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

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");