Add enums and API for modulator transform type

include/fluidsynth/mod.h

@@ -57,6 +57,15 @@ enum fluid_mod_flags
     FLUID_MOD_SIN = 0x80,            /**< Custom non-standard sinus mapping function */
 };
 
+/**
+ * Transform types for the SoundFont2 modulators.
+ */
+enum fluid_mod_transforms
+{
+    FLUID_MOD_LINEAR_TRANSFORM = 0, /* **< Linear: directly add the computed value to summing node */
+    FLUID_MOD_ABS_VALUE = 2     /* **< Absolute value: add abs of the computed value */
+};
+
 /**
  * General controller (if #FLUID_MOD_GC in flags).  This
  * corresponds to SoundFont 2.04 PDF section 8.2.1
@@ -83,13 +92,15 @@ FLUIDSYNTH_API void fluid_mod_set_source1(fluid_mod_t *mod, int src, int flags);
 FLUIDSYNTH_API void fluid_mod_set_source2(fluid_mod_t *mod, int src, int flags);
 FLUIDSYNTH_API void fluid_mod_set_dest(fluid_mod_t *mod, int dst);
 FLUIDSYNTH_API void fluid_mod_set_amount(fluid_mod_t *mod, double amount);
+FLUIDSYNTH_API void fluid_mod_set_transform(fluid_mod_t *mod, int type);
 
 FLUIDSYNTH_API int fluid_mod_get_source1(const fluid_mod_t *mod);
 FLUIDSYNTH_API int fluid_mod_get_flags1(const fluid_mod_t *mod);
 FLUIDSYNTH_API int fluid_mod_get_source2(const fluid_mod_t *mod);
 FLUIDSYNTH_API int fluid_mod_get_flags2(const fluid_mod_t *mod);
 FLUIDSYNTH_API int fluid_mod_get_dest(const fluid_mod_t *mod);
 FLUIDSYNTH_API double fluid_mod_get_amount(const fluid_mod_t *mod);
+FLUIDSYNTH_API int fluid_mod_get_transform(fluid_mod_t *mod);
 
 FLUIDSYNTH_API int fluid_mod_test_identity(const fluid_mod_t *mod1, const fluid_mod_t *mod2);
 FLUIDSYNTH_API int fluid_mod_has_source(const fluid_mod_t *mod, int cc, int ctrl);

src/sfloader/fluid_defsfont.c

@@ -1648,8 +1648,20 @@ fluid_zone_mod_import_sfont(char *zone_name, fluid_mod_t **mod, SFZone *sfzone)
             mod_dest->flags2 &= ~FLUID_MOD_BIPOLAR;
         }
 
-        /* *** Transform Type *** */
-        mod_dest->trans = mod_src->trans;
+        /**
+         * *** Transform Type ***
+         * Only 2 types of transform are defined in the sf2 specification.
+         */
+        if(mod_src->trans != FLUID_MOD_LINEAR_TRANSFORM && mod_src->trans != FLUID_MOD_ABS_VALUE)
+        {
+            /* disable the modulator as the transform is invalid */
+            mod_dest->amount = 0;
+            mod_dest->trans = FLUID_MOD_LINEAR_TRANSFORM;
+        }
+        else
+        {
+            mod_dest->trans = mod_src->trans;
+        }
 
         /* Store the new modulator in the zone The order of modulators
          * will make a difference, at least in an instrument context: The

src/synth/fluid_mod.c

@@ -98,6 +98,24 @@ fluid_mod_set_amount(fluid_mod_t *mod, double amount)
     mod->amount = (double) amount;
 }
 
+/**
+ * Set the transform type of a modulator.
+ *
+ * @param mod The modulator instance
+ * @param type Transform type
+ */
+void
+fluid_mod_set_transform(fluid_mod_t *mod, int type)
+{
+    unsigned char flag = (unsigned char) type;
+    if(flag != FLUID_MOD_LINEAR_TRANSFORM && flag != FLUID_MOD_ABS_VALUE)
+    {
+        /* invalid transform */
+        return;
+    }
+    mod->trans = flag;
+}
+
 /**
  * Get the primary source value from a modulator.
  *
@@ -170,6 +188,18 @@ fluid_mod_get_amount(const fluid_mod_t *mod)
     return (double) mod->amount;
 }
 
+/**
+ * Get the transform type of a modulator.
+ *
+ * @param mod The modulator instance
+ * @return Transform type
+ */
+int
+fluid_mod_get_transform(fluid_mod_t *mod)
+{
+    return (int) mod->trans;
+}
+
 /*
  * retrieves the initial value from the given source of the modulator
  */
@@ -474,10 +504,11 @@ fluid_mod_get_value(fluid_mod_t *mod, fluid_voice_t *voice)
 
     /* it indeed is as simple as that: */
     final_value = (fluid_real_t) mod->amount * v1 * v2;
-    /* check for absolute value transform*/
-    if(mod->trans == 2)
+
+    /* check for absolute value transform */
+    if(mod->trans == FLUID_MOD_ABS_VALUE)
     {
-        final_value = fabs(final_value);
+        final_value = FLUID_FABS(final_value);
     }
     return final_value;
 }
@@ -497,7 +528,8 @@ new_fluid_mod(void)
         FLUID_LOG(FLUID_ERR, "Out of memory");
         return NULL;
     }
-
+    // for the sake of backward compatibility
+    mod->trans = FLUID_MOD_LINEAR_TRANSFORM;
     return mod;
 }