start work on the changes to EngineControl (dialog) to integrate with new backend design, and add "requires-driver" concept to AudioBackend to handle JACK specifically

gtk2_ardour/ardev_common.sh.in

@@ -17,6 +17,7 @@ export ARDOUR_DATA_PATH=$TOP:$TOP/build:$TOP/gtk2_ardour:$TOP/build/gtk2_ardour:
 export ARDOUR_MIDIMAPS_PATH=$TOP/midi_maps:.
 export ARDOUR_MCP_PATH=$TOP/mcp:.
 export ARDOUR_EXPORT_FORMATS_PATH=$TOP/export:.
+export ARDOUR_BACKEND_PATH=$TOP/build/libs/ardour
 
 #
 # even though we set the above variables, ardour requires that these 

gtk2_ardour/ardour_ui.cc

@@ -397,7 +397,6 @@ ARDOUR_UI::attach_to_engine ()
 	engine->SampleRateChanged.connect (forever_connections, MISSING_INVALIDATOR, boost::bind (&ARDOUR_UI::update_sample_rate, this, _1), gui_context());
 
 	engine->Halted.connect_same_thread (forever_connections, boost::bind (&ARDOUR_UI::engine_halted, this, _1, false));
-	engine->BackendAvailable.connect_same_thread (forever_connections, boost::bind (&ARDOUR_UI::post_engine, this));
 
 	ARDOUR::Port::set_connecting_blocked (ARDOUR_COMMAND_LINE::no_connect_ports);
 

gtk2_ardour/engine_dialog.h

@@ -47,80 +47,67 @@ class EngineControl : public Gtk::VBox {
 	void set_state (const XMLNode&);
 
   private:
-	Gtk::Adjustment periods_adjustment;
+    /* core fields used by all backends */
-	Gtk::SpinButton periods_spinner;
-	Gtk::Adjustment ports_adjustment;
-	Gtk::SpinButton ports_spinner;
-	Gtk::Adjustment input_latency_adjustment;
-	Gtk::SpinButton input_latency;
-	Gtk::Adjustment output_latency_adjustment;
-	Gtk::SpinButton output_latency;
-	Gtk::Label latency_label;
 
-	Gtk::CheckButton realtime_button;
+    Gtk::ComboBoxText backend_combo;
-	Gtk::CheckButton no_memory_lock_button;
+    Gtk::ComboBoxText input_device_combo;
-	Gtk::CheckButton unlock_memory_button;
+    Gtk::ComboBoxText output_device_combo;
-	Gtk::CheckButton soft_mode_button;
+    Gtk::ComboBoxText sample_rate_combo;
-	Gtk::CheckButton monitor_button;
+    Gtk::ComboBoxText buffer_size_combo;
-	Gtk::CheckButton force16bit_button;
+    Gtk::Adjustment input_latency_adjustment;
-	Gtk::CheckButton hw_monitor_button;
+    Gtk::SpinButton input_latency;
-	Gtk::CheckButton hw_meter_button;
+    Gtk::Adjustment output_latency_adjustment;
-	Gtk::CheckButton verbose_output_button;
+    Gtk::SpinButton output_latency;
+    Gtk::Adjustment input_channels_adjustment;
+    Gtk::SpinButton input_channels;
+    Gtk::Adjustment output_channels_adjustment;
+    Gtk::SpinButton output_channels;
+    Gtk::Adjustment ports_adjustment;
+    Gtk::SpinButton ports_spinner;
+    Gtk::Label latency_label;
 
-	Gtk::Button start_button;
+    /* JACK specific */
-	Gtk::Button stop_button;
+    
-	Gtk::HButtonBox button_box;
+    Gtk::CheckButton realtime_button;
+    Gtk::CheckButton no_memory_lock_button;
+    Gtk::CheckButton unlock_memory_button;
+    Gtk::CheckButton soft_mode_button;
+    Gtk::CheckButton monitor_button;
+    Gtk::CheckButton force16bit_button;
+    Gtk::CheckButton hw_monitor_button;
+    Gtk::CheckButton hw_meter_button;
+    Gtk::CheckButton verbose_output_button;
+    
+    
+    Gtk::ComboBoxText preset_combo;
+    Gtk::ComboBoxText serverpath_combo;
+    Gtk::ComboBoxText driver_combo;
+    Gtk::ComboBoxText interface_combo;
+    Gtk::ComboBoxText timeout_combo;
+    Gtk::ComboBoxText dither_mode_combo;
+    Gtk::ComboBoxText audio_mode_combo;
+    Gtk::ComboBoxText midi_driver_combo;
+    
+    Gtk::Table basic_packer;
+    Gtk::Table options_packer;
+    Gtk::Table device_packer;
+    Gtk::HBox basic_hbox;
+    Gtk::HBox options_hbox;
+    Gtk::HBox device_hbox;
+    Gtk::Notebook notebook;
+    
+    bool _used;
+    
+    static bool engine_running ();
+    
+    void driver_changed ();
+    void backend_changed ();
 
-	Gtk::ComboBoxText sample_rate_combo;
+    void redisplay_latency ();
-	Gtk::ComboBoxText period_size_combo;
+    uint32_t get_rate();
-
+    void audio_mode_changed ();
-	Gtk::ComboBoxText preset_combo;
+    void interface_changed ();
-	Gtk::ComboBoxText serverpath_combo;
+    void list_devices ();
-	Gtk::ComboBoxText driver_combo;
-	Gtk::ComboBoxText interface_combo;
-	Gtk::ComboBoxText timeout_combo;
-	Gtk::ComboBoxText dither_mode_combo;
-	Gtk::ComboBoxText audio_mode_combo;
-	Gtk::ComboBoxText input_device_combo;
-	Gtk::ComboBoxText output_device_combo;
-	Gtk::ComboBoxText midi_driver_combo;
-
-	Gtk::Table basic_packer;
-	Gtk::Table options_packer;
-	Gtk::Table device_packer;
-	Gtk::HBox basic_hbox;
-	Gtk::HBox options_hbox;
-	Gtk::HBox device_hbox;
-	Gtk::Notebook notebook;
-
-	bool _used;
-
-        static bool engine_running ();
-
-	void driver_changed ();
-	void build_command_line (std::vector<std::string>&);
-
-	std::map<std::string,std::vector<std::string> > devices;
-	std::vector<std::string> backend_devs;
-	void enumerate_devices (const std::string& driver);
-
-#ifdef __APPLE__
-	std::vector<std::string> enumerate_coreaudio_devices ();
-#else
-	std::vector<std::string> enumerate_alsa_devices ();
-	std::vector<std::string> enumerate_oss_devices ();
-	std::vector<std::string> enumerate_netjack_devices ();
-	std::vector<std::string> enumerate_freebob_devices ();
-	std::vector<std::string> enumerate_ffado_devices ();
-	std::vector<std::string> enumerate_dummy_devices ();
-#endif
-
-	void redisplay_latency ();
-	uint32_t get_rate();
-	void audio_mode_changed ();
-	std::vector<std::string> server_strings;
-	void find_jack_servers (std::vector<std::string>&);
-	std::string get_device_name (const std::string& driver, const std::string& human_readable_name);
 };
 
 #endif /* __gtk2_ardour_engine_dialog_h__ */

libs/ardour/ardour/audio_backend.h

@@ -68,6 +68,33 @@ class AudioBackend {
 
     /* Discovering devices and parameters */
 
+    /** Return true if this backend requires the selection of a "driver"
+     * before any device can be selected. Return false otherwise.
+     *
+     * Intended mainly to differentiate between meta-APIs like JACK
+     * which can still expose different backends (such as ALSA or CoreAudio 
+     * or FFADO or netjack) and those like ASIO or CoreAudio which
+     * do not.
+     */
+    virtual bool requires_driver_selection() const { return false; }
+
+    /** If the return value of requires_driver_selection() is true,
+     * then this function can return the list of known driver names.
+     *
+     * If the return value of requires_driver_selection() is false,
+     * then this function should not be called. If it is called
+     * its return value is an empty vector of strings.
+     */
+    virtual std::vector<std::string> enumerate_drivers() const { return std::vector<std::string>(); }
+
+    /** Returns zero if the backend can successfully use @param name as the
+     * driver, non-zero otherwise.
+     *
+     * Should not be used unless the backend returns true from
+     * requires_driver_selection()
+     */
+    virtual int set_driver (const std::string& /*drivername*/) { return 0; }
+
     /** Returns a collection of strings identifying devices known
      * to this backend. Any of these strings may be used to identify a
      * device in other calls to the backend, though any of them may become
@@ -358,8 +385,8 @@ struct AudioBackendInfo {
      * configured and does not need (re)configuration in order
      * to be usable. Return false otherwise.
      *
-     * Note that this may return true if (re)configuration is possible,
+     * Note that this may return true if (re)configuration, even though
-     * but not required. 
+     * not currently required, is still possible.
      */
     bool (*already_configured)();
 };

libs/ardour/ardour/audioengine.h

@@ -74,7 +74,8 @@ public:
     int discover_backends();
     std::vector<const AudioBackendInfo*> available_backends() const;
     std::string current_backend_name () const;
-    int set_backend (const std::string&, const std::string& arg1, const std::string& arg2);
+    boost::shared_ptr<AudioBackend> set_backend (const std::string&, const std::string& arg1, const std::string& arg2);
+    boost::shared_ptr<AudioBackend> current_backend() const { return _backend; }
     bool setup_required () const;
 
     ProcessThread* main_thread() const { return _main_thread; }
@@ -172,13 +173,6 @@ public:
     PBD::Signal0<void> Running;
     PBD::Signal0<void> Stopped;
 
-    /* these two are emitted as we create backends that
-       can actually be used to do stuff (e.g. register ports)
-    */
-    
-    PBD::Signal0<void> BackendAvailable;
-    PBD::Signal0<void> BackendRemoved;
-    
     static AudioEngine* instance() { return _instance; }
     static void destroy();
     void died ();

libs/ardour/ardour/jack_audiobackend.h

@@ -49,7 +49,12 @@ class JACKAudioBackend : public AudioBackend {
     bool connected() const;
     bool is_realtime () const;
 
+    bool requires_driver_selection() const;
+    std::vector<std::string> enumerate_drivers () const;
+    int set_driver (const std::string&);
+
     std::vector<std::string> enumerate_devices () const;
+
     std::vector<float> available_sample_rates (const std::string& device) const;
     std::vector<uint32_t> available_buffer_sizes (const std::string& device) const;
     uint32_t available_input_channel_count (const std::string& device) const;
@@ -151,6 +156,7 @@ class JACKAudioBackend : public AudioBackend {
 
     /* pffooo */
 
+    std::string  _target_driver;
     std::string  _target_device;
     float        _target_sample_rate;
     uint32_t     _target_buffer_size;

libs/ardour/audioengine.cc

@@ -561,18 +561,16 @@ AudioEngine::drop_backend ()
 	if (_backend) {
 		_backend->stop ();
 		_backend.reset ();
-
-		BackendRemoved(); /* EMIT SIGNAL */
 	}
 }
 
-int
+boost::shared_ptr<AudioBackend>
 AudioEngine::set_backend (const std::string& name, const std::string& arg1, const std::string& arg2)
 {
 	BackendMap::iterator b = _backends.find (name);
 
 	if (b == _backends.end()) {
-		return -1;
+		return boost::shared_ptr<AudioBackend>();
 	}
 
 	drop_backend ();
@@ -590,12 +588,10 @@ AudioEngine::set_backend (const std::string& name, const std::string& arg1, cons
 
 	} catch (exception& e) {
 		error << string_compose (_("Could not create backend for %1: %2"), name, e.what()) << endmsg;
-		return -1;
+		return boost::shared_ptr<AudioBackend>();
 	}
 
-	BackendAvailable (); /* EMIT SIGNAL */
+	return _backend;
-
-	return 0;
 }
 
 /* BACKEND PROXY WRAPPERS */

libs/ardour/jack_api.cc

@@ -90,16 +90,13 @@ extern "C" {
 	 * must be non-mangled.
 	 */
 
-	using namespace ARDOUR;
+	ARDOUR::AudioBackendInfo descriptor = {
-
-	AudioBackendInfo descriptor = {
 		"JACK",
 		instantiate,
 		deinstantiate,
 		backend_factory,
 		portengine_factory,
-		already_configured
+		already_configured,
 	};
-
 }
 

libs/ardour/jack_audiobackend.cc

@@ -88,11 +88,31 @@ JACKAudioBackend::is_realtime () const
 	return jack_is_realtime (_priv_jack);
 }
 
+bool
+JACKAudioBackend::requires_driver_selection() const
+{
+	return true;
+}
+
+vector<string>
+JACKAudioBackend::enumerate_drivers () const
+{
+	vector<string> s;
+	get_jack_audio_driver_names (s);
+	return s;
+}
+
+int
+JACKAudioBackend::set_driver (const std::string& name)
+{
+	_target_driver = name;
+	return 0;
+}
+
 vector<string>
 JACKAudioBackend::enumerate_devices () const
 {
-	vector<string> devices;
+	return get_jack_device_names_for_audio_driver (_target_driver);
-	return devices;
 }
 
 vector<float>