From: Carl Worth <cworth@cworth.org>
Date: Tue, 1 Oct 2013 18:14:41 +0000 (-0700)
Subject: Automatically change key whenever user plays a major scale.
X-Git-Url: https://git.cworth.org/git?p=scherzo;a=commitdiff_plain;h=e61e2b33d79fd2c55521ef46432ef3c40f3efc5b

Automatically change key whenever user plays a major scale.

This is a very convenient way to access this functionality directly
from the piano keyboard, without having to use the computer keyboard
at all.
---

diff --git a/scherzo.c b/scherzo.c
index 95bab27..6657959 100644
--- a/scherzo.c
+++ b/scherzo.c
@@ -971,11 +971,52 @@ scherzo_update_notes_and_chord (scherzo_t *scherzo)
     talloc_free (local);
 }
 
+static void
+scherzo_set_key (scherzo_t *scherzo, pitch_t pitch)
+{
+    scherzo_key_init (&scherzo->key, pitch);
+    score_set_key (scherzo->score, pitch);
+}
+
+static bool
+pitches_are_diatonic_scale (pitch_t *pitches, int num_pitches)
+{
+    int diatonic_half_steps[7] = {
+	0, 2, 4, 5, 7, 9, 11
+    };
+    int half_steps;
+    pitch_t root;
+    int i;
+
+    if (num_pitches < 7)
+	return 0;
+
+    root = pitches[0];
+
+    for (i = 0; i < 7; i++) {
+	half_steps = pitch_from_root_in_half_steps (pitches[i], root);
+	if (half_steps != diatonic_half_steps[i])
+	    return false;
+    }
+
+    return true;
+}
+
 static void
 scherzo_press_note (scherzo_t *scherzo, pitch_t pitch)
 {
     int i;
 
+#define NUM_RECENT_PITCHES 7
+    static pitch_t recent_pitches[NUM_RECENT_PITCHES];
+
+    memmove (recent_pitches, recent_pitches + 1,
+	     (NUM_RECENT_PITCHES - 1) * sizeof (pitch_t));
+    recent_pitches[NUM_RECENT_PITCHES - 1] = pitch;
+
+    if (pitches_are_diatonic_scale (recent_pitches, NUM_RECENT_PITCHES))
+	scherzo_set_key (scherzo, recent_pitches[0]);
+
     /* Do nothing if this note is already pressed. */
     for (i = 0; i < scherzo->notes_pressed.num_pitches; i++)
 	if (scherzo->notes_pressed.pitches[i] == pitch)
@@ -1246,8 +1287,7 @@ main (int argc, char *argv[])
     scherzo.pedal_pressed = 0;
 
     /* Default to key of C Major, naturally. */
-    scherzo_key_init (&scherzo.key, PITCH_CLASS_LITERAL (C, NATURAL));
-    score_set_key (scherzo.score, scherzo.key.pitch);
+    scherzo_set_key (&scherzo, PITCH_CLASS_LITERAL (C, NATURAL));
 
     mnemon_init (&scherzo.mnemon);
     /* XXX: Should create a default file if one cannot be loaded. */