Bound the automation hold to the window the model has not caught up on, and make that authority model stated, enforced and tested

src/core/instrument/engine/live_params.cpp

@@ -6,7 +6,11 @@
 namespace reasampler::instrument::engine {
 
 LiveValues foldLive(const PlayParams& params, double keyTrack) {
-    LiveValues v;
+    // Value-initialized, so the padding is determinate too. Nothing reads it — the block's
+    // equality is field-wise for exactly that reason — but this is the one construction site
+    // every publisher goes through, and an object with indeterminate bytes travelling under a
+    // seqlock is a hazard worth not having. Off the audio thread; the memset costs nothing here.
+    LiveValues v{};
     v.keyTrack = keyTrack;
     // Folded here, not at the voice: Voice::start reads the block's value directly, so the
     // spline rule has to be applied on the way in or the two would answer differently.
@@ -26,6 +30,48 @@ LiveValues foldLive(const PlayParams& params, double keyTrack) {
     return v;
 }
 
+namespace {
+
+bool sameAdsr(const AdsrParams& a, const AdsrParams& b) {
+    return a.attackFrames == b.attackFrames && a.holdFrames == b.holdFrames &&
+           a.decayFrames == b.decayFrames && a.sustainLevel == b.sustainLevel &&
+           a.releaseFrames == b.releaseFrames && a.attackCurve == b.attackCurve &&
+           a.decayCurve == b.decayCurve && a.releaseCurve == b.releaseCurve;
+}
+
+bool sameAhd(const AhdParams& a, const AhdParams& b) {
+    return a.attackFrames == b.attackFrames && a.decayFrames == b.decayFrames &&
+           a.holdFraction == b.holdFraction && a.attackCurve == b.attackCurve &&
+           a.decayCurve == b.decayCurve;
+}
+
+bool sameFilterSettings(const filter::FilterSettings& a, const filter::FilterSettings& b) {
+    return a.cutoffNorm == b.cutoffNorm && a.resonanceNorm == b.resonanceNorm &&
+           a.morphNorm == b.morphNorm && a.driveNorm == b.driveNorm &&
+           a.morphLaw == b.morphLaw;
+}
+
+}  // namespace
+
+bool operator==(const LiveValues& a, const LiveValues& b) {
+    return sameFilterSettings(a.filterSettings, b.filterSettings) &&
+           a.filterModAmount == b.filterModAmount &&
+           a.filterVelAmount == b.filterVelAmount &&
+           a.filterKeyTrack == b.filterKeyTrack &&
+           sameAdsr(a.filterEnv, b.filterEnv) &&
+           sameAhd(a.filterAhd, b.filterAhd) &&
+           sameAdsr(a.adsr, b.adsr) &&
+           sameAhd(a.ampAhd, b.ampAhd) &&
+           a.pitchEnv.enabled == b.pitchEnv.enabled &&
+           a.pitchEnv.peakSemitones == b.pitchEnv.peakSemitones &&
+           sameAhd(a.pitchEnv.shape, b.pitchEnv.shape) &&
+           a.playRate == b.playRate &&
+           a.pitchOffsetSemitones == b.pitchOffsetSemitones &&
+           a.keyTrack == b.keyTrack &&
+           a.lengthFraction == b.lengthFraction &&
+           a.splineActive == b.splineActive;
+}
+
 double liveRampStep(double sampleRate) {
     if (!(sampleRate > 0.0)) return 0.0;  // also catches NaN
     return 1.0 / (kLiveRampSeconds * sampleRate);