fix: restore waveform symmetry about the midline, cut deck_values' link to the bank model, and unit-test the column arithmetic

The waveform column's vertical extents move to pure component_geometry so the shared
primitive stops being untested; PlaySeconds hoists into a header-only play_seconds target.

src/core/instrument/CLAUDE.md

@@ -291,6 +291,7 @@ anything for a trigger shape.
 ### `map/`
 
 - `sample_map` — the bank blob → selected capture resolve, the channel policy (downmix / dual-mono / L-R split), `InstrumentParams` (the ONE parameter set: root/loop/start overrides, keyTrack, velocity curve, `PlaySeconds`), the single override-beats-intrinsic fold (`resolveCapture`, shared by the bank and refs paths so they cannot drift), and the `SampleData` build. **Wall-clock times stored as rate-free SECONDS, resolved against the live project rate — NO hardcoded sample rates in `src/`** (Daniel's standing ruling, load-bearing). Deliberately does NOT link the voice engine: the build's product is plain `SampleData`.
+- `play_seconds` — the stored, wall-clock-SECONDS value layer (`PlaySeconds` + `AdsrSeconds` / `AhdSeconds` / `PitchEnvSeconds` / `FilterSeconds`), header-only and split from `sample_map` so a consumer that only edits those values reaches them without the bank model and the WAV codec. `resolvePlay`, which turns them into the engine's frame domain, stays with the rest of the mapping.
 - `component_state_io` (`core/instrument/map`) — the `ComponentState` envelope + params-payload binary codec (envelope v1…v11, params payload v1…v13), split out of `sample_map` (Q-W2v, T4-13 ≡ T2-07) so BOTH artifacts can link the codec without the extension pulling in the whole voice engine to serialize one preset blob — the extension's `instrument_drop` and the instrument's processor read/write the identical bytes, so the cross-artifact contract cannot drift. Payload v1…v7 are the RETIRED per-zone lists: still read, lifting by adopting zone one's capture + parameters (that first zone is what the old first-match resolve actually played, so it is also what supersedes the envelope's stored selection id). Payload v9 appends the per-voice filter tail; a v8 blob is a strict prefix of it and lifts to the off/neutral filter default. Every tail since is a strict suffix on the same discipline — v10 the staged curves, v11 the loop crossfade, v12 the velocity→pitch curve, v13 the dual Staged/Spline state (the three contours, plus hard-flag tails for the three velocity curves — their v7/v9/v12 blocks are frozen at 16 bytes/point and had no room for a per-point flag). v12 also RE-TAGS the y DOMAIN of one frozen slot inside the v9 filter tail — its velocity curve reads bipolar from v12 on, unipolar before — which needs no version branch, because a pre-v12 curve's y values are already valid bipolar ones; every other filter slot, `velAmount` included, keeps its meaning.
 - `params_payload` — the PARAMS-PAYLOAD half of that codec, split from the envelope half on the axis the format already has: the payload carries its own version and grows independently, so the two version ladders are two responsibilities. An INTERNAL seam — the public entry points stay `serialize`/`deserializeComponentState`. The prose ladder and every version constant stay in `component_state_io.h`, their one home.
 - `bank_sync` — generation change-detection + assignment-request consume: owns the yes/no decision logic so the rules are provable without a host. The processor shell owns cadence and side effects.
@@ -318,9 +319,11 @@ anything for a trigger shape.
   `PlaySeconds`, so there is no second table of defaults to drift), and `formatEnvTimeMs`, the
   ONE time-constant formatter: every displayed time constant reads in **ms**, never seconds, so
   two stage times are comparable at a glance. A display-unit decision only — nothing about the
-  stored representation changes. Links the map layer because `PlaySeconds` is what a deck edits.
-  The shell keeps only the controls the parameter set does not carry (key-track, voice count,
-  master gain, preview velocity) and the labels for them.
+  stored representation changes. Links the header-only `play_seconds`, deliberately not
+  `sample_map`: `PlaySeconds` is the whole of what a deck edits, and linking the mapping would
+  drag the bank model and the WAV codec in behind it. The shell keeps only the controls the
+  parameter set does not carry (key-track, voice count, master gain, preview velocity) and the
+  labels for them.
 - `deck_groups` — also home to `isLiveDeckParam` and `liveCommitFor`, the editor's whole commit-tier routing decision (see "Live parameter delivery" above), and to `OverlayEnv` + `nextOverlaySelection`/`overlayEnvEnabled`/`overlayEnvInert`, the whole overlay-selection state machine (exclusivity, the none resting state, and which selections a disabled or DRAWN group makes inert); WHICH groups the Sample face's deck carries, split from `knob_deck`'s HOW they lay out: the `DeckParam` control-id space (the editor's `ParamControl` is an alias of it), the `DeckGroupId` list, `sampleDeckGroups` in signal-flow order (**pitch → filter → amp**, then velocity/voice/master), and the deck's bipolar-knob law. Reads `PlayMode` for the AMP group's Gate/Trigger face, which is why this and not `knob_deck` is the module that touches the engine's value layer. Also home to `CurveTarget` + `curveTargetFor` — the VELOCITY group's three cells are popup openers, not dials, and that predicate is the ONE place they are named, so paint, hit-test routing and the popup's title all agree. MASTER is reserved for post-voice-mixer concerns, which is why the curves sit in their own group immediately left of VOICE rather than there.
 - `spline_edit` — THE point-editing grammar, and the one place it is written down: left-click grabs a node and adds one in empty space, right-click deletes, control-click toggles hard/smooth. Both spline consumers — the velocity-curve popup and the spline EG overlay — route their mouse-down through `resolveSplineEdit`, so the two cannot drift into two grammars. The endpoint and point-count rules are NOT restated here: `deletePoint` and `addPoint` own them, and the caller applies the resolved action to the curve. Also home to `splineOverlayBox`, the contour's mapping box inside the waveform overlay — the FULL area, no inset, so the drawn contour stays 1:1 with the sample's time axis.
 - `curve_popup` — pure curve-popup geometry + dismissal test (FB1): centered sheet over the Sample face — width/height clamps, title row, Close button rect, curve-box rect, outside-sheet dismissal test. Mirror of `overflow_menu`; no LICE or REAPER types.

src/core/instrument/map/CMakeLists.txt

@@ -26,10 +26,20 @@ reasampler_pure_library(component_state_io
 # proof the codec is engine-free, which is what keeps engine object code out of the extension.
 reasampler_test(component_state_io LINK component_state_io)
 
+# The stored seconds value layer, header-only (hence INTERFACE) — PlaySeconds and the four
+# stage-time structs it composes. Split from sample_map so a consumer that only edits those
+# values reaches them WITHOUT the bank model and the WAV codec: the editor's deck_values
+# binding is exactly that consumer, and linking sample_map for one value struct would put
+# bank_book + wav_codec into a test whose subject is a knob. Links the same value-layer set
+# play_params.h needs (velocity_curve's out-of-line zero() is a default member initializer).
+add_library(play_seconds INTERFACE)
+target_include_directories(play_seconds INTERFACE ${REASAMPLER_SRC_DIR})
+target_link_libraries(play_seconds INTERFACE velocity_curve peaks curve_law)
+
 # The mapping's product is plain SampleData, so the voice engine is not a dependency.
 reasampler_pure_library(sample_map
     SOURCES sample_map.cpp
-    LINK PUBLIC bank_book wav_codec velocity_curve peaks curve_law)
+    LINK PUBLIC bank_book wav_codec play_seconds velocity_curve peaks curve_law)
 # Links only sample_map + component_state_io: the same plain-data-boundary proof, spanning
 # both halves of the mapping/codec split where the frozen-format assertions live.
 reasampler_test(sample_map LINK sample_map component_state_io)

src/core/instrument/map/play_seconds.h

@@ -0,0 +1,88 @@
+#pragma once
+// play_seconds — the STORED, wall-clock-SECONDS value layer the instrument edits and
+// serializes: PlaySeconds and the four stage-time structs it composes. Header-only, and split
+// from sample_map so a consumer that only edits these values (the editor's deck binding) does
+// not link the bank model and the WAV codec to reach one value struct. `resolvePlay`, which
+// turns them into the engine's frame domain, stays in sample_map with the rest of the mapping.
+
+#include "core/instrument/engine/play_params.h"  // PlayMode / TriggerParams / SplineEnv / …
+
+namespace reasampler::instrument::map {
+
+using instrument::engine::VelocityCurve;
+
+// Daniel's standing ruling: no hardcoded sample rate anywhere in the program. The
+// instrument stores/edits wall-clock performance times (AHDSR A/H/D/R, pitch-env A/D) as
+// SECONDS, rate-free; the engine receives FRAMES resolved from the LIVE sample rate at
+// build. Quantities anchored to the source file's timeline (start point, loop points,
+// Trigger %-length + fades) stay in source frames/fractions, carried through unchanged
+// (TriggerParams reused verbatim).
+//
+// The stored AHDSR times (seconds). sustainLevel is dimensionless (0..1), not a time; the
+// three curve exponents are dimensionless too (curve_law.h owns their domain).
+struct AdsrSeconds {
+    double attackSeconds  = 0.003;  // tier-0 default
+    double holdSeconds    = 0.0;
+    double decaySeconds   = 0.0;
+    double sustainLevel   = 1.0;
+    double releaseSeconds = 0.060;  // tier-0 default
+    double attackCurve    = util::kCurveNeutral;
+    double decayCurve     = util::kCurveNeutral;
+    double releaseCurve   = util::kCurveNeutral;
+};
+
+// The stored sustain-less AHD: wall-clock stage times in SECONDS, Hold as a FRACTION of the
+// span left after them (AhdParams owns why a fraction, not a time).
+struct AhdSeconds {
+    double attackSeconds = 0.0;
+    double decaySeconds  = 0.0;
+    double holdFraction  = 1.0;
+    double attackCurve   = util::kCurveNeutral;
+    double decayCurve    = util::kCurveNeutral;
+};
+
+// The stored AHD pitch envelope. enabled + peakSemitones are dimensionless. The hold fraction
+// defaults to 0 so an instance predating the stage plays as its attack-decay predecessor did.
+struct PitchEnvSeconds {
+    bool       enabled       = false;
+    double     peakSemitones = 0.0;  // signed depth at the peak
+    AhdSeconds shape{0.0, 0.0, /*holdFraction=*/0.0, util::kCurveNeutral, util::kCurveNeutral};
+};
+
+// The stored mirror of the engine's FilterParams (play_params.h, which owns what each field
+// MEANS). Only the envelope differs between the two: the control positions and depths are
+// rate-free already, so this block is a seconds/frames split of one field, not of the whole
+// struct. The env default is a flat unity, so `enabled` is the only thing standing between a
+// loaded blob and the pre-filter sound.
+struct FilterSeconds {
+    bool enabled = false;
+    engine::filter::FilterSettings settings;
+    double modAmount = 0.0;
+    double velAmount = 0.0;
+    double keyTrack  = 0.0;
+    AdsrSeconds env{0.0, 0.0, 0.0, 1.0, 0.0};  // Gate
+    AhdSeconds  trigEnv;                       // Trigger
+    VelocityCurve velocityCurve = VelocityCurve::zero();
+};
+
+// The stored play bundle: wall-clock times in SECONDS, source-timeline quantities in
+// frames/fractions (TriggerParams). Instrument-owned, serialized, editor-facing — distinct
+// from the engine-facing PlayParams (frames).
+struct PlaySeconds {
+    PlayMode        playMode = PlayMode::Gate;
+    AdsrSeconds     adsr;                                 // Gate amp: AHDSR (seconds)
+    TriggerParams   trigger;                              // Trigger play span (%-length)
+    AhdSeconds      trigAhd;                              // Trigger amp: AHD (seconds + fraction)
+    PitchEngine     pitchEngine = kDefaultPitchEngine;    // product default: Preserve
+    PitchEnvSeconds pitchEnv;                             // AHD pitch modulation, off by default
+    VelocityCurve   pitchVelocityCurve = VelocityCurve::zero();  // velocity -> pitch, off by default
+    FilterSeconds   filter;                               // per-voice filter, off by default
+    // The three drawn contours, in the same slots the engine bundle carries them (play_params.h
+    // owns why they sit beside the envelopes rather than inside them). Normalized over the
+    // sample's own length, so resolvePlay needs no rate for them.
+    SplineEnv       ampSpline;
+    SplineEnv       pitchSpline;
+    SplineEnv       filterSpline;
+};
+
+}  // namespace reasampler::instrument::map

src/core/instrument/map/sample_map.h

@@ -14,6 +14,7 @@
 
 #include "core/model/bank_book.h"       // BankBook::deserialize (shared bank JSON parse)
 #include "core/instrument/engine/play_params.h"  // SampleData, SampleLoop, PlayParams
+#include "core/instrument/map/play_seconds.h"    // PlaySeconds (the stored seconds value layer)
 #include "core/capture/wav_codec.h"        // parseWavLayout, extractFloatFrames (shared WAV parse)
 
 namespace reasampler::instrument::map {
@@ -134,81 +135,7 @@ std::vector<AudioSample> downmixToMono(const std::vector<AudioSample>& interleav
 std::vector<AudioSample> extractChannel(const std::vector<AudioSample>& interleaved,
                                         int channelCount, int which);
 
-// --- Stored (wall-clock SECONDS) play params ----------------------------------
-//
-// Daniel's standing ruling: no hardcoded sample rate anywhere in the program. The
-// instrument stores/edits wall-clock performance times (AHDSR A/H/D/R, pitch-env A/D) as
-// SECONDS, rate-free; the engine receives FRAMES resolved from the LIVE sample rate at
-// build. Quantities anchored to the source file's timeline (start point, loop points,
-// Trigger %-length + fades) stay in source frames/fractions, carried through unchanged
-// (TriggerParams reused verbatim).
-//
-// The stored AHDSR times (seconds). sustainLevel is dimensionless (0..1), not a time; the
-// three curve exponents are dimensionless too (curve_law.h owns their domain).
-struct AdsrSeconds {
-    double attackSeconds  = 0.003;  // tier-0 default
-    double holdSeconds    = 0.0;
-    double decaySeconds   = 0.0;
-    double sustainLevel   = 1.0;
-    double releaseSeconds = 0.060;  // tier-0 default
-    double attackCurve    = util::kCurveNeutral;
-    double decayCurve     = util::kCurveNeutral;
-    double releaseCurve   = util::kCurveNeutral;
-};
-
-// The stored sustain-less AHD: wall-clock stage times in SECONDS, Hold as a FRACTION of the
-// span left after them (AhdParams owns why a fraction, not a time).
-struct AhdSeconds {
-    double attackSeconds = 0.0;
-    double decaySeconds  = 0.0;
-    double holdFraction  = 1.0;
-    double attackCurve   = util::kCurveNeutral;
-    double decayCurve    = util::kCurveNeutral;
-};
-
-// The stored AHD pitch envelope. enabled + peakSemitones are dimensionless. The hold fraction
-// defaults to 0 so an instance predating the stage plays as its attack-decay predecessor did.
-struct PitchEnvSeconds {
-    bool       enabled       = false;
-    double     peakSemitones = 0.0;  // signed depth at the peak
-    AhdSeconds shape{0.0, 0.0, /*holdFraction=*/0.0, util::kCurveNeutral, util::kCurveNeutral};
-};
-
-// The stored mirror of the engine's FilterParams (play_params.h, which owns what each field
-// MEANS). Only the envelope differs between the two: the control positions and depths are
-// rate-free already, so this block is a seconds/frames split of one field, not of the whole
-// struct. The env default is a flat unity, so `enabled` is the only thing standing between a
-// loaded blob and the pre-filter sound.
-struct FilterSeconds {
-    bool enabled = false;
-    engine::filter::FilterSettings settings;
-    double modAmount = 0.0;
-    double velAmount = 0.0;
-    double keyTrack  = 0.0;
-    AdsrSeconds env{0.0, 0.0, 0.0, 1.0, 0.0};  // Gate
-    AhdSeconds  trigEnv;                       // Trigger
-    VelocityCurve velocityCurve = VelocityCurve::zero();
-};
-
-// The stored play bundle: wall-clock times in SECONDS, source-timeline quantities in
-// frames/fractions (TriggerParams). Instrument-owned, serialized, editor-facing — distinct
-// from the engine-facing PlayParams (frames).
-struct PlaySeconds {
-    PlayMode        playMode = PlayMode::Gate;
-    AdsrSeconds     adsr;                                 // Gate amp: AHDSR (seconds)
-    TriggerParams   trigger;                              // Trigger play span (%-length)
-    AhdSeconds      trigAhd;                              // Trigger amp: AHD (seconds + fraction)
-    PitchEngine     pitchEngine = kDefaultPitchEngine;    // product default: Preserve
-    PitchEnvSeconds pitchEnv;                             // AHD pitch modulation, off by default
-    VelocityCurve   pitchVelocityCurve = VelocityCurve::zero();  // velocity -> pitch, off by default
-    FilterSeconds   filter;                               // per-voice filter, off by default
-    // The three drawn contours, in the same slots the engine bundle carries them (play_params.h
-    // owns why they sit beside the envelopes rather than inside them). Normalized over the
-    // sample's own length, so resolvePlay needs no rate for them.
-    SplineEnv       ampSpline;
-    SplineEnv       pitchSpline;
-    SplineEnv       filterSpline;
-};
+// --- Seconds -> frames --------------------------------------------------------
 
 // Resolve a stored seconds bundle to the engine's frame-domain PlayParams against a live
 // sample rate (frames = round(seconds * rate)). Source-timeline fields carry through

src/core/instrument/ui/CMakeLists.txt

@@ -7,7 +7,9 @@ reasampler_pure_library(sample_bands SOURCES sample_bands.cpp LINK PUBLIC editor
 reasampler_test(sample_bands LINK sample_bands)
 
 reasampler_pure_library(sample_chrome SOURCES sample_chrome.cpp LINK PUBLIC sample_bands)
-reasampler_test(sample_chrome LINK sample_chrome)
+# knob_deck is linked for the test only: the knob size the shell hands chromeRects is
+# kDeckKnobSize, and the test reads the real constant rather than copying its value.
+reasampler_test(sample_chrome LINK sample_chrome knob_deck)
 
 reasampler_pure_library(embed_strip SOURCES embed_strip.cpp LINK PUBLIC editor_geometry)
 reasampler_test(embed_strip LINK embed_strip)
@@ -69,12 +71,12 @@ reasampler_pure_library(spline_edit
 reasampler_test(spline_edit LINK spline_edit waveform_view sample_bands)
 
 # The deck's VALUE binding, split from its composition on the same axis deck_groups was split
-# from knob_deck. Links sample_map because PlaySeconds — the thing a deck knob edits — is
-# declared there; no sample_map symbol is called, only its value types. Same for the filter's
-# MorphLaw — an enum, so no filter symbol is linked.
+# from knob_deck. Links the header-only play_seconds, NOT sample_map: PlaySeconds is all a deck
+# knob edits, and sample_map would drag the bank model and the WAV codec in behind it. Same for
+# the filter's MorphLaw — an enum, so no filter symbol is linked.
 reasampler_pure_library(deck_values
     SOURCES deck_values.cpp
-    LINK PUBLIC deck_groups sample_map envelope_overlay)
+    LINK PUBLIC deck_groups play_seconds envelope_overlay)
 reasampler_test(deck_values LINK deck_values)
 
 reasampler_pure_library(curve_popup SOURCES curve_popup.cpp LINK PUBLIC editor_geometry)

src/core/instrument/ui/deck_values.h

@@ -2,13 +2,13 @@
 // normalized 0..1 a knob shows, the write back into the stored seconds/fractions/positions, the
 // double-click reset, and the ms time-constant formatter. Split from the editor shell so the
 // whole domain map is provable without a host; deck_groups owns WHICH controls exist, this owns
-// what each one's value MEANS. Links the map layer because PlaySeconds is what a deck edits.
+// what each one's value MEANS.
 
 #pragma once
 
 #include <cstddef>
 
-#include "core/instrument/map/sample_map.h"        // PlaySeconds (the deck's edit target)
+#include "core/instrument/map/play_seconds.h"      // PlaySeconds (the deck's edit target)
 #include "core/instrument/ui/deck_groups.h"        // DeckParam
 #include "core/instrument/ui/envelope_overlay.h"   // kGateStageMaxSeconds
 
@@ -39,9 +39,11 @@ double deckParamNorm(DeckParam id, const PlaySeconds& play);
 void setDeckParam(DeckParam id, PlaySeconds& play, double value, int segment);
 
 // Resets `id` to its default. The default IS what a fresh PlaySeconds carries, so there is no
-// second table of defaults to drift from the real one. Exact for every shipped default: they
-// are all 0, 1, or the curve neutral, and the seconds ceiling is a power of two, so the
-// norm round trip loses nothing. For knob-valued controls — a toggle has no reset gesture.
+// second table of defaults to drift from the real one. It arrives via the norm round trip, so
+// landing EXACTLY on a stage time (0.003 s attack, 0.060 s release) depends on
+// kEnvTimeMaxSeconds being a power of two — x/2^n*2^n is lossless, an arbitrary ceiling is not.
+// Move that ceiling off a power of two and a reset lands a mantissa bit off its own default.
+// For knob-valued controls — a toggle has no reset gesture.
 void resetDeckParam(DeckParam id, PlaySeconds& play);
 
 // A time constant as MILLISECONDS, e.g. "12 ms". Never switches to seconds: the editor reads in

src/core/instrument/ui/knob_deck.cpp

@@ -190,24 +190,19 @@ DeckHit hitTestDeck(const DeckLayout& layout, int x, int y) {
     return {};
 }
 
-namespace {
-// Squared distance from a rect's centre, in the rect's own pixel units.
-double distSqFromCentre(const Rect& r, int x, int y) {
-    const double dx = x - (r.x + r.width / 2.0);
-    const double dy = y - (r.y + r.height / 2.0);
-    return dx * dx + dy * dy;
+bool inKnobFace(const Rect& knob, int x, int y) {
+    const double dx = x - (knob.x + knob.width / 2.0);
+    const double dy = y - (knob.y + knob.height / 2.0);
+    const double r = knob.width / 2.0;
+    return dx * dx + dy * dy < r * r;
 }
-}  // namespace
 
 DeckFaceHit hitTestKnobFace(const DeckLayout& layout, int x, int y) {
     for (const DeckGroupLayout& g : layout.groups) {
         if (!contains(g.box, x, y)) continue;
         for (const DeckCellLayout& c : g.cells) {
-            const double rOuter = c.knob.width / 2.0;
-            if (distSqFromCentre(c.knob, x, y) >= rOuter * rOuter) continue;
-            const double rInner = c.inner.width / 2.0;
-            const bool inner = distSqFromCentre(c.inner, x, y) < rInner * rInner;
-            return {c.id, inner};
+            if (!inKnobFace(c.knob, x, y)) continue;
+            return {c.id, inKnobFace(c.inner, x, y)};
         }
         return {};  // inside the group but off every dial
     }

src/core/instrument/ui/knob_deck.h

@@ -153,11 +153,18 @@ struct DeckFaceHit {
     bool inner = false;  // inside the concentric inner disc
 };
 
+// A point inside the circle inscribed in `knob`, boundary-EXCLUSIVE. THE target rule for the
+// reset gesture wherever a radial knob is drawn — the deck's own faces and the chrome's
+// preview-velocity dial both resolve through it, so one gesture cannot grow two target rules.
+bool inKnobFace(const Rect& knob, int x, int y);
+
 // Resolved against the drawn CIRCLES, not the cell: a reset is aimed at a dial, so the label
-// band and the cell margins must miss where a drag grab deliberately does not. Both radii are
-// boundary-EXCLUSIVE, one rule for both rings — a point exactly on the inner radius is an
-// outer-ring hit, one exactly on the outer radius is a miss. Whether a cell actually carries an
-// inner value is deck_groups' call, exactly as with DeckHit::inner.
+// band and the cell margins must miss where a drag grab deliberately does not. One rule for
+// both rings — a point exactly on the inner radius is an outer-ring hit, one exactly on the
+// outer radius is a miss. Whether a cell actually carries an inner value is deck_groups' call,
+// exactly as with DeckHit::inner. Unlike hitTestDeck this runs NO toggle/radio precedence pass
+// first, which is only correct while no toggle rect overlaps a knob circle — a layout change
+// that lets them overlap has to give this the same precedence order.
 DeckFaceHit hitTestKnobFace(const DeckLayout& layout, int x, int y);
 
 }  // namespace reasampler::instrument::ui

src/core/ui/component_geometry.cpp

@@ -97,4 +97,31 @@ int waveformColumnCount(const KitBox& box) {
     return w > 0 ? w : 0;
 }
 
+WaveformBand waveformBand(int bandTop, int bandHeight) {
+    WaveformBand b;
+    b.top = bandTop;
+    b.height = bandHeight;
+    b.midY = bandTop + bandHeight / 2;
+    b.halfSpan = (bandHeight / 2) - 2;  // matches drawWaveform's 2px vertical breathing room
+    return b;
+}
+
+WaveformColumnSpan waveformColumnSpan(const WaveformBand& band,
+                                      double compressedMax, double compressedMin) {
+    const int lo = band.top;
+    const int hi = band.top + band.height - 1;
+
+    WaveformColumnSpan s;
+    s.top = band.midY - static_cast<int>(compressedMax * band.halfSpan);
+    s.bottom = band.midY - static_cast<int>(compressedMin * band.halfSpan);
+    s.topF = band.midY - compressedMax * band.halfSpan;
+    s.bottomF = band.midY - compressedMin * band.halfSpan;
+
+    if (s.top < lo) s.top = lo;
+    if (s.bottom > hi) s.bottom = hi;
+    if (s.topF < lo) s.topF = lo;
+    if (s.bottomF > hi) s.bottomF = hi;
+    return s;
+}
+
 } // namespace reasampler::ui

src/core/ui/component_geometry.h

@@ -75,11 +75,38 @@ ListRowBox computeListRow(const KitBox& list, int index, int rowHeight);
 // `rowCount` rows). rowCount bounds the hit so blank space past the last row is a clean miss.
 int hitTestListRow(int px, int py, const KitBox& list, int rowHeight, int rowCount);
 
-// --- Waveform column count ---------------------------------------------------
+// --- Waveform columns --------------------------------------------------------
 
 // Pixel columns drawWaveform renders inside `box` (its fixed 2px side insets), never negative.
 // Pass directly as peaks::computeEnvelope's binCount — one bin per column is correct resolution;
 // overbinning doesn't improve render quality and wastes memory/CPU.
 int waveformColumnCount(const KitBox& box);
 
+// One channel band's shared vertical metrics: the zero line every column mirrors about, and the
+// pixel height a full-scale amplitude reaches (inset so a peak keeps the band's breathing room).
+struct WaveformBand {
+    int    top      = 0;
+    int    height   = 0;
+    int    midY     = 0;
+    double halfSpan = 0.0;
+};
+WaveformBand waveformBand(int bandTop, int bandHeight);
+
+// The vertical extents of one column: the integer edges of the filled span, and the same edges
+// at sub-pixel precision for the antialiased outline stroke that joins a column's extremes to
+// its neighbour's. Both take the band clamp, so the stroke cannot leave the band the fill is
+// confined to. Amplitudes arrive already through the display curve.
+struct WaveformColumnSpan {
+    int    top     = 0;
+    int    bottom  = 0;
+    double topF    = 0.0;
+    double bottomF = 0.0;
+};
+
+// Truncation is applied to the SCALED AMPLITUDE and then mirrored about midY — never to the
+// resulting y, which would round the two edges in opposite directions and leave a column with
+// |max| == |min| a pixel taller above the zero line than below.
+WaveformColumnSpan waveformColumnSpan(const WaveformBand& band,
+                                      double compressedMax, double compressedMin);
+
 } // namespace reasampler::ui

src/shell/instrument/editor_input_chrome.cpp

@@ -7,6 +7,7 @@
 #ifdef _WIN32
 
 #include "core/instrument/ui/keyboard_strip.h"  // keyAtPoint / resolveDragNote (root key)
+#include "core/instrument/ui/knob_deck.h"       // inKnobFace (the shared reset target rule)
 #include "shell/instrument/editor_internal.h"
 #include "shell/instrument/reasampler_processor.h"
 
@@ -82,11 +83,10 @@ bool ReaSamplerEditor::mouseDownChrome(const FaceLayout& fl, int x, int y) {
 
 bool ReaSamplerEditor::doubleClickChrome(const FaceLayout& fl, int x, int y) {
     // The preview-velocity dial answers the same reset gesture the deck's knobs do — it is a
-    // radial knob drawn by the same primitive, so a user who learns the gesture there expects
-    // it here. Resolved against the whole cell, not the circle: the cell IS the knob's target
-    // on this surface (there is no neighbouring control to steal from).
+    // radial knob drawn by the same primitive, so it resolves through the same target rule
+    // (inKnobFace), against the drawn circle rather than the cell's label band.
     if (selectedId_.empty() || !processor_) return false;
-    if (!contains(fl.chrome.velCell, x, y)) return false;
+    if (!inKnobFace(fl.chrome.velKnob, x, y)) return false;
     processor_->setPreviewVelocity(kPreviewVelocityDefault);
     invalidate();
     return true;

src/shell/panel/CLAUDE.md

@@ -56,7 +56,7 @@ live in `shell/bank_ops`, a sibling directory, not here.
   - `panel_thumbnails` — the PCM→envelope thumbnail cache + the bank-change fingerprint pass.
   - `panel_audition` — the preview-playback engine.
   - `panel_bank_ops` — the menu/prompt UX skin over the promptless `shell/bank_ops` verbs.
-- `draw_kit` — shared LICE draw shell: `fillSurface`, `drawButton`/`drawSlider`/`drawListRow`/`drawWaveform`, cached-font `text()`, full interaction-state model, double-buffer preserved. Consumes `theme` + `component_geometry`.
+- `draw_kit` — shared LICE draw shell: `fillSurface`, `drawButton`/`drawSlider`/`drawListRow`/`drawWaveform`, cached-font `text()`, full interaction-state model, double-buffer preserved. Consumes `theme` + `component_geometry`. Its antialiasing contract — which surfaces alias, which cannot, and the LICE primitive each answers with — is the disposition table in `docs/product/visual-design-language.md` §8, which governs `drawWaveform` as much as this doc does. `drawWaveform`'s per-column vertical arithmetic is NOT here: it is the pure, unit-tested `component_geometry::waveformBand`/`waveformColumnSpan` pair, because this TU is DAW-verified and not unit-tested.
 
 ## Gotchas
 

src/shell/panel/draw_kit.cpp

@@ -27,6 +27,10 @@ using ui::compressAmplitudeForDisplay;
 using ui::roleColor;
 using ui::roleColorState;
 using ui::spectralColor;
+using ui::WaveformBand;
+using ui::waveformBand;
+using ui::WaveformColumnSpan;
+using ui::waveformColumnSpan;
 
 // The one place a pure KitColor becomes a LICE_pixel (LICE_RGBA(r,g,b,a), verified against
 // lice.h). The theme owns the color; the shell owns the packing.
@@ -289,11 +293,9 @@ void drawWaveform(LICE_IBitmap* bmp, const KitBox& box, const Envelope& env) {
 
     for (int ch = 0; ch < channels; ++ch) {
         const ChannelEnvelope& bins = env[static_cast<std::size_t>(ch)];
-        const int bandTop = box.y + ch * bandH;
-        const int midY = bandTop + bandH / 2;
-        const double halfSpan = (bandH / 2) - 2;
+        const WaveformBand band = waveformBand(box.y + ch * bandH, bandH);
 
-        LICE_Line(bmp, box.x + 2, midY, box.x + box.width - 2, midY,
+        LICE_Line(bmp, box.x + 2, band.midY, box.x + box.width - 2, band.midY,
                   midCol, 1.0f, 0, false);
 
         if (bins.empty() || innerW <= 0) continue;
@@ -303,28 +305,22 @@ void drawWaveform(LICE_IBitmap* bmp, const KitBox& box, const Envelope& env) {
         // alone leaves the outline stepped — a vertical span has no aa to apply — and where two
         // adjacent columns differ sharply it reads as a comb rather than one envelope. The
         // stroke is the SAME ink as the fill it edges, so it can only soften the boundary.
-        double prevTop = 0.0;
-        double prevBottom = 0.0;
+        WaveformColumnSpan prev;
         for (int col = 0; col < innerW; ++col) {
             const MinMax mm = columnMinMax(bins, innerW, col);
             const int x = box.x + 2 + col;
-            const double topF = midY - compressAmplitudeForDisplay(mm.max) * halfSpan;
-            const double bottomF = midY - compressAmplitudeForDisplay(mm.min) * halfSpan;
-            int yMax = static_cast<int>(topF);
-            int yMin = static_cast<int>(bottomF);
-            if (yMax < bandTop) yMax = bandTop;
-            if (yMin > bandTop + bandH - 1) yMin = bandTop + bandH - 1;
-            LICE_Line(bmp, x, yMin, x, yMax, waveCol, 1.0f, 0, false);
+            const WaveformColumnSpan s = waveformColumnSpan(
+                band, compressAmplitudeForDisplay(mm.max), compressAmplitudeForDisplay(mm.min));
+            LICE_Line(bmp, x, s.bottom, x, s.top, waveCol, 1.0f, 0, false);
             if (col > 0) {
                 const float xPrev = static_cast<float>(x - 1);
                 const float xF = static_cast<float>(x);
-                LICE_FLine(bmp, xPrev, static_cast<float>(prevTop), xF,
-                           static_cast<float>(topF), waveCol, 1.0f, 0, true);
-                LICE_FLine(bmp, xPrev, static_cast<float>(prevBottom), xF,
-                           static_cast<float>(bottomF), waveCol, 1.0f, 0, true);
+                LICE_FLine(bmp, xPrev, static_cast<float>(prev.topF), xF,
+                           static_cast<float>(s.topF), waveCol, 1.0f, 0, true);
+                LICE_FLine(bmp, xPrev, static_cast<float>(prev.bottomF), xF,
+                           static_cast<float>(s.bottomF), waveCol, 1.0f, 0, true);
             }
-            prevTop = topF;
-            prevBottom = bottomF;
+            prev = s;
         }
     }
 }