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

CMakeLists.txt

@@ -1034,7 +1034,7 @@ target_link_libraries(capture_browser_tests PRIVATE capture_browser)
 add_test(NAME capture_browser_tests COMMAND capture_browser_tests)
 
 add_executable(keyboard_strip_tests tests/test_keyboard_strip.cpp)
-target_link_libraries(keyboard_strip_tests PRIVATE keyboard_strip)
+target_link_libraries(keyboard_strip_tests PRIVATE keyboard_strip sample_bands)
 add_test(NAME keyboard_strip_tests COMMAND keyboard_strip_tests)
 
 # waveform_view (S11): the pure marker geometry + zero-crossing snap. Links waveform_view (+

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   for both — do not reintroduce either superseded design.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);
 }

tests/test_keyboard_strip.cpp

@@ -2,14 +2,23 @@
 // framework. Same fast assert loop as the sibling pure tests.
 //
 // Covers: layoutStrip (normal, degenerate, sub-key-width); same-class key-width uniformity
-// swept across editor widths AND DPI scale factors; the tiled key area staying centred
+// swept across editor client widths (including multiples of them, standing in for larger
+// client sizes — see the client-pixel-only note below); the tiled key area staying centred
 // inside a band that spans the full width it was handed; whiteIndexOf / isNaturalKey across
 // octave boundaries and the 0..127 extremes; keyRect tiling and black-over-white overlap;
 // keyAtPoint resolving black-over-white by zone and missing off-band; the root affordance's
-// hit-to-marker round trip; resolveDragNote clamping a wandering pointer; and noteName under
-// the C4 (MIDI 60) DAW convention.
+// hit-to-marker round trip; resolveDragNote clamping a wandering pointer; noteName under the
+// C4 (MIDI 60) DAW convention; and the gutter pinned at the shipped default window size.
+//
+// Client-pixel-only guarantee: every width swept below is a CLIENT-pixel width. Nothing in
+// the instrument implements IPlugViewContentScaleSupport, so if a host scales the plugin
+// window itself, uniform integer key widths get resampled at the physical-pixel level —
+// unverified by this suite (see src/core/instrument/CLAUDE.md).
 
 #include "../src/core/instrument/ui/keyboard_strip.h"
+#include "../src/core/instrument/ui/sample_bands.h"  // kPad, to derive the strip width the
+                                                       // shipped default window (840x620,
+                                                       // editor_session.cpp) hands the strip
 
 #include <cstdio>
 #include <string>
@@ -24,11 +33,12 @@ static int g_fail = 0;
 // A comfortable strip: wide enough that every class is several pixels across.
 static StripLayout wideStrip() { return layoutStrip(1280, 30); }
 
-// The widths a real editor hands the strip — the 560px minimum client up to a wide
-// window — crossed with the DPI scale factors Windows actually reports.
+// The widths a real editor hands the strip — the 560px minimum client up to a wide window.
 static const int kBaseWidths[] = {544, 600, 640, 700, 749, 750, 751, 824, 900, 1000,
                                   1024, 1103, 1264, 1600, 1920, 2400};
-static const double kDpiScales[] = {1.0, 1.25, 1.5, 1.75, 2.0};
+// Multiplies each base width to widen client-pixel coverage (e.g. a maximized/larger client
+// area) — NOT a host DPI/content-scale factor; see the client-pixel-only note above.
+static const double kWidthMultipliers[] = {1.0, 1.25, 1.5, 1.75, 2.0};
 
 // --- layoutStrip --------------------------------------------------------------
 
@@ -61,11 +71,11 @@ static void testDegenerateSizesYieldNoKeys() {
     CHECK(keyAtPoint(narrow, 10, 10) == -1);
 }
 
-// --- the sharp one: same-class widths are uniform at every width and DPI scale ---
+// --- the sharp one: same-class widths are uniform at every client width tested ---
 
-static void testSameClassKeysAreEqualWidthAcrossWidthsAndDpiScales() {
+static void testSameClassKeysAreEqualWidthAcrossClientWidths() {
     for (const int base : kBaseWidths) {
-        for (const double scale : kDpiScales) {
+        for (const double scale : kWidthMultipliers) {
             const int w = static_cast<int>(base * scale);
             const int h = static_cast<int>(30 * scale);
             const StripLayout L = layoutStrip(w, h);
@@ -98,7 +108,7 @@ static void testSameClassKeysAreEqualWidthAcrossWidthsAndDpiScales() {
 
 static void testKeyAreaSpansTheBandWithinOneKeyAtEveryTestedWidth() {
     for (const int base : kBaseWidths) {
-        for (const double scale : kDpiScales) {
+        for (const double scale : kWidthMultipliers) {
             const int w = static_cast<int>(base * scale);
             const StripLayout L = layoutStrip(w, 30);
             CHECK(L.band.width == w);  // the strip always spans the width it was handed
@@ -268,10 +278,32 @@ static void testNoteNamesFollowTheC4Convention() {
     CHECK(noteName(500) == "G9");
 }
 
+// --- the gutter at the shipped default window size -----------------------------
+
+// The rule-based sweep above pins `margins == w % 75` and `leftMargin == margins/2` at every
+// width, but pins no concrete number — Daniel is making a visual call on the specific gutter
+// at the shipped default, and neither kPad nor the 840 default is covered by another test
+// firing if either ever changes. The strip is a sawtooth with period kStripWhiteKeyCount (75)
+// px of window width, and the shipped 840 default lands on residue 74 — the cycle's maximum:
+// one pixel of resize (840->841) collapses both gutters to zero and grows every white key
+// from 10px to 11px.
+static void testGutterAtTheShippedDefaultWindowSize() {
+    constexpr int kShippedDefaultWindowW = 840;  // editor_session.cpp's ViewRect default
+    const int stripW = kShippedDefaultWindowW - 2 * kPad;  // chromeRects insets rootStrip by kPad
+    CHECK(stripW == 824);
+
+    const StripLayout L = layoutStrip(stripW, 30);
+    CHECK(L.whiteWidth == 10);
+    const int margins = L.band.width - L.keys.width;
+    CHECK(margins == 74);
+    const int leftMargin = L.keys.x - L.band.x;
+    CHECK(leftMargin == 37);
+}
+
 int main() {
     testLayoutFillsTheBandAndCentresTheKeys();
     testDegenerateSizesYieldNoKeys();
-    testSameClassKeysAreEqualWidthAcrossWidthsAndDpiScales();
+    testSameClassKeysAreEqualWidthAcrossClientWidths();
     testKeyAreaSpansTheBandWithinOneKeyAtEveryTestedWidth();
     testIsNaturalKeyAcrossAnOctaveAndTheExtremes();
     testWhiteIndexCountsNaturalsBelowTheNote();
@@ -284,6 +316,7 @@ int main() {
     testHitTestingAKeyMarksThatSameKey();
     testDragTracksThePointerAndClampsWhenItWanders();
     testNoteNamesFollowTheC4Convention();
+    testGutterAtTheShippedDefaultWindowSize();
 
     if (g_fail == 0) {
         std::printf("keyboard_strip: all tests passed\n");