tweak GUI for backends where nperiods is driver dependent.
[ardour.git] / gtk2_ardour / engine_dialog.cc
index de734ab716411c634c4705f3eff0f1bcc8965183..ef19aa871446c282c6f8c38d892c0ecb4162009a 100644 (file)
@@ -20,7 +20,6 @@
 #include <exception>
 #include <vector>
 #include <cmath>
-#include <fstream>
 #include <map>
 
 #include <boost/scoped_ptr.hpp>
@@ -86,7 +85,8 @@ EngineControl::EngineControl ()
        , ports_spinner (ports_adjustment)
        , control_app_button (_("Device Control Panel"))
        , midi_devices_button (_("Midi Device Setup"))
-       , stop_engine_button (_("Stop (Reconfigure)"))
+       , start_stop_button (_("Stop"))
+       , update_devices_button (_("Refresh Devices"))
        , lm_measure_label (_("Measure"))
        , lm_use_button (_("Use results"))
        , lm_back_button (_("Back to settings ... (ignore results)"))
@@ -99,6 +99,7 @@ EngineControl::EngineControl ()
        , _desired_sample_rate (0)
        , started_at_least_once (false)
        , queue_device_changed (false)
+       , _have_control (true)
        , block_signals(0)
 {
        using namespace Notebook_Helpers;
@@ -185,7 +186,8 @@ EngineControl::EngineControl ()
        lm_measure_button.add (lm_measure_label);
        lm_measure_button.signal_clicked().connect (sigc::mem_fun (*this, &EngineControl::latency_button_clicked));
        lm_use_button.signal_clicked().connect (sigc::mem_fun (*this, &EngineControl::use_latency_button_clicked));
-       lm_back_button_signal = lm_back_button.signal_clicked().connect (sigc::bind (sigc::mem_fun (notebook, &Gtk::Notebook::set_current_page), 0));
+       lm_back_button_signal = lm_back_button.signal_clicked().connect(
+           sigc::mem_fun(*this, &EngineControl::latency_back_button_clicked));
 
        lm_use_button.set_sensitive (false);
 
@@ -269,13 +271,17 @@ EngineControl::EngineControl ()
        control_app_button.set_can_focus(true);
        manage_control_app_sensitivity ();
 
-       stop_engine_button.signal_clicked.connect (mem_fun (*this, &EngineControl::stop_engine_button_clicked));
-       stop_engine_button.set_sensitive (false);
-       stop_engine_button.set_name ("generic button");
-       stop_engine_button.set_can_focus(true);
+       start_stop_button.signal_clicked.connect (mem_fun (*this, &EngineControl::start_stop_button_clicked));
+       start_stop_button.set_sensitive (false);
+       start_stop_button.set_name ("generic button");
+       start_stop_button.set_can_focus(true);
+
+       update_devices_button.signal_clicked.connect (mem_fun (*this, &EngineControl::update_devices_button_clicked));
+       update_devices_button.set_sensitive (false);
+       update_devices_button.set_name ("generic button");
+       update_devices_button.set_can_focus(true);
 
        cancel_button = add_button (Gtk::Stock::CLOSE, Gtk::RESPONSE_CANCEL);
-       apply_button = add_button (Gtk::Stock::APPLY, Gtk::RESPONSE_APPLY);
        ok_button = add_button (Gtk::Stock::OK, Gtk::RESPONSE_OK);
 
        /* Pick up any existing audio setup configuration, if appropriate */
@@ -315,6 +321,8 @@ EngineControl::connect_changed_signals ()
            sigc::mem_fun (*this, &EngineControl::sample_rate_changed));
        buffer_size_combo_connection = buffer_size_combo.signal_changed ().connect (
            sigc::mem_fun (*this, &EngineControl::buffer_size_changed));
+       nperiods_combo_connection = nperiods_combo.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::nperiods_changed));
        device_combo_connection = device_combo.signal_changed ().connect (
            sigc::mem_fun (*this, &EngineControl::device_changed));
        midi_option_combo_connection = midi_option_combo.signal_changed ().connect (
@@ -344,6 +352,7 @@ EngineControl::block_changed_signals ()
                driver_combo_connection.block ();
                sample_rate_combo_connection.block ();
                buffer_size_combo_connection.block ();
+               nperiods_combo_connection.block ();
                device_combo_connection.block ();
                input_device_combo_connection.block ();
                output_device_combo_connection.block ();
@@ -364,6 +373,7 @@ EngineControl::unblock_changed_signals ()
                driver_combo_connection.unblock ();
                sample_rate_combo_connection.unblock ();
                buffer_size_combo_connection.unblock ();
+               nperiods_combo_connection.unblock ();
                device_combo_connection.unblock ();
                input_device_combo_connection.unblock ();
                output_device_combo_connection.unblock ();
@@ -402,48 +412,70 @@ EngineControl::on_show ()
        ok_button->grab_focus();
 }
 
+bool
+EngineControl::start_engine ()
+{
+       if (push_state_to_backend(true) != 0) {
+               MessageDialog msg(*this,
+                                 ARDOUR::AudioEngine::instance()->get_last_backend_error());
+               msg.run();
+               return false;
+       }
+       return true;
+}
+
+bool
+EngineControl::stop_engine (bool for_latency)
+{
+       if (ARDOUR::AudioEngine::instance()->stop(for_latency)) {
+               MessageDialog msg(*this,
+                                 ARDOUR::AudioEngine::instance()->get_last_backend_error());
+               msg.run();
+               return false;
+       }
+       return true;
+}
+
 void
 EngineControl::on_response (int response_id)
 {
        ArdourDialog::on_response (response_id);
 
        switch (response_id) {
-               case RESPONSE_APPLY:
-                       push_state_to_backend (true);
-                       break;
-               case RESPONSE_OK:
+       case RESPONSE_OK:
+               if (!start_engine()) {
+                       return;
+               } else {
+                       hide();
+               }
 #ifdef PLATFORM_WINDOWS
-                       // For some reason we don't understand, 'hide()'
-                       // needs to get called first in Windows
-                       hide ();
-
-                       // But if there's no session open, this can produce
-                       // a long gap when nothing appears to be happening.
-                       // Let's show the splash image while we're waiting.
-                       if ( !ARDOUR_COMMAND_LINE::no_splash ) {
-                               if ( ARDOUR_UI::instance() ) {
-                                       if ( !ARDOUR_UI::instance()->session_loaded ) {
-                                               ARDOUR_UI::instance()->show_splash();
-                                       }
+
+               // But if there's no session open, this can produce
+               // a long gap when nothing appears to be happening.
+               // Let's show the splash image while we're waiting.
+               if (!ARDOUR_COMMAND_LINE::no_splash) {
+                       if (ARDOUR_UI::instance()) {
+                               if (!ARDOUR_UI::instance()->session_loaded) {
+                                       ARDOUR_UI::instance()->show_splash();
                                }
                        }
-                       push_state_to_backend (true);
-                       break;
-#else
-                       push_state_to_backend (true);
-                       hide ();
-                       break;
+               }
 #endif
-               case RESPONSE_DELETE_EVENT:
-                       {
-                               GdkEventButton ev;
-                               ev.type = GDK_BUTTON_PRESS;
-                               ev.button = 1;
-                               on_delete_event ((GdkEventAny*) &ev);
-                               break;
-                       }
-               default:
-                       hide ();
+               break;
+       case RESPONSE_DELETE_EVENT: {
+               GdkEventButton ev;
+               ev.type = GDK_BUTTON_PRESS;
+               ev.button = 1;
+               on_delete_event((GdkEventAny*)&ev);
+               break;
+       }
+       case RESPONSE_CANCEL:
+               if (ARDOUR_UI::instance() && ARDOUR_UI::instance()->session_loaded) {
+                       ARDOUR_UI::instance()->check_audioengine(*this);
+               }
+       // fall through
+       default:
+               hide();
        }
 }
 
@@ -469,7 +501,8 @@ EngineControl::build_notebook ()
        basic_packer.attach (engine_status, 2, 3, 0, 1, xopt, (AttachOptions) 0);
        engine_status.show();
 
-       basic_packer.attach (stop_engine_button, 3, 4, 0, 1, xopt, xopt);
+       basic_packer.attach (start_stop_button, 3, 4, 0, 1, xopt, xopt);
+       basic_packer.attach (update_devices_button, 3, 4, 1, 2, xopt, xopt);
 
        lm_button_audio.signal_clicked.connect (sigc::mem_fun (*this, &EngineControl::calibrate_audio_latency));
        lm_button_audio.set_name ("generic button");
@@ -543,9 +576,18 @@ EngineControl::build_full_control_notebook ()
        buffer_size_duration_label.set_alignment (0.0); /* left-align */
        basic_packer.attach (buffer_size_duration_label, 2, 3, row, row+1, SHRINK, (AttachOptions) 0);
 
-       /* button spans 2 rows */
+       int ctrl_btn_span = 1;
+       if (backend->can_set_period_size ()) {
+               row++;
+               label = manage (left_aligned_label (_("Periods:")));
+               basic_packer.attach (*label, 0, 1, row, row + 1, xopt, (AttachOptions) 0);
+               basic_packer.attach (nperiods_combo, 1, 2, row, row + 1, xopt, (AttachOptions) 0);
+               ++ctrl_btn_span;
+       }
+
+       /* button spans 2 or 3 rows */
 
-       basic_packer.attach (control_app_button, 3, 4, row-1, row+1, xopt, xopt);
+       basic_packer.attach (control_app_button, 3, 4, row - ctrl_btn_span, row + 1, xopt, xopt);
        row++;
 
        input_channels.set_name ("InputChannels");
@@ -560,7 +602,7 @@ EngineControl::build_full_control_notebook ()
                basic_packer.attach (input_channels, 1, 2, row, row+1, xopt, (AttachOptions) 0);
                ++row;
        }
-       
+
        output_channels.set_name ("OutputChannels");
        output_channels.set_flags (Gtk::CAN_FOCUS);
        output_channels.set_digits (0);
@@ -573,7 +615,7 @@ EngineControl::build_full_control_notebook ()
                basic_packer.attach (output_channels, 1, 2, row, row+1, xopt, (AttachOptions) 0);
                ++row;
        }
-       
+
        input_latency.set_name ("InputLatency");
        input_latency.set_flags (Gtk::CAN_FOCUS);
        input_latency.set_digits (0);
@@ -607,7 +649,13 @@ EngineControl::build_full_control_notebook ()
        label = manage (left_aligned_label (_("MIDI System:")));
        basic_packer.attach (*label, 0, 1, row, row + 1, xopt, (AttachOptions) 0);
        basic_packer.attach (midi_option_combo, 1, 2, row, row + 1, SHRINK, (AttachOptions) 0);
+#if ! defined __APPLE__  && ! defined PLATFORM_WINDOWS // => linux, YAY
+       /* Currently the only backend with dedicated Midi setup is ALSA.
+        * lot of people complain that this is greyed out
+        * "I can't use MIDI, the setup is greyed out"
+        */
        basic_packer.attach (midi_devices_button, 3, 4, row, row+1, xopt, xopt);
+#endif
        row++;
 }
 
@@ -692,7 +740,8 @@ EngineControl::enable_latency_tab ()
                lm_back_button_signal = lm_back_button.signal_clicked().connect (sigc::bind (sigc::mem_fun (notebook, &Gtk::Notebook::set_current_page), midi_tab));
                lm_preamble.hide ();
        } else {
-               lm_back_button_signal = lm_back_button.signal_clicked().connect (sigc::bind (sigc::mem_fun (notebook, &Gtk::Notebook::set_current_page), 0));
+               lm_back_button_signal = lm_back_button.signal_clicked().connect(
+                   sigc::mem_fun(*this, &EngineControl::latency_back_button_clicked));
                lm_preamble.show ();
        }
 
@@ -732,8 +781,7 @@ EngineControl::update_sensitivity ()
        boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
        if (!backend) {
                ok_button->set_sensitive (false);
-               apply_button->set_sensitive (false);
-               stop_engine_button.set_sensitive (false);
+               start_stop_button.set_sensitive (false);
                return;
        }
 
@@ -796,20 +844,58 @@ EngineControl::update_sensitivity ()
                valid = false;
        }
 
+       if (get_popdown_string_count (nperiods_combo) > 0) {
+               if (!ARDOUR::AudioEngine::instance()->running()) {
+                       nperiods_combo.set_sensitive (true);
+               } else {
+                       nperiods_combo.set_sensitive (false);
+               }
+       } else {
+               nperiods_combo.set_sensitive (false);
+       }
+
+       if (_have_control) {
+               start_stop_button.set_sensitive(true);
+               start_stop_button.show();
+               if (ARDOUR::AudioEngine::instance()->running()) {
+                       start_stop_button.set_text("Stop");
+                       update_devices_button.set_sensitive(false);
+               } else {
+                       if (backend->can_request_update_devices()) {
+                               update_devices_button.show();
+                       } else {
+                               update_devices_button.hide();
+                       }
+                       start_stop_button.set_text("Start");
+                       update_devices_button.set_sensitive(true);
+               }
+       } else {
+               update_devices_button.set_sensitive(false);
+               update_devices_button.hide();
+               start_stop_button.set_sensitive(false);
+               start_stop_button.hide();
+       }
+
        if (ARDOUR::AudioEngine::instance()->running() && _have_control) {
-               stop_engine_button.set_sensitive (true);
-               stop_engine_button.show ();
+               input_device_combo.set_sensitive (false);
+               output_device_combo.set_sensitive (false);
+               device_combo.set_sensitive (false);
+               driver_combo.set_sensitive (false);
        } else {
-               stop_engine_button.set_sensitive (false);
-               stop_engine_button.hide ();
+               input_device_combo.set_sensitive (true);
+               output_device_combo.set_sensitive (true);
+               device_combo.set_sensitive (true);
+               if (backend->requires_driver_selection() && get_popdown_string_count(driver_combo) > 0) {
+                       driver_combo.set_sensitive (true);
+               } else {
+                       driver_combo.set_sensitive (false);
+               }
        }
 
        if (valid || !_have_control) {
                ok_button->set_sensitive (true);
-               apply_button->set_sensitive (true);
        } else {
                ok_button->set_sensitive (false);
-               apply_button->set_sensitive (false);
        }
 }
 
@@ -914,7 +1000,7 @@ EngineControl::backend_changed ()
        string backend_name = backend_combo.get_active_text();
        boost::shared_ptr<ARDOUR::AudioBackend> backend;
 
-       if (!(backend = ARDOUR::AudioEngine::instance()->set_backend (backend_name, "ardour", ""))) {
+       if (!(backend = ARDOUR::AudioEngine::instance()->set_backend (backend_name, downcase (std::string(PROGRAM_NAME)), ""))) {
                /* eh? setting the backend failed... how ? */
                /* A: stale config contains a backend that does not exist in current build */
                return;
@@ -930,12 +1016,9 @@ EngineControl::backend_changed ()
 
        if (backend->requires_driver_selection()) {
                if (set_driver_popdown_strings ()) {
-                       driver_combo.set_sensitive (true);
                        driver_changed ();
                }
-
        } else {
-               driver_combo.set_sensitive (false);
                /* this will change the device text which will cause a call to
                 * device changed which will set up parameters
                 */
@@ -956,6 +1039,20 @@ EngineControl::backend_changed ()
         */
        engine_stopped (); // set "active/inactive"
 
+       if (!_have_control) {
+               // set settings from backend that we do have control over
+               set_active_text_if_present (buffer_size_combo, bufsize_as_string (backend->buffer_size()));
+       }
+
+       if (_have_control && !ignore_changes) {
+               // set driver & devices
+               State state = get_matching_state (backend_combo.get_active_text());
+               if (state) {
+                       PBD::Unwinder<uint32_t> protect_ignore_changes (ignore_changes, ignore_changes + 1);
+                       set_current_state (state);
+               }
+       }
+
        if (!ignore_changes) {
                maybe_display_saved_state ();
        }
@@ -987,7 +1084,7 @@ EngineControl::print_channel_count (Gtk::SpinButton* sb)
        if (ARDOUR::Profile->get_mixbus()) {
                return true;
        }
-       
+
        uint32_t cnt = (uint32_t) sb->get_value();
        if (cnt == 0) {
                sb->set_text (_("all available channels"));
@@ -1029,6 +1126,46 @@ EngineControl::set_driver_popdown_strings ()
        return true;
 }
 
+std::string
+EngineControl::get_default_device(const string& current_device_name,
+                                  const vector<string>& available_devices)
+{
+       // If the current device is available, use it as default
+       if (std::find (available_devices.begin (),
+                      available_devices.end (),
+                      current_device_name) != available_devices.end ()) {
+
+               return current_device_name;
+       }
+
+       using namespace ARDOUR;
+
+       string default_device_name =
+           AudioBackend::get_standard_device_name(AudioBackend::DeviceDefault);
+
+       vector<string>::const_iterator i;
+
+       // If there is a "Default" device available, use it
+       for (i = available_devices.begin(); i != available_devices.end(); ++i) {
+               if (*i == default_device_name) {
+                       return *i;
+               }
+       }
+
+       string none_device_name =
+           AudioBackend::get_standard_device_name(AudioBackend::DeviceNone);
+
+       // Use the first device that isn't "None"
+       for (i = available_devices.begin(); i != available_devices.end(); ++i) {
+               if (*i != none_device_name) {
+                       return *i;
+               }
+       }
+
+       // Use "None" if there are no other available
+       return available_devices.front();
+}
+
 // @return true if there are devices available
 bool
 EngineControl::set_device_popdown_strings ()
@@ -1056,23 +1193,15 @@ EngineControl::set_device_popdown_strings ()
                return false;
        }
 
-       string current_device = backend->device_name ();
-
-       // Make sure that backend->device_name () is a valid
-       // device, the backend may not return a valid device if it hasn't
-       // been set yet.
-       if (std::find (available_devices.begin (),
-                      available_devices.end (),
-                      current_device) == available_devices.end ()) {
+       set_popdown_strings (device_combo, available_devices);
 
-               current_device = available_devices.front ();
-       }
+       std::string default_device =
+           get_default_device(backend->device_name(), available_devices);
 
-       set_popdown_strings (device_combo, available_devices);
        DEBUG_ECONTROL (
-           string_compose ("set device_combo active text: %1", current_device));
+           string_compose ("set device_combo active text: %1", default_device));
 
-       device_combo.set_active_text (current_device);
+       device_combo.set_active_text(default_device);
        return true;
 }
 
@@ -1094,23 +1223,14 @@ EngineControl::set_input_device_popdown_strings ()
                return false;
        }
 
-       string current_device = backend->input_device_name ();
-
-       // Make sure that backend->input_device_name () is a valid
-       // device, the backend may not return a valid device if it hasn't
-       // been set yet.
-       if (std::find (available_devices.begin (),
-                      available_devices.end (),
-                      current_device) == available_devices.end ()) {
-
-               current_device = available_devices.front ();
-       }
-
        set_popdown_strings (input_device_combo, available_devices);
 
+       std::string default_device =
+           get_default_device(backend->input_device_name(), available_devices);
+
        DEBUG_ECONTROL (
-           string_compose ("set input_device_combo active text: %1", current_device));
-       input_device_combo.set_active_text (current_device);
+           string_compose ("set input_device_combo active text: %1", default_device));
+       input_device_combo.set_active_text(default_device);
        return true;
 }
 
@@ -1132,23 +1252,14 @@ EngineControl::set_output_device_popdown_strings ()
                return false;
        }
 
-       string current_device = backend->output_device_name ();
-
-       // Make sure that backend->output_device_name () is a valid
-       // device, the backend may not return a valid device if it hasn't
-       // been set yet.
-       if (std::find (available_devices.begin (),
-                      available_devices.end (),
-                      current_device) == available_devices.end ()) {
-
-               current_device = available_devices.front ();
-       }
-
        set_popdown_strings (output_device_combo, available_devices);
 
+       std::string default_device =
+           get_default_device(backend->output_device_name(), available_devices);
+
        DEBUG_ECONTROL (
-           string_compose ("set output_device_combo active text: %1", current_device));
-       output_device_combo.set_active_text (current_device);
+           string_compose ("set output_device_combo active text: %1", default_device));
+       output_device_combo.set_active_text(default_device);
        return true;
 }
 
@@ -1191,6 +1302,8 @@ EngineControl::driver_changed ()
        backend->set_driver (driver_combo.get_active_text());
        list_devices ();
 
+       // TODO load LRU device(s) for backend + driver combo
+
        if (!ignore_changes) {
                maybe_display_saved_state ();
        }
@@ -1204,7 +1317,7 @@ EngineControl::get_sample_rates_for_all_devices ()
        vector<float> all_rates;
 
        if (backend->use_separate_input_and_output_devices ()) {
-               all_rates = backend->available_sample_rates (get_input_device_name (), get_output_device_name ());
+               all_rates = backend->available_sample_rates2 (get_input_device_name (), get_output_device_name ());
        } else {
                all_rates = backend->available_sample_rates (get_device_name ());
        }
@@ -1276,7 +1389,7 @@ EngineControl::get_buffer_sizes_for_all_devices ()
        vector<uint32_t> all_sizes;
 
        if (backend->use_separate_input_and_output_devices ()) {
-               all_sizes = backend->available_buffer_sizes (get_input_device_name (), get_output_device_name ());
+               all_sizes = backend->available_buffer_sizes2 (get_input_device_name (), get_output_device_name ());
        } else {
                all_sizes = backend->available_buffer_sizes (get_device_name ());
        }
@@ -1319,28 +1432,64 @@ EngineControl::set_buffersize_popdown_strings ()
                s.push_back (bufsize_as_string (*x));
        }
 
+       uint32_t previous_size = 0;
+       if (!buffer_size_combo.get_active_text().empty()) {
+               previous_size = get_buffer_size ();
+       }
+
        set_popdown_strings (buffer_size_combo, s);
 
        if (!s.empty()) {
-               buffer_size_combo.set_active_text (s.front());
 
-               uint32_t period = backend->buffer_size();
-               if (0 == period && backend->use_separate_input_and_output_devices ()) {
-                       period = backend->default_buffer_size (get_input_device_name ());
-               }
-               if (0 == period && backend->use_separate_input_and_output_devices ()) {
-                       period = backend->default_buffer_size (get_output_device_name ());
-               }
-               if (0 == period && !backend->use_separate_input_and_output_devices ()) {
-                       period = backend->default_buffer_size (get_device_name ());
-               }
+               if (std::find(bs.begin(), bs.end(), previous_size) != bs.end()) {
+                       buffer_size_combo.set_active_text(bufsize_as_string(previous_size));
+               } else {
 
-               set_active_text_if_present (buffer_size_combo, bufsize_as_string (period));
+                       buffer_size_combo.set_active_text(s.front());
+
+                       uint32_t period = backend->buffer_size();
+                       if (0 == period && backend->use_separate_input_and_output_devices()) {
+                               period = backend->default_buffer_size(get_input_device_name());
+                       }
+                       if (0 == period && backend->use_separate_input_and_output_devices()) {
+                               period = backend->default_buffer_size(get_output_device_name());
+                       }
+                       if (0 == period && !backend->use_separate_input_and_output_devices()) {
+                               period = backend->default_buffer_size(get_device_name());
+                       }
+
+                       set_active_text_if_present(buffer_size_combo, bufsize_as_string(period));
+               }
                show_buffer_duration ();
        }
        update_sensitivity ();
 }
 
+void
+EngineControl::set_nperiods_popdown_strings ()
+{
+       DEBUG_ECONTROL ("set_nperiods_popdown_strings");
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+       vector<uint32_t> np;
+       vector<string> s;
+
+       if (backend->can_set_period_size()) {
+               np = backend->available_period_sizes (get_driver());
+       }
+
+       for (vector<uint32_t>::const_iterator x = np.begin(); x != np.end(); ++x) {
+               s.push_back (nperiods_as_string (*x));
+       }
+
+       set_popdown_strings (nperiods_combo, s);
+
+       if (!s.empty()) {
+               set_active_text_if_present (nperiods_combo, nperiods_as_string (backend->period_size())); // XXX 
+       }
+
+       update_sensitivity ();
+}
+
 void
 EngineControl::device_changed ()
 {
@@ -1372,7 +1521,7 @@ EngineControl::device_changed ()
                        queue_device_changed = true;
                }
        }
-       
+
        //the device name must be set FIRST so ASIO can populate buffersizes and the control panel button
        if (backend->use_separate_input_and_output_devices()) {
                backend->set_input_device_name (device_name_in);
@@ -1389,6 +1538,7 @@ EngineControl::device_changed ()
 
                set_samplerate_popdown_strings ();
                set_buffersize_popdown_strings ();
+               set_nperiods_popdown_strings ();
 
                /* TODO set min + max channel counts here */
 
@@ -1427,6 +1577,15 @@ EngineControl::bufsize_as_string (uint32_t sz)
        return buf;
 }
 
+string
+EngineControl::nperiods_as_string (uint32_t np)
+{
+       char buf[8];
+       snprintf (buf, sizeof (buf), "%u", np);
+       return buf;
+}
+
+
 void
 EngineControl::sample_rate_changed ()
 {
@@ -1446,6 +1605,13 @@ EngineControl::buffer_size_changed ()
        show_buffer_duration ();
 }
 
+void
+EngineControl::nperiods_changed ()
+{
+       DEBUG_ECONTROL ("nperiods_changed");
+       show_buffer_duration ();
+}
+
 void
 EngineControl::show_buffer_duration ()
 {
@@ -1458,17 +1624,12 @@ EngineControl::show_buffer_duration ()
        uint32_t samples = atoi (bs_text); /* will ignore trailing text */
        uint32_t rate = get_rate();
 
-       /* Developers: note the hard-coding of a double buffered model
-          in the (2 * samples) computation of latency. we always start
-          the audiobackend in this configuration.
-        */
-       /* note to jack1 developers: ardour also always starts the engine
-        * in async mode (no jack2 --sync option) which adds an extra cycle
-        * of latency with jack2 (and *3 would be correct)
-        * The value can also be wrong if jackd is started externally..
+       /* Except for ALSA and Dummy backends, we don't know the number of periods
+        * per cycle and settings.
         *
-        * At the time of writing the ALSA backend always uses double-buffering *2,
-        * The Dummy backend *1, and who knows what ASIO really does :)
+        * jack1 vs jack2 have different default latencies since jack2 start
+        * in async-mode unless --sync is given which adds an extra cycle
+        * of latency. The value is not known if jackd is started externally..
         *
         * So just display the period size, that's also what
         * ARDOUR_UI::update_sample_rate() does for the status bar.
@@ -1525,6 +1686,17 @@ EngineControl::parameter_changed ()
 {
 }
 
+EngineControl::State
+EngineControl::get_matching_state (const string& backend)
+{
+       for (StateList::iterator i = states.begin(); i != states.end(); ++i) {
+               if ((*i)->backend == backend) {
+                       return (*i);
+               }
+       }
+       return State();
+}
+
 EngineControl::State
 EngineControl::get_matching_state (
                const string& backend,
@@ -1594,6 +1766,19 @@ bool EngineControl::equivalent_states (const EngineControl::State& state1,
        return false;
 }
 
+bool
+EngineControl::state_sort_cmp (const State &a, const State &b) {
+       if (a->active) {
+               return true;
+       }
+       else if (b->active) {
+               return false;
+       }
+       else {
+               return a->lru < b->lru;
+       }
+}
+
 EngineControl::State
 EngineControl::save_state ()
 {
@@ -1602,6 +1787,7 @@ EngineControl::save_state ()
        if (!_have_control) {
                state = get_matching_state (backend_combo.get_active_text(), string(), string());
                if (state) {
+                       state->lru = time (NULL) ;
                        return state;
                }
                state.reset(new StateStruct);
@@ -1621,6 +1807,8 @@ EngineControl::save_state ()
 
        states.push_back (state);
 
+       states.sort (state_sort_cmp);
+
        return state;
 }
 
@@ -1634,12 +1822,14 @@ EngineControl::store_state (State state)
        state->output_device = get_output_device_name ();
        state->sample_rate = get_rate ();
        state->buffer_size = get_buffer_size ();
+       state->n_periods = get_nperiods ();
        state->input_latency = get_input_latency ();
        state->output_latency = get_output_latency ();
        state->input_channels = get_input_channels ();
        state->output_channels = get_output_channels ();
        state->midi_option = get_midi_option ();
        state->midi_devices = _midi_devices;
+       state->lru = time (NULL) ;
 }
 
 void
@@ -1652,12 +1842,15 @@ EngineControl::maybe_display_saved_state ()
        State state = get_saved_state_for_currently_displayed_backend_and_device ();
 
        if (state) {
+               DEBUG_ECONTROL ("Restoring saved state");
                PBD::Unwinder<uint32_t> protect_ignore_changes (ignore_changes, ignore_changes + 1);
 
                if (!_desired_sample_rate) {
                        sample_rate_combo.set_active_text (rate_as_string (state->sample_rate));
                }
                set_active_text_if_present (buffer_size_combo, bufsize_as_string (state->buffer_size));
+
+               set_active_text_if_present (nperiods_combo, nperiods_as_string (state->n_periods));
                /* call this explicitly because we're ignoring changes to
                   the controls at this point.
                 */
@@ -1669,6 +1862,8 @@ EngineControl::maybe_display_saved_state ()
                        midi_option_combo.set_active_text (state->midi_option);
                        _midi_devices = state->midi_devices;
                }
+       } else {
+               DEBUG_ECONTROL ("Unable to find saved state for backend and devices");
        }
 }
 
@@ -1694,12 +1889,14 @@ EngineControl::get_state ()
                        node->add_property ("output-device", (*i)->output_device);
                        node->add_property ("sample-rate", (*i)->sample_rate);
                        node->add_property ("buffer-size", (*i)->buffer_size);
+                       node->add_property ("n-periods", (*i)->n_periods);
                        node->add_property ("input-latency", (*i)->input_latency);
                        node->add_property ("output-latency", (*i)->output_latency);
                        node->add_property ("input-channels", (*i)->input_channels);
                        node->add_property ("output-channels", (*i)->output_channels);
                        node->add_property ("active", (*i)->active ? "yes" : "no");
                        node->add_property ("midi-option", (*i)->midi_option);
+                       node->add_property ("lru", (*i)->active ? time (NULL) : (*i)->lru);
 
                        XMLNode* midi_devices = new XMLNode ("MIDIDevices");
                        for (std::vector<MidiDeviceSettings>::const_iterator p = (*i)->midi_devices.begin(); p != (*i)->midi_devices.end(); ++p) {
@@ -1810,6 +2007,13 @@ EngineControl::set_state (const XMLNode& root)
                        }
                        state->buffer_size = atoi (prop->value ());
 
+                       if ((prop = grandchild->property ("n-periods")) == 0) {
+                               // optional (new value in 4.5)
+                               state->n_periods = 0;
+                       } else {
+                               state->n_periods = atoi (prop->value ());
+                       }
+
                        if ((prop = grandchild->property ("input-latency")) == 0) {
                                continue;
                        }
@@ -1863,6 +2067,10 @@ EngineControl::set_state (const XMLNode& root)
                                }
                        }
 
+                       if ((prop = grandchild->property ("lru"))) {
+                               state->lru = atoi (prop->value ());
+                       }
+
 #if 1
                        /* remove accumulated duplicates (due to bug in ealier version)
                         * this can be removed again before release
@@ -1899,6 +2107,8 @@ EngineControl::set_state (const XMLNode& root)
                }
        }
 
+       states.sort (state_sort_cmp);
+
        for (StateList::const_iterator i = states.begin(); i != states.end(); ++i) {
 
                if ((*i)->active) {
@@ -1916,7 +2126,7 @@ EngineControl::set_current_state (const State& state)
        boost::shared_ptr<ARDOUR::AudioBackend> backend;
 
        if (!(backend = ARDOUR::AudioEngine::instance ()->set_backend (
-                 state->backend, "ardour", ""))) {
+                 state->backend, downcase (std::string(PROGRAM_NAME)), ""))) {
                DEBUG_ECONTROL (string_compose ("Unable to set backend to %1", state->backend));
                // this shouldn't happen as the invalid backend names should have been
                // removed from the list of states.
@@ -1927,6 +2137,13 @@ EngineControl::set_current_state (const State& state)
        // do the right thing
        backend_combo.set_active_text (state->backend);
 
+       if (!ARDOUR::AudioEngine::instance()->setup_required ()) {
+               backend_changed ();
+               // we don't have control don't restore state
+               return true;
+       }
+
+
        if (!state->driver.empty ()) {
                if (!backend->requires_driver_selection ()) {
                        DEBUG_ECONTROL ("Backend should require driver selection");
@@ -1991,6 +2208,7 @@ EngineControl::set_current_state (const State& state)
        output_device_combo.set_active_text (state->output_device);
        sample_rate_combo.set_active_text (rate_as_string (state->sample_rate));
        set_active_text_if_present (buffer_size_combo, bufsize_as_string (state->buffer_size));
+       set_active_text_if_present (nperiods_combo, nperiods_as_string (state->n_periods));
        input_latency.set_value (state->input_latency);
        output_latency.set_value (state->output_latency);
        midi_option_combo.set_active_text (state->midi_option);
@@ -2015,6 +2233,7 @@ EngineControl::push_state_to_backend (bool start)
        bool change_device = false;
        bool change_rate = false;
        bool change_bufsize = false;
+       bool change_nperiods = false;
        bool change_latency = false;
        bool change_channels = false;
        bool change_midi = false;
@@ -2059,6 +2278,11 @@ EngineControl::push_state_to_backend (bool start)
                                change_bufsize = true;
                        }
 
+                       if (backend->can_set_period_size() && get_popdown_string_count (nperiods_combo) > 0
+                                       && get_nperiods() != backend->period_size()) {
+                               change_nperiods = true;
+                       }
+
                        if (get_midi_option() != backend->midi_option()) {
                                change_midi = true;
                        }
@@ -2098,6 +2322,7 @@ EngineControl::push_state_to_backend (bool start)
                        change_channels = true;
                        change_latency = true;
                        change_midi = true;
+                       change_nperiods = backend->can_set_period_size() && get_popdown_string_count (nperiods_combo) > 0;
                }
 
        } else {
@@ -2155,7 +2380,8 @@ EngineControl::push_state_to_backend (bool start)
 
        /* determine if we need to stop the backend before changing parameters */
 
-       if (change_driver || change_device || change_channels || change_latency ||
+       if (change_driver || change_device || change_channels || change_nperiods ||
+                       (change_latency && !backend->can_change_systemic_latency_when_running ()) ||
                        (change_rate && !backend->can_change_sample_rate_when_running()) ||
                        change_midi ||
                        (change_bufsize && !backend->can_change_buffer_size_when_running())) {
@@ -2164,35 +2390,15 @@ EngineControl::push_state_to_backend (bool start)
                restart_required = false;
        }
 
-       if (was_running) {
-
-               if (!change_driver && !change_device && !change_channels && !change_latency && !change_midi) {
-                       /* no changes in any parameters that absolutely require a
-                        * restart, so check those that might be changeable without a
-                        * restart
-                        */
-
-                       if (change_rate && !backend->can_change_sample_rate_when_running()) {
-                               /* can't do this while running ... */
-                               restart_required = true;
-                       }
-
-                       if (change_bufsize && !backend->can_change_buffer_size_when_running()) {
-                               /* can't do this while running ... */
-                               restart_required = true;
-                       }
-               }
-       }
 
        if (was_running) {
                if (restart_required) {
-                       if (ARDOUR_UI::instance()->disconnect_from_engine ()) {
+                       if (ARDOUR::AudioEngine::instance()->stop()) {
                                return -1;
                        }
                }
        }
 
-
        if (change_driver && backend->set_driver (get_driver())) {
                error << string_compose (_("Cannot set driver to %1"), get_driver()) << endmsg;
                return -1;
@@ -2220,6 +2426,10 @@ EngineControl::push_state_to_backend (bool start)
                error << string_compose (_("Cannot set buffer size to %1"), get_buffer_size()) << endmsg;
                return -1;
        }
+       if (change_nperiods && backend->set_peridod_size (get_nperiods())) {
+               error << string_compose (_("Cannot set periods to %1"), get_nperiods()) << endmsg;
+               return -1;
+       }
 
        if (change_channels || get_input_channels() == 0 || get_output_channels() == 0) {
                if (backend->set_input_channels (get_input_channels())) {
@@ -2254,6 +2464,10 @@ EngineControl::push_state_to_backend (bool start)
                                } else {
                                        backend->set_midi_device_enabled ((*p)->name, false);
                                }
+                               if (backend->can_change_systemic_latency_when_running ()) {
+                                       backend->set_systemic_midi_input_latency ((*p)->name, 0);
+                                       backend->set_systemic_midi_output_latency ((*p)->name, 0);
+                               }
                                continue;
                        }
                        backend->set_midi_device_enabled ((*p)->name, (*p)->enabled);
@@ -2265,7 +2479,7 @@ EngineControl::push_state_to_backend (bool start)
        }
 
        if (start || (was_running && restart_required)) {
-               if (ARDOUR_UI::instance()->reconnect_to_engine()) {
+               if (ARDOUR::AudioEngine::instance()->start()) {
                        return -1;
                }
        }
@@ -2291,6 +2505,8 @@ EngineControl::post_push ()
                store_state(state);
        }
 
+       states.sort (state_sort_cmp);
+
        /* all off */
 
        for (StateList::iterator i = states.begin(); i != states.end(); ++i) {
@@ -2341,6 +2557,13 @@ EngineControl::get_buffer_size () const
        return samples;
 }
 
+uint32_t
+EngineControl::get_nperiods () const
+{
+       string txt = nperiods_combo.get_active_text ();
+       return atoi (txt.c_str());
+}
+
 string
 EngineControl::get_midi_option () const
 {
@@ -2390,7 +2613,7 @@ EngineControl::get_backend () const
 string
 EngineControl::get_driver () const
 {
-       if (driver_combo.get_sensitive() && driver_combo.get_parent()) {
+       if (driver_combo.get_parent()) {
                return driver_combo.get_active_text ();
        } else {
                return "";
@@ -2428,9 +2651,33 @@ EngineControl::control_app_button_clicked ()
 }
 
 void
-EngineControl::stop_engine_button_clicked ()
+EngineControl::start_stop_button_clicked ()
 {
-       ARDOUR::AudioEngine::instance()->stop ();
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+
+       if (!backend) {
+               return;
+       }
+
+       if (ARDOUR::AudioEngine::instance()->running()) {
+               ARDOUR::AudioEngine::instance()->stop ();
+       } else {
+               start_engine ();
+       }
+}
+
+void
+EngineControl::update_devices_button_clicked ()
+{
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+
+       if (!backend) {
+               return;
+       }
+
+       if (backend->update_devices()) {
+               device_list_changed ();
+       }
 }
 
 void
@@ -2468,7 +2715,6 @@ EngineControl::on_switch_page (GtkNotebookPage*, guint page_num)
        } else {
                cancel_button->set_sensitive (false);
                ok_button->set_sensitive (false);
-               apply_button->set_sensitive (false);
        }
 
        if (page_num == midi_tab) {
@@ -2480,8 +2726,7 @@ EngineControl::on_switch_page (GtkNotebookPage*, guint page_num)
                /* latency tab */
 
                if (ARDOUR::AudioEngine::instance()->running()) {
-                       // TODO - mark as 'stopped for latency
-                       ARDOUR_UI::instance()->disconnect_from_engine ();
+                       stop_engine (true);
                }
 
                {
@@ -2694,6 +2939,13 @@ EngineControl::latency_button_clicked ()
        }
 }
 
+void
+EngineControl::latency_back_button_clicked ()
+{
+       ARDOUR::AudioEngine::instance()->stop(true);
+       notebook.set_current_page(0);
+}
+
 void
 EngineControl::use_latency_button_clicked ()
 {
@@ -2723,9 +2975,8 @@ EngineControl::use_latency_button_clicked ()
 
                /* back to settings page */
                notebook.set_current_page (0);
-}
        }
-
+}
 
 bool
 EngineControl::on_delete_event (GdkEventAny* ev)
@@ -2746,11 +2997,19 @@ EngineControl::engine_running ()
        set_active_text_if_present (buffer_size_combo, bufsize_as_string (backend->buffer_size()));
        sample_rate_combo.set_active_text (rate_as_string (backend->sample_rate()));
 
+       if (backend->can_set_period_size ()) {
+               set_active_text_if_present (nperiods_combo, nperiods_as_string (backend->period_size()));
+       }
+
        connect_disconnect_button.set_label (string_compose (_("Disconnect from %1"), backend->name()));
        connect_disconnect_button.show();
 
        started_at_least_once = true;
-       engine_status.set_markup(string_compose ("<span foreground=\"green\">%1</span>", _("Running")));
+       if (_have_control) {
+               engine_status.set_markup(string_compose ("<span foreground=\"green\">%1</span>", _("Running")));
+       } else {
+               engine_status.set_markup(string_compose ("<span foreground=\"green\">%1</span>", _("Connected")));
+       }
        update_sensitivity();
 }
 
@@ -2763,7 +3022,12 @@ EngineControl::engine_stopped ()
        connect_disconnect_button.set_label (string_compose (_("Connect to %1"), backend->name()));
        connect_disconnect_button.show();
 
-       engine_status.set_markup(X_(""));
+       if (_have_control) {
+               engine_status.set_markup(string_compose ("<span foreground=\"red\">%1</span>", _("Stopped")));
+       } else {
+               engine_status.set_markup(X_(""));
+       }
+
        update_sensitivity();
 }
 
@@ -2779,9 +3043,9 @@ void
 EngineControl::connect_disconnect_click()
 {
        if (ARDOUR::AudioEngine::instance()->running()) {
-               ARDOUR_UI::instance()->disconnect_from_engine ();
+               stop_engine ();
        } else {
-               ARDOUR_UI::instance()->reconnect_to_engine ();
+               start_engine ();
        }
 }