+ /* We express Controllable values in one of three ways:
+ * 1. `user' --- as presented to the user (e.g. dB, Hz, etc.)
+ * 2. `interface' --- as used in some cases for the UI representation
+ * (in order to make controls behave logarithmically).
+ * 3. `internal' --- as passed to a processor, track, plugin, or whatever.
+ *
+ * Note that in some cases user and processor may be the same
+ * (and interface different) e.g. frequency, which is presented
+ * to the user and passed to the processor in linear terms, but
+ * which needs log scaling in the interface.
+ *
+ * In other cases, user and interface may be the same (and processor different)
+ * e.g. gain, which is presented to the user in log terms (dB)
+ * but passed to the processor as a linear quantity.
+ */
+
+ /** Set `internal' value */
+ virtual void set_value (double) = 0;
+ /** @return `internal' value */
+ virtual double get_value (void) const = 0;
+
+ PBD::Signal0<void> LearningFinished;
+ static PBD::Signal3<void,PBD::Controllable*,int,int> CreateBinding;
+ static PBD::Signal1<void,PBD::Controllable*> DeleteBinding;
+
+ static PBD::Signal1<bool,PBD::Controllable*> StartLearning;
+ static PBD::Signal1<void,PBD::Controllable*> StopLearning;
+
+ static PBD::Signal1<void,Controllable*> Destroyed;
+
+ PBD::Signal0<void> Changed;
+
+ int set_state (const XMLNode&, int version);
+ XMLNode& get_state ();