Fix stale hover latch on drag release, tooltip anchor, border off-by-one; pin gutter golden test, drop DPI framing

src/core/instrument/CLAUDE.md

@@ -242,3 +242,8 @@ slider couldn't. Two pure modules split the forward (draw) and inverse (edit) ma
   Channel-mode (D-E) bus-renegotiation design and the earlier Preserve-onset-latency
   framing in the S16 guardrails. Root `CLAUDE.md` is the current source of truth
   for both — do not reintroduce either superseded design.
+- **`keyboard_strip`'s width-uniformity guarantee is client-pixel only.** Its test sweep
+  covers client-pixel widths (including multiples standing in for larger client areas);
+  nothing in the instrument implements `IPlugViewContentScaleSupport`, so host-side DPI
+  scaling of the plugin window — which would resample the uniform integer key widths at the
+  physical-pixel level — is unverified.

src/core/instrument/ui/keyboard_strip.h

@@ -1,9 +1,7 @@
 // keyboard_strip.h — piano-keyboard geometry for the editor's root strip: per-class key
 // rects, hit-test, the root marker, and the note name a hovered key reports.
 //
-// Same-class keys are one integer width by construction. An arbitrary band width is not
-// divisible by the 75 white keys, so the residue lands in symmetric end margins — uniform
-// key widths and gap-free edge-to-edge tiling cannot both hold, and uniformity wins.
+// See src/core/instrument/CLAUDE.md for the uniform-width-vs-edge-to-edge-tiling tradeoff.
 
 #pragma once
 
@@ -21,7 +19,8 @@ inline constexpr int kStripKeyCount = 128;
 inline constexpr int kStripWhiteKeyCount = 75;
 
 struct StripLayout {
-    Rect band;   // the surface handed in, edge to edge
+    Rect band;   // the surface handed in, edge to edge (no src/ consumer; kept as the tests'
+                 // reference bound instead of recomputing Rect::ltrb(0, 0, w, h) at each call site)
     Rect keys;   // the tiled key area, kStripWhiteKeyCount * whiteWidth, centred in band
     int whiteWidth = 0;
     int blackWidth = 0;

src/core/instrument/ui/sample_chrome.cpp

@@ -4,7 +4,7 @@
 
 #include <algorithm>
 
-#include "core/instrument/ui/sample_bands.h"  // kPad / kTitleHeight / kChromeRowHeight
+#include "core/instrument/ui/sample_bands.h"  // kPad
 
 namespace reasampler::instrument::ui {
 

src/shell/instrument/editor_input.cpp

@@ -79,6 +79,11 @@ void ReaSamplerEditor::onMouseUp(int x, int y) {
     drag_ = DragKind::kNone;
     dragParamId_ = -1;
     curvePointIndex_ = -1;
+    // hover_ is deliberately not re-resolved during a drag (see resolveHover's caller), so it
+    // still names wherever the drag started. Re-resolve now against the release position, for
+    // every drag kind — otherwise the next paint latches a stale hover (wrong note name/tooltip,
+    // wrong control outline) until the next WM_MOUSEMOVE.
+    resolveHover(x, y);
     // A scrollbar drag is transient UI (no parameter change), and the processor-side knobs
     // (the preview-velocity -2 sentinel, voice count, master gain) are per-instance settings
     // that don't reload the instrument. Master gain is an atomic the audio thread reads

src/shell/instrument/editor_input_chrome.cpp

@@ -75,7 +75,6 @@ bool ReaSamplerEditor::mouseDownChrome(const FaceLayout& fl, int x, int y) {
         const StripLayout sl = layoutStrip(cr.rootStrip.width, cr.rootStrip.height);
         if (keyAtPoint(sl, x - cr.rootStrip.x, y - cr.rootStrip.y) >= 0) {
             drag_ = DragKind::kRootMarker;
-            dragStartX_ = x;
             dragStartParams_ = params_;
             onMouseMove(x, y);
             return true;

src/shell/instrument/editor_paint_chrome.cpp

@@ -205,13 +205,16 @@ void ReaSamplerEditor::paintChromeTooltip(LICE_IBitmap* bmp, const FaceLayout& f
 
     const std::string label = noteName(hover_.index);
     const int textW = static_cast<int>(label.size()) * kTooltipCharPx;
-    const TooltipBox tb = computeTooltip(area.x + key.x, area.y + key.y, key.width, key.height,
+    // Anchor y/h to the whole strip row, not the hovered key: a black key (18px) is shorter
+    // than a white key (30px), and anchoring to the key rect placed the chip 12px higher for
+    // black keys — landing on the keyboard's bottom edge and, near the root, on the badge.
+    const TooltipBox tb = computeTooltip(area.x + key.x, area.y, key.width, area.height,
                                          textW, kTooltipTextH, w, h, TooltipSpec{});
     if (tb.empty()) return;
 
     const Rect box = Rect::ltrb(tb.x, tb.y, tb.x + tb.width, tb.y + tb.height);
     fillSurface(bmp, toKitBox(box), Role::BgCell, InteractionState::Hover);
-    LICE_DrawRect(bmp, box.x, box.y, box.width, box.height,
+    LICE_DrawRect(bmp, box.x, box.y, box.width - 1, box.height - 1,
                   toLice(roleColor(Role::LineHairline)), 1.0f, 0);
     kitTextCentered(bmp, box, label.c_str(), Font::Label, Role::TextPrimary);
 }