+/* Return true if 'a' and 'b' sound identical, (even if spelled differently)
+ *
+ * This comparison considers octaves as significant. So Bb and A# in
+ * the same octave are considered enharmonic, but Bb and A# in
+ * different octaves are not. */
+static int
+_pitches_are_enharmonic (pitch_t a, pitch_t b)
+{
+ return _pitch_to_midi (a) == _pitch_to_midi (b);
+}
+
+/* Determine a chord name (if any) from the current notes pressed */
+
+typedef struct analyzed_pitch {
+ /* Original note being analzyed. */
+ pitch_t pitch;
+
+ /* Absolute pitch (expressed as midi number). */
+ int midi_pitch;
+
+ /* Pitch relative to bass note. */
+ int relative_pitch;
+} analyzed_pitch_t;
+
+static int
+_compare_analyzed_pitch_by_midi_pitch (const void *va, const void *vb)
+{
+ const analyzed_pitch_t *a = va, *b = vb;
+
+ return a->midi_pitch - b->midi_pitch;
+}
+
+static int
+_compare_analyzed_pitch_by_relative_pitch (const void *va, const void *vb)
+{
+ const analyzed_pitch_t *a = va, *b = vb;
+
+ return a->relative_pitch - b->relative_pitch;
+}
+
+typedef struct modified_degree
+{
+ int degree;
+ int modification;
+} modified_degree_t;
+
+static int
+_modified_degree_to_half_steps (const modified_degree_t *degree)
+{
+ int half_steps;
+ int scale_degree = degree->degree;
+
+ /* Restrict to actual degrees within a scale. */
+ if (scale_degree > 7)
+ scale_degree = (scale_degree % 8) + 1;
+
+ /* Number of half steps from root to specified degree within a
+ * diatonic scale. */
+ switch (scale_degree) {
+ case 1:
+ half_steps = 0;
+ break;
+ case 2:
+ half_steps = 2;
+ break;
+ case 3:
+ half_steps = 4;
+ break;
+ case 4:
+ half_steps = 5;
+ break;
+ case 5:
+ half_steps = 7;
+ break;
+ case 6:
+ half_steps = 9;
+ break;
+ case 7:
+ half_steps = 11;
+ break;
+ default:
+ fprintf (stderr, "Internal: Invalid degree %d\n", degree->degree);
+ exit (1);
+ break;
+ }
+
+ return half_steps + degree->modification;
+}
+
+/* Number of half steps from 'root' up to 'pitch' (that is, counting
+ * the steps up a chromatic scale), within the same octave. */
+static int
+_pitch_from_root_in_half_steps (pitch_t pitch, pitch_t root)
+{
+ int root_midi = _pitch_to_midi (root);
+ int pitch_midi = _pitch_to_midi (pitch);
+
+ while (pitch_midi < root_midi)
+ pitch_midi += 12;
+
+ return (pitch_midi - root_midi) % 12;
+}
+
+static int
+_chord_signature_matches (analyzed_pitch_t *pitches,
+ int num_pitches,
+ modified_degree_t *degrees,
+ int num_degrees,
+ int inversion,
+ pitch_t *root)
+{
+#define MAX_DEGREES 6
+ int relative_pitches[MAX_DEGREES];
+ int i, root_index;
+
+ assert (num_degrees <= MAX_DEGREES);
+
+ if (num_pitches != num_degrees)
+ return 0;
+
+ if (inversion >= num_degrees)
+ return 0;
+
+ /* We never spell simple intervals as inversions. */
+ if (num_degrees == 2 && inversion > 0)
+ return 0;
+
+ for (i = 0; i < num_degrees; i++) {
+ /* The num_degrees is in the addition just to ensure all
+ * inputs to the modulus operator remain positive. */
+ int index = (i + num_degrees - inversion) % num_degrees;
+
+ /* Again, adding a 12 to keep things positive. */
+ relative_pitches[index] =
+ (12 +
+ _modified_degree_to_half_steps (°rees[i]) -
+ _modified_degree_to_half_steps (°rees[inversion])) % 12;
+
+ }
+
+ for (i = 0; i < num_pitches; i++)
+ if (pitches[i].relative_pitch != relative_pitches[i])
+ return 0;
+
+ root_index = (num_pitches - inversion) % num_pitches;
+ *root = pitches[root_index].pitch;
+
+ return 1;
+}
+
+typedef struct chord_signature
+{
+ int num_degrees;
+ modified_degree_t degrees[MAX_DEGREES];
+ const char *name;
+} chord_signature_t;
+
+/* XXX: The superscript rise value should be relative to the current
+ * font size. Best would be for pango to support this. See:
+ *
+ * https://bugzilla.gnome.org/show_bug.cgi?id=708780
+ *
+ * For now, these are emipirically-derived values that look reasonable
+ * at the default size that score.c is using to draw the staff. If the
+ * user scales the staff up or down then these will look wrong.
+ */
+
+#define SUP "<span font='33' rise='30000'>"
+#define PUS "</span>"
+
+chord_signature_t signatures[] = {
+ /* Octave */
+ { 1, {{1, 0}}, "P8" },
+
+ /* Intervals */
+ { 2, {{1, 0}, {2, -1}}, "m2" },
+ { 2, {{1, 0}, {2, 0}}, "M2" },
+ { 2, {{1, 0}, {3, -1}}, "m3" },
+ { 2, {{1, 0}, {3, 0}}, "M3" },
+ { 2, {{1, 0}, {4, 0}}, "P4" },
+ { 2, {{1, 0}, {5, -1}}, "Tri-tone" },
+ { 2, {{1, 0}, {5, 0}}, "P5" },
+ { 2, {{1, 0}, {6, -1}}, "m6" },
+ { 2, {{1, 0}, {6, 0}}, "M6" },
+ { 2, {{1, 0}, {7, -1}}, "m7" },
+ { 2, {{1, 0}, {7, 0}}, "M7" },
+
+ /* Triads */
+ { 3, {{1, 0}, {4, 0}, {5, 0}}, "sus" },
+ { 3, {{1, 0}, {3, 0}, {5, +1}}, SUP "+" PUS },
+ { 3, {{1, 0}, {3, 0}, {5, 0}}, "" },
+ { 3, {{1, 0}, {3, -1}, {5, 0}}, "m" },
+ { 3, {{1, 0}, {3, -1}, {5, -1}}, "°" },
+ { 3, {{1, 0}, {2, 0}, {5, 0}}, "msus2" },
+
+ /* Seventh chords with no 3rd */
+ { 3, {{1, 0}, {5, +1}, {7, 0}}, SUP "+M7" PUS },
+ { 3, {{1, 0}, {5, +1}, {7, -1}}, SUP "+7" PUS },
+ { 3, {{1, 0}, {5, 0}, {7, 0}}, "M7" },
+ { 3, {{1, 0}, {5, 0}, {7, -1}}, "7" },
+ { 3, {{1, 0}, {5, -1}, {7, -1}}, "7♭5" },
+
+ /* Seventh chords with no 5th */
+ { 3, {{1, 0}, {4, 0}, {7, 0}}, "M7sus" },
+ { 3, {{1, 0}, {4, 0}, {7, -1}}, "7sus" },
+ { 3, {{1, 0}, {3, 0}, {7, 0}}, "M7" },
+ { 3, {{1, 0}, {3, 0}, {7, -1}}, "7" },
+ { 3, {{1, 0}, {3, -1}, {7, 0}}, "m" SUP "M7" PUS },
+ { 3, {{1, 0}, {3, -1}, {7, -1}}, "m7" },
+ { 3, {{1, 0}, {2, 0}, {7, 0}}, "m" SUP "M7" PUS "sus2" },
+ { 3, {{1, 0}, {2, 0}, {7, -1}}, "m7sus2" },
+
+ /* Sixth chords */
+ { 4, {{1, 0}, {4, 0}, {5, 0}, {6, 0}}, "6sus" },
+ { 4, {{1, 0}, {3, 0}, {5, 0}, {6, 0}}, "6" }, /* Ambiguous with m7 */
+ { 4, {{1, 0}, {3, -1}, {5, 0}, {6, 0}}, "m6" },
+ { 4, {{1, 0}, {2, 0}, {5, 0}, {6, 0}}, "m6sus2" },
+
+ /* Seventh chords */
+ { 4, {{1, 0}, {4, 0}, {5, +1}, {7, 0}}, SUP "+M7" PUS "sus" },
+ { 4, {{1, 0}, {4, 0}, {5, +1}, {7, -1}}, SUP "+7" PUS "sus" },
+ { 4, {{1, 0}, {4, 0}, {5, 0}, {7, 0}}, "M7sus" },
+ { 4, {{1, 0}, {4, 0}, {5, 0}, {7, -1}}, "7sus" },
+ { 4, {{1, 0}, {4, 0}, {5, -1}, {7, -1}}, "7♭5sus" },
+ { 4, {{1, 0}, {3, 0}, {5, +1}, {7, 0}}, SUP "+M7" PUS },
+ { 4, {{1, 0}, {3, 0}, {5, +1}, {7, -1}}, SUP "+7" PUS },
+ { 4, {{1, 0}, {3, 0}, {5, 0}, {7, 0}}, "M7" },
+ { 4, {{1, 0}, {3, 0}, {5, 0}, {7, -1}}, "7" },
+ { 4, {{1, 0}, {3, 0}, {5, -1}, {7, -1}}, "7♭5" },
+ { 4, {{1, 0}, {3, -1}, {5, 0}, {7, 0}}, "m" SUP "M7" PUS },
+ { 4, {{1, 0}, {3, -1}, {5, 0}, {7, -1}}, "m7" },
+ { 4, {{1, 0}, {3, -1}, {5, -1}, {7, 0}}, "°" SUP "M7" PUS },
+ { 4, {{1, 0}, {3, -1}, {5, -1}, {7, -1}}, "𝆩" SUP "7" PUS },
+ { 4, {{1, 0}, {3, -1}, {5, -1}, {7, -2}}, "°" SUP "7" PUS },
+ { 4, {{1, 0}, {2, 0}, {5, 0}, {7, 0}}, "m" SUP "M7" PUS "sus2" },
+ { 4, {{1, 0}, {2, 0}, {5, 0}, {7, -1}}, "m7sus2" },
+ { 4, {{1, 0}, {2, 0}, {5, -1}, {7, 0}}, "°" SUP "M7" PUS "sus2" },
+ { 4, {{1, 0}, {2, 0}, {5, -1}, {7, -1}}, "𝆩" SUP "7" PUS "sus2" },
+ { 4, {{1, 0}, {2, 0}, {5, -1}, {7, -2}}, "°" SUP "7" PUS "sus2" }, /* Ambiguous with 7 */
+
+ /* The sorting for chords with degree higher than 9 is funny
+ * to keep the array in degree order after reducing each
+ * degree to an actual scale degree, (9 -> 2, 11 -> 4, 13 ->
+ * 6) */
+
+ /* Ninth chords voiced with no 5th */
+ { 4, {{1, 0}, {9, 0}, {4, 0}, {7, 0}}, "M9sus" },
+ { 4, {{1, 0}, {9, 0}, {4, 0}, {7, -1}}, "9sus" },
+ { 4, {{1, 0}, {9, 0}, {3, 0}, {7, 0}}, "M9" },
+ { 4, {{1, 0}, {9, 0}, {3, 0}, {7, -1}}, "9" },
+ { 4, {{1, 0}, {9, 0}, {3, -1}, {7, 0}}, "m" SUP "M9" PUS },
+ { 4, {{1, 0}, {9, 0}, {3, -1}, {7, -1}}, "m9" },
+ { 4, {{1, 0}, {9, -1}, {3, -1}, {7, -1}}, "m♭9" },
+ { 4, {{1, 0}, {9, 0}, {3, -1}, {6, 0}}, "m6/9" },
+ { 4, {{1, 0}, {9, -1}, {3, -1}, {6, 0}}, "m6/♭9" },
+
+ /* Sixth plus 9 */
+ { 5, {{1, 0}, {9, 0}, {3, 0}, {5, 0}, {6, 0}}, "6/9" },
+ { 5, {{1, 0}, {9, 0}, {3, -1}, {5, 0}, {6, 0}}, "m6/9" },
+ { 5, {{1, 0}, {9, -1}, {3, -1}, {5, 0}, {6, 0}}, "m6/♭9" },
+
+ /* Seventh plus altered 9 */
+ { 5, {{1, 0}, {9, +1}, {3, 0}, {5, 0}, {7, -1}}, "7♯9" },
+ { 5, {{1, 0}, {9, -1}, {3, 0}, {5, 0}, {7, -1}}, "7♭9" },
+ { 5, {{1, 0}, {9, +1}, {3, 0}, {5, -1}, {7, -1}}, "7♭5♯9" },
+ { 5, {{1, 0}, {9, -1}, {3, 0}, {5, -1}, {7, -1}}, "7♭5♭9" },
+
+ /* Ninth chords */
+ { 5, {{1, 0}, {9, 0}, {4, 0}, {5, +1}, {7, 0}}, SUP "+M9" PUS "sus" },
+ { 5, {{1, 0}, {9, 0}, {4, 0}, {5, +1}, {7, -1}}, SUP "+9" PUS "sus" },
+ { 5, {{1, 0}, {9, 0}, {4, 0}, {5, 0}, {7, 0}}, "M9sus" },
+ { 5, {{1, 0}, {9, 0}, {4, 0}, {5, 0}, {7, -1}}, "9sus" },
+ { 5, {{1, 0}, {9, 0}, {3, 0}, {5, +1}, {7, 0}}, SUP "+M9" PUS },
+ { 5, {{1, 0}, {9, 0}, {3, 0}, {5, +1}, {7, -1}}, SUP "+9" PUS },
+ { 5, {{1, 0}, {9, 0}, {3, 0}, {5, 0}, {7, 0}}, "M9" },
+ { 5, {{1, 0}, {9, 0}, {3, 0}, {5, 0}, {7, -1}}, "9" },
+ { 5, {{1, 0}, {9, 0}, {3, -1}, {5, 0}, {7, 0}}, "m" SUP "M9" PUS },
+ { 5, {{1, 0}, {9, 0}, {3, -1}, {5, 0}, {7, -1}}, "m9" },
+ { 5, {{1, 0}, {9, -1}, {3, -1}, {5, 0}, {7, -1}}, "m♭9" },
+ { 5, {{1, 0}, {9, 0}, {3, 0}, {5, -1}, {7, 0}}, "M9" SUP "♭5" PUS },
+ { 5, {{1, 0}, {9, 0}, {3, 0}, {5, -1}, {7, -1}}, "9" SUP "♭5" PUS },
+ { 5, {{1, 0}, {9, 0}, {3, -1}, {5, -1}, {7, 0}}, "m" SUP "M9♭5" PUS },
+ { 5, {{1, 0}, {9, 0}, {3, -1}, {5, -1}, {7, -1}}, "𝆩" SUP "9" PUS },
+ { 5, {{1, 0}, {9, -1}, {3, -1}, {5, -1}, {7, -1}}, "𝆩" SUP "♭9" PUS },
+ { 5, {{1, 0}, {9, 0}, {3, -1}, {5, -1}, {7, -2}}, "°" SUP "9" PUS },
+ { 5, {{1, 0}, {9, -1}, {3, -1}, {5, -1}, {7, -2}}, "°" SUP "♭9" PUS },
+
+ /* Eleventh chords */
+ { 6, {{1, 0}, {9, 0}, {3, 0}, {11, 0}, {5, +1}, {7, 0}}, SUP "+M11" PUS },
+ { 6, {{1, 0}, {9, 0}, {3, 0}, {11, 0}, {5, +1}, {7, -1}}, SUP "+11" PUS },
+ { 6, {{1, 0}, {9, 0}, {3, 0}, {11, 0}, {5, 0}, {7, 0}}, "M11" },
+ { 6, {{1, 0}, {9, 0}, {3, 0}, {11, 0}, {5, 0}, {7, -1}}, "11" },
+ { 6, {{1, 0}, {9, 0}, {3, -1}, {11, 0}, {5, 0}, {7, 0}}, "m" SUP "M11" PUS },
+ { 6, {{1, 0}, {9, 0}, {3, -1}, {11, 0}, {5, 0}, {7, -1}}, "m11" },
+ { 6, {{1, 0}, {9, -1}, {3, -1}, {11, 0}, {5, -1}, {7, -1}}, "𝆩" SUP "11" PUS },
+ { 6, {{1, 0}, {9, -1}, {3, -1}, {11, -1}, {5, -1}, {7, -2}}, "°" SUP "11" PUS }
+};
+