Extract pitchDifftoKeyWheelSteps as a function

src/track/keyutils.cpp

@@ -737,23 +737,19 @@ double KeyUtils::trackSimilarity(mixxx::track::io::key::ChromaticKey key1,
 
     const int roundedPitchDiff = normalizePitch(round(pitchDiff));
     double cents = abs(roundedPitchDiff - pitchDiff);
+    // bring cents value back to [0-0.5] for pitchDiff values > 11.50
     if (cents > 11) {
         cents = 12 - cents;
     }
 
-    // Open Key number also conveniently gives us the index in the Keywheel
-    // Keys use 1-based indexing (0 is INVALID)
-    const int okNum = keyToOpenKeyNumber(keyFromNumericValue(roundedPitchDiff + 1));
-    // rank: distance between tracks on the Circle of Fifths,
-    // when played at the same tempo.
-    const int rank = std::min(okNum, 12 - okNum);
+    const int keyWheelSteps = pitchDiffToKeywheelSteps(roundedPitchDiff);
 
-    // normalize rank between 0-1 by dividing by 7 (no. of rank values, including 0)
+    // normalize between 0-1 by dividing by 7 (no. of steps values, including 0)
     // invert so 1.0 means most compatible
-    const double normRank = (1 - rank / 7);
+    const double normKWSteps = (1 - keyWheelSteps / 7);
     // this 1-16x^4 curve forgives the effect of lower detune values on the similarity
     const double normCents = (1 - 16 * pow(cents, 4)); // 0-1
 
     // calculate final similarity and return it
-    return normRank * normCents;
+    return normKWSteps * normCents;
 }

src/track/keyutils.h

@@ -62,6 +62,15 @@ class KeyUtils {
         return openKeyNumberToKey(keyToOpenKeyNumber(key), true);
     }
 
+    // Given pitch difference of 2 keys, returns their distance on the keywheel
+    static inline int pitchDiffToKeywheelSteps(int pitchDiff) {
+        // Open Key number also conveniently gives us the clockwise index in the Keywheel
+        // Keys use 1-based indexing (0 is INVALID)
+        const int CWSteps = keyToOpenKeyNumber(keyFromNumericValue(pitchDiff + 1));
+        // it's a wheel, so check if counter-clockwise direction has fewer steps
+        return std::min(CWSteps, 12 - CWSteps);
+    }
+
     static QString keyToString(mixxx::track::io::key::ChromaticKey key,
                                KeyNotation notation = KeyNotation::Custom);