Fix #311792, GH#23063: Override alter tag with note tuning value if present

Code revivew issues from musescore#25022, for musescore#6693, that had been ported earlier

Author: Jojo-Schmitz

importexport/musicxml/exportxml.cpp

@@ -3824,27 +3824,22 @@ static void writePitch(XmlWriter& xml, const Note* const note, const bool useDru
       xml.tag(useDrumset  ? "display-step" : "step", step);
       // Check for microtonal accidentals and overwrite "alter" tag
       const Accidental* acc = note->accidental();
-      double alter2 = 0.0;
+      double microtonalAlter  = 0.0;
       if (acc) {
             switch (acc->accidentalType()) {
-                  case AccidentalType::MIRRORED_FLAT:  alter2 = -0.5; break;
-                  case AccidentalType::SHARP_SLASH:    alter2 = 0.5;  break;
-                  case AccidentalType::MIRRORED_FLAT2: alter2 = -1.5; break;
-                  case AccidentalType::SHARP_SLASH4:   alter2 = 1.5;  break;
-                  default:                                             break;
+                  case AccidentalType::MIRRORED_FLAT:  microtonalAlter  = -0.5; break;
+                  case AccidentalType::SHARP_SLASH:    microtonalAlter  =  0.5; break;
+                  case AccidentalType::MIRRORED_FLAT2: microtonalAlter  = -1.5; break;
+                  case AccidentalType::SHARP_SLASH4:   microtonalAlter  =  1.5; break;
+                  default:                                                      break;
                   }
             }
       // Override accidental with explicit note tuning
       qreal tuning = note->tuning();
-      if (fabs(tuning) > 0.01)
-            alter2 = tuning / 100.0;
-      // `alter` represents the "regular" (Western) pitch which can be
-      // 0 (natural), 1 (sharp), -1 (flat), etc. or some other integer depending on transposing instruments.
-      // `alter2` represents a microtone or manually-adjusted note tuning.
-      // In MusicXML, These two values are merged in the same "alter" tag.
-      // https://usermanuals.musicxml.com/MusicXML/Content/EL-MusicXML-alter.htm
-      if (alter || alter2)
-            xml.tag("alter", alter + alter2);
+      if (!qFuzzyIsNull(tuning))
+            microtonalAlter  = tuning / 100.0;
+      if (alter || microtonalAlter )
+            xml.tag("alter", alter + microtonalAlter );
       xml.tag(useDrumset ? "display-octave" : "octave", octave);
       xml.etag();
       }