Fix a problem where mappings didn't span tuning center

If a partial mapping existed and the mapping didnt span
the tuning center (so like you mapped 69-81 with a tuning
center of 60) we were off by an octave. This fix pushes
the mapping to span the tuning center.

Closes #72
Addresses surge-synthesizer/surge#7822

include/TuningsImpl.h

@@ -466,6 +466,28 @@ inline Tuning::Tuning(const Scale &s_, const KeyboardMapping &k_, bool allowTuni
         throw TuningError("Unable to tune to a scale with no notes. Your scale provided " +
                           std::to_string(s.count) + " notes.");
 
+    int useMiddleNote{k.middleNote};
+    if (k.count > 0)
+    {
+        // Is the KBM not spanning the tuning note
+        auto mapStart = useMiddleNote;
+        auto mapEnd = useMiddleNote + k.count;
+        while (mapStart > k.tuningConstantNote)
+        {
+            useMiddleNote -= k.count;
+            mapStart = useMiddleNote;
+            mapEnd = useMiddleNote + k.count;
+            // throw std::logic_error("Blah");
+        }
+        while (mapEnd < k.tuningConstantNote)
+        {
+            useMiddleNote += k.count;
+            mapStart = useMiddleNote;
+            mapEnd = useMiddleNote + k.count;
+            // throw std::logic_error("Blah");
+        }
+    }
+
     int kbmRotations{1};
     for (const auto &kv : k.keys)
     {
@@ -512,11 +534,11 @@ inline Tuning::Tuning(const Scale &s_, const KeyboardMapping &k_, bool allowTuni
     double pitches[N];
 
     int posPitch0 = 256 + k.tuningConstantNote;
-    int posScale0 = 256 + k.middleNote;
+    int posScale0 = 256 + useMiddleNote;
 
     double pitchMod = log(k.tuningPitch) / log(2) - 1;
 
-    int scalePositionOfTuningNote = k.tuningConstantNote - k.middleNote;
+    int scalePositionOfTuningNote = k.tuningConstantNote - useMiddleNote;
     if (k.count > 0)
     {
         while (scalePositionOfTuningNote >= k.count)
@@ -676,10 +698,12 @@ inline Tuning::Tuning(const Scale &s_, const KeyboardMapping &k_, bool allowTuni
                 ** If we mod that by the mapping size we know which note we are on
                 */
                 int mappingKey = distanceFromScale0 % k.count;
+                int rotations = 0;
                 if (mappingKey < 0)
+                {
                     mappingKey += k.count;
+                }
                 // Now have we gone off the end
-                int rotations = 0;
                 int dt = distanceFromScale0;
                 if (dt > 0)
                 {

tests/alltests.cpp

@@ -1150,6 +1150,7 @@ TEST_CASE("Skipped Note and Root")
         REQUIRE(t.isMidiNoteMapped(60));
         REQUIRE(t.isMidiNoteMapped(69));
         REQUIRE(t.frequencyForMidiNote(69) == Approx(440.0).margin(0.01));
+        REQUIRE(t.frequencyForMidiNote(60) == Approx(246.9416506281).margin(0.01));
     }
 
     SECTION("Tuning from 59 throws")
@@ -1185,6 +1186,7 @@ TEST_CASE("Skipped Note and Root")
         auto t = Tunings::Tuning(s, k);
         REQUIRE(t.isMidiNoteMapped(60));
         REQUIRE(t.isMidiNoteMapped(69));
+        REQUIRE(t.frequencyForMidiNote(60) == Approx(246.9416506281).margin(0.01));
         REQUIRE(t.frequencyForMidiNote(69) == Approx(440.0).margin(0.01));
     }
 
@@ -1196,6 +1198,7 @@ TEST_CASE("Skipped Note and Root")
         t = t.withSkippedNotesInterpolated();
         REQUIRE(t.isMidiNoteMapped(60));
         REQUIRE(t.isMidiNoteMapped(69));
+        REQUIRE(t.frequencyForMidiNote(60) == Approx(246.9416506281).margin(0.01));
         REQUIRE(t.frequencyForMidiNote(69) == Approx(440.0).margin(0.01));
     }
 }
@@ -1338,3 +1341,23 @@ TEST_CASE("Retuning API")
         }
     }
 }
+
+TEST_CASE("Surge 7822 non uniform mapping misses scale center")
+{
+    SECTION("At Note 57 - no wrapping")
+    {
+        auto scale = Tunings::readSCLFile(testFile("kbm-wrapping-7822/31edo2.scl"));
+        auto map = Tunings::readKBMFile(testFile("kbm-wrapping-7822/31edo2-subset-57.kbm"));
+        auto t = Tunings::Tuning(scale, map);
+        REQUIRE(t.frequencyForMidiNote(60) == Approx(400.0));
+        REQUIRE(t.frequencyForMidiNote(61) == Approx(418.2936581199));
+    }
+    SECTION("At Note 69 - wrapping")
+    {
+        auto scale = Tunings::readSCLFile(testFile("kbm-wrapping-7822/31edo2.scl"));
+        auto map = Tunings::readKBMFile(testFile("kbm-wrapping-7822/31edo2-subset.kbm"));
+        auto t = Tunings::Tuning(scale, map);
+        REQUIRE(t.frequencyForMidiNote(60) == Approx(400.0));
+        REQUIRE(t.frequencyForMidiNote(61) == Approx(418.2936581199));
+    }
+}

tests/data/kbm-wrapping-7822/31edo2-subset-57.kbm

@@ -0,0 +1,29 @@
+! foo.kbm
+! 
+! Size of map:
+12
+! First MIDI note number to retune:
+0
+! Last MIDI note number to retune:
+127
+! Middle note where the first entry in the mapping is mapped to:
+57
+! Reference note for which frequency is given:
+60
+! Frequency to tune the above note to (floating point e.g. 440.0):
+400
+! Scale degree to consider as formal octave:
+31
+! Mapping.
+0
+3
+5
+8
+10
+13
+16
+18
+21
+23
+26
+28

tests/data/kbm-wrapping-7822/31edo2-subset.kbm

@@ -0,0 +1,29 @@
+! foo.kbm
+! 
+! Size of map:
+12
+! First MIDI note number to retune:
+0
+! Last MIDI note number to retune:
+127
+! Middle note where the first entry in the mapping is mapped to:
+69
+! Reference note for which frequency is given:
+60
+! Frequency to tune the above note to (floating point e.g. 440.0):
+400
+! Scale degree to consider as formal octave:
+31
+! Mapping.
+0
+3
+5
+8
+10
+13
+16
+18
+21
+23
+26
+28

tests/data/kbm-wrapping-7822/31edo2.scl

@@ -0,0 +1,36 @@
+! foo.scl
+!
+
+ 31
+!
+ 38.70968
+ 77.41935
+ 116.12903
+ 154.83871
+ 193.54839
+ 232.25806
+ 270.96774
+ 309.67742
+ 348.38710
+ 387.09677
+ 425.80645
+ 464.51613
+ 503.22581
+ 541.93548
+ 580.64516
+ 619.35484
+ 658.06452
+ 696.77419
+ 735.48387
+ 774.19355
+ 812.90323
+ 851.61290
+ 890.32258
+ 929.03226
+ 967.74194
+ 1006.45161
+ 1045.16129
+ 1083.87097
+ 1122.58065
+ 1161.29032
+ 2/1