Rebuild the chrome band: full-width piano strip with uniform key widths, note tooltips, one toolbar font

src/core/instrument/ui/keyboard_strip.h

@@ -1,13 +1,14 @@
-// keyboard_strip.h — layout + hit-test + drag math for the editor's keyboard strip.
-// Mirror of embed_strip/mode_switch; the shell draws and marshals mouse events into these
-// functions.
+// 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.
 //
-// The strip maps the full 128-key MIDI span across a horizontal band (the same idiom
-// embed_strip uses). The loaded capture responds across that whole span, so the strip's
-// job is the root marker: click a key, or drag the marker, to set the root.
+// 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.
 
 #pragma once
 
+#include <string>
+
 #include "core/instrument/ui/editor_geometry.h"  // Rect, contains
 
 namespace reasampler::instrument::ui {
@@ -16,35 +17,47 @@ namespace reasampler::instrument::ui {
 // stay independent.
 inline constexpr int kStripKeyCount = 128;
 
-// The keys band takes the whole strip area today; clamped so a degenerate size never
-// yields an inverted rect.
+// Naturals in MIDI 0..127 (C-1 .. G9): ten full octaves of seven, plus C D E F G.
+inline constexpr int kStripWhiteKeyCount = 75;
+
 struct StripLayout {
-    Rect keys;
+    Rect band;   // the surface handed in, edge to edge
+    Rect keys;   // the tiled key area, kStripWhiteKeyCount * whiteWidth, centred in band
+    int whiteWidth = 0;
+    int blackWidth = 0;
+    int blackHeight = 0;  // black keys are short; below them the white key answers
 };
 
-// Divide a (w x h) strip area into its regions. Pure.
+// Divide a (w x h) strip area into its key geometry. Pure. A band too narrow for one pixel
+// per white key yields empty `keys` — nothing draws and nothing hit-tests.
 StripLayout layoutStrip(int w, int h);
 
-// x pixel of the LEFT edge of key `note` (0..127) under the linear 128-key map; key N
-// occupies [keyLeftX(N), keyLeftX(N+1)). note==128 maps to the band's right edge.
-int keyLeftX(const StripLayout& layout, int note);
+// True when `note` (clamped to [0,127]) is a natural (white) key in 12-tone equal
+// temperament; false for an accidental (black) key.
+bool isNaturalKey(int note);
 
-// Half-open rect of a single key `note`, clamped to [0,127].
+// Naturals strictly below `note`. For a white key that is its own ordinal; for a black key
+// it is the white-key boundary the accidental straddles.
+int whiteIndexOf(int note);
+
+// Rect of a single key, clamped to [0,127]. Whites are full band height and whiteWidth
+// wide; blacks are blackHeight tall and blackWidth wide, centred on their boundary.
 Rect keyRect(const StripLayout& layout, int note);
 
 // Root-marker rect; equivalent to keyRect(layout, rootNote) but named so the intent reads
 // at the call site.
 Rect rootMarkerRect(const StripLayout& layout, int rootNote);
 
-// MIDI note a point (x, y) lands on, or -1 outside the keys band.
+// MIDI note a point (x, y) lands on, or -1 outside the tiled keys. A black key wins inside
+// its own short zone; anywhere else the white key beneath answers.
 int keyAtPoint(const StripLayout& layout, int x, int y);
 
-// Resolves a drag to a new MIDI note: `startNote` shifted by round(dxPixels / keyWidth),
-// clamped to [0,127]. The one arithmetic behind the root-marker drag.
-int resolveDragNote(const StripLayout& layout, int startNote, int dxPixels);
+// The note a live drag resolves to: keyAtPoint with the point clamped into the key area, so
+// a drag that wanders off the strip keeps tracking rather than dropping the edit. -1 only
+// when there is no key area at all.
+int resolveDragNote(const StripLayout& layout, int x, int y);
 
-// True when `note` (clamped to [0,127]) is a natural (white) key in 12-tone equal
-// temperament; false for an accidental (black) key.
-bool isNaturalKey(int note);
+// DAW convention (the one REAPER uses): MIDI 60 is C4, so MIDI 0 is C-1.
+std::string noteName(int note);
 
 }  // namespace reasampler::instrument::ui