S-VIEW-9: velocity->amp transfer curve (pure velocity_curve module + zones-payload v7 + Voice::start apply)

Default flat y=1 (R10-F1 Option A) replaces the linear velocity/127 at note-on — a deliberate, non-back-compat behavior change; v1-v6 blobs lift to the flat default.

tests/test_sample_map.cpp

@@ -1370,6 +1370,104 @@ static void testKeyTrackV5BackCompatLiftsToUnity() {
     CHECK(back.zones[0].keyTrack == 1.0);  // no keyTrack tail -> default 1.0 (bit-identical repitch)
 }
 
+// --- S-VIEW-9 velocity->amp curve: v7 round-trip + resolve-through + v6 back-compat lift ---------
+
+static void testVelocityCurveRoundTrip() {
+    // A per-zone velocity curve survives the payload-v7 round trip losslessly (exact point coords).
+    // A second zone left at the flat default proves the field is per-record and defaults to flat y=1.
+    PerformanceMap m;
+    PerformanceZone z = zone("lead", 20, 100);
+    z.velocityCurve = vst::VelocityCurve::linear();
+    z.velocityCurve.addPoint(60.0, 0.3);   // an interior knot to exercise multi-point round-trip
+    m.zones.push_back(z);
+    m.zones.push_back(zone("pad", 0, 19));  // default flat curve
+    const PerformanceMap back = deserializePerformance(serializePerformance(m), 44100.0);
+    CHECK(back.zones.size() == 2);
+    if (back.zones.size() != 2) return;
+    CHECK(back.zones[0].velocityCurve.equals(z.velocityCurve));       // exact point round-trip
+    CHECK(back.zones[1].velocityCurve.equals(vst::VelocityCurve::flat()));  // default preserved
+    // And the flat default really is unity everywhere (R10-F1 Option A), not the old linear ramp.
+    CHECK(back.zones[1].velocityCurve.eval(1.0) == 1.0);
+    CHECK(back.zones[1].velocityCurve.eval(64.0) == 1.0);
+}
+
+static void testVelocityCurveThroughComponentEnvelope() {
+    // The curve round-trips through the ComponentState envelope too (zones-payload is envelope-
+    // independent, so it carries the v7 tail unchanged).
+    ComponentState s;
+    s.selectionId = "pick";
+    PerformanceZone z = zone("pick", 0, 127);
+    z.velocityCurve = vst::VelocityCurve::linear();
+    s.map.zones.push_back(z);
+    const ComponentState back = deserializeComponentState(serializeComponentState(s), 44100.0);
+    CHECK(back.map.zones.size() == 1);
+    if (back.map.zones.size() != 1) return;
+    CHECK(back.map.zones[0].velocityCurve.equals(vst::VelocityCurve::linear()));
+}
+
+static void testVelocityCurveResolvesToZone() {
+    // resolvePerformance carries the curve from PerformanceZone through to ResolvedZone, so the
+    // keymap build (and thus the voice engine at start()) sees the authored curve.
+    const std::string json = bookJson({makeSample("a", "Kick", "b/a.wav", 36)}, {});
+    PerformanceMap m;
+    PerformanceZone z = zone("a", 0, 127);
+    z.velocityCurve = vst::VelocityCurve::linear();
+    m.zones.push_back(z);
+    const ResolvedPerformance r = resolvePerformance(json, m);
+    CHECK(r.zones.size() == 1);
+    if (r.zones.size() != 1) return;
+    CHECK(r.zones[0].velocityCurve.equals(vst::VelocityCurve::linear()));
+}
+
+static void testVelocityCurveV6BackCompatLiftsToFlat() {
+    // A v6 PAYLOAD blob (marker + version 6 + full play tail + keyTrack, but NO velocity-curve field)
+    // lifts every zone to VelocityCurve::flat() (R10-F1 Option A — flat y=1). This is the DELIBERATE
+    // non-back-compat behavior change: an instance saved BEFORE S-VIEW-9 now plays every velocity at
+    // unity, NOT the old linear velocity/127. Hand-build the exact v6 record shape.
+    std::vector<std::uint8_t> b;
+    auto u32 = [&](std::uint32_t v) {
+        b.push_back(v & 0xFF); b.push_back((v >> 8) & 0xFF);
+        b.push_back((v >> 16) & 0xFF); b.push_back((v >> 24) & 0xFF);
+    };
+    auto f64 = [&](double d) {
+        std::uint64_t bits; std::memcpy(&bits, &d, sizeof(bits));
+        for (int i = 0; i < 8; ++i) b.push_back(static_cast<std::uint8_t>((bits >> (i * 8)) & 0xFF));
+    };
+    auto i64 = [&](std::int64_t v) {
+        std::uint64_t bits = static_cast<std::uint64_t>(v);
+        for (int i = 0; i < 8; ++i) b.push_back(static_cast<std::uint8_t>((bits >> (i * 8)) & 0xFF));
+    };
+    u32(kPerformanceStateVersion);   // envelope version (2)
+    u32(kZonesFormatMarker);         // marker -> a versioned payload
+    u32(6);                          // PAYLOAD VERSION 6 (pre-S-VIEW-9, keyTrack but no curve)
+    u32(1);                          // zone count 1
+    const std::string id = "v6saved";
+    u32(static_cast<std::uint32_t>(id.size()));
+    b.insert(b.end(), id.begin(), id.end());
+    u32(10); u32(70);                // low/high
+    b.push_back(0);                  // hasRootOverride = 0
+    b.push_back(0);                  // hasLoopOverride = 0
+    b.push_back(0);                  // hasStartPoint = 0
+    // v5 play tail.
+    b.push_back(0);                  // playMode = Gate
+    f64(0.0);                        // adsr.holdSeconds
+    f64(1.0);                        // trigger.lengthFraction
+    i64(0); i64(0);                  // trigger fades
+    b.push_back(1);                  // pitchEngine = Preserve
+    b.push_back(0);                  // pitchEnv.enabled = false
+    f64(0.0); f64(0.0); f64(0.0);    // pitchEnv attack/decay/peak
+    f64(0.003); f64(0.0); f64(1.0); f64(0.060);  // adsr A/D/S/R
+    f64(0.5);                        // v6 keyTrack (0.5) — present, but no curve tail follows
+    const PerformanceMap back = deserializePerformance(b, 44100.0);
+    CHECK(back.zones.size() == 1);
+    if (back.zones.size() != 1) return;
+    CHECK(back.zones[0].sampleId == "v6saved");
+    CHECK(back.zones[0].keyTrack == 0.5);  // the v6 field still read correctly
+    // No curve tail -> flat y=1 default (the deliberate behavior change).
+    CHECK(back.zones[0].velocityCurve.equals(vst::VelocityCurve::flat()));
+    CHECK(back.zones[0].velocityCurve.eval(20.0) == 1.0);  // a soft hit now plays at unity
+}
+
 static void testPlayParamsV2BackCompatLiftsToDefaults() {
     // A pre-S15 PAYLOAD v2 blob (marker + version 2 + record with the S11 tail but NO play tail)
     // lifts each zone to the PRODUCT defaults: Gate + Preserve (S16-F1) + no fades + env off — the
@@ -1619,6 +1717,10 @@ int main() {
     testKeyTrackThroughComponentEnvelope();
     testKeyTrackResolvesToZone();
     testKeyTrackV5BackCompatLiftsToUnity();
+    testVelocityCurveRoundTrip();
+    testVelocityCurveThroughComponentEnvelope();
+    testVelocityCurveResolvesToZone();
+    testVelocityCurveV6BackCompatLiftsToFlat();
     testPlayParamsV2BackCompatLiftsToDefaults();
     testPlayParamsThroughComponentEnvelope();
     testFullAdsrSecondsRoundTrip();