1 files changed, 38 insertions, 2 deletions
diff --git a/libs/ardour/ardour/audio_backend.h b/libs/ardour/ardour/audio_backend.h
index 0e39625e8c..cbe0bfce50 100644
--- a/libs/ardour/ardour/audio_backend.h
+++ b/libs/ardour/ardour/audio_backend.h
@@ -239,7 +239,38 @@ class AudioBackend : public PortEngine {
      * app is undefined or cannot be launched.
      */
     virtual void launch_control_app () = 0;
-    /* Basic state control */
+
+    /* @return a vector of strings that describe the available
+     * MIDI options. 
+     *
+     * These can be presented to the user to decide which
+     * MIDI drivers, options etc. can be used. The returned strings
+     * should be thought of as the key to a map of possible
+     * approaches to handling MIDI within the backend. Ensure that
+     * the strings will make sense to the user.
+     */
+    virtual std::vector<std::string> enumerate_midi_options () const = 0;
+
+    /* Request the use of the MIDI option named @param option, which
+     * should be one of the strings returned by enumerate_midi_options()
+     *
+     * @return zero if successful, non-zero otherwise
+     */
+    virtual int set_midi_option (const std::string& option) = 0;
+
+    virtual std::string midi_option () const = 0;
+    
+    /* State Control */
+
+    /* non-virtual method to avoid possible overrides of default
+     * parameters. See Scott Meyers or other books on C++ to
+     * understand this pattern, or possibly just this:
+     *
+     * http://stackoverflow.com/questions/12139786/good-pratice-default-arguments-for-pure-virtual-method
+     */ 
+    int start (bool for_latency_measurement=false) {
+	    return _start (for_latency_measurement);
+    }
 
     /** Start using the device named in the most recent call
      * to set_device(), with the parameters set by various
@@ -250,9 +281,14 @@ class AudioBackend : public PortEngine {
      * the AudioEngine referenced by @param engine. These calls will
      * occur in a thread created by and/or under the control of the backend.
      *
+     * @param for_latency_measurement if true, the device is being started
+     *        to carry out latency measurements and the backend should this
+     *        take care to return latency numbers that do not reflect
+     *        any existing systemic latency settings.
+     *
      * Return zero if successful, negative values otherwise.
      */
-    virtual int start () = 0;
+    virtual int _start (bool for_latency_measurement) = 0;
 
     /** Stop using the device currently in use. 
      *