustain_value: expr, $gate: expr, $else: block) => { ... };
}

Holds the previous state.current value until $gate drops below crate::TRIG_LOW_THRES.

See also EnvState about the first argument $state. $stage_idx is $stage_idx + 1 after this stage is finished.