Reimplement method using code extracted from EngineDialog::backend_changed

EngineControl::set_driver_popdown_strings is now like the other
set_*_popdown_strings methods in that it sets the driver strings and a
default active entry and returns false if no drivers are available.

diff --git a/gtk2_ardour/engine_dialog.cc b/gtk2_ardour/engine_dialog.cc
index 82ca022035209bfc00197dfd9a7c600218b057c4..16114f257747dd449f985d57dded541313364ffb 100644 (file)
--- a/gtk2_ardour/engine_dialog.cc
+++ b/gtk2_ardour/engine_dialog.cc
@@ -843,31 +843,8 @@ EngineControl::backend_changed ()
        _midi_devices.clear();
 
        if (backend->requires_driver_selection()) {
-               vector<string> drivers = backend->enumerate_drivers();
-               driver_combo.set_sensitive (true);
-
-               if (!drivers.empty()) {
-                       {
-                               string current_driver;
-                               current_driver = backend->driver_name ();
-
-                               DEBUG_ECONTROL (string_compose ("backend->driver_name: %1", current_driver));
-
-                               // driver might not have been set yet
-                               if (current_driver == "") {
-                                       current_driver = driver_combo.get_active_text ();
-                                       if (current_driver == "")
-                                               // driver has never been set, make sure it's not blank
-                                               current_driver = drivers.front ();
-                               }
-
-                               PBD::Unwinder<uint32_t> protect_ignore_changes (ignore_changes, ignore_changes + 1);
-                               set_popdown_strings (driver_combo, drivers);
-                               DEBUG_ECONTROL (
-                                   string_compose ("driver_combo.set_active_text: %1", current_driver));
-                               driver_combo.set_active_text (current_driver);
-                       }
-
+               if (set_driver_popdown_strings ()) {
+                       driver_combo.set_sensitive (true);
                        driver_changed ();
                }
 
@@ -930,21 +907,37 @@ EngineControl::print_channel_count (Gtk::SpinButton* sb)
        return true;
 }
 
+// @return true if there are drivers available
 bool
 EngineControl::set_driver_popdown_strings ()
 {
        DEBUG_ECONTROL ("set_driver_popdown_strings");
-       string backend_name = backend_combo.get_active_text();
-       boost::shared_ptr<ARDOUR::AudioBackend> backend;
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+       vector<string> drivers = backend->enumerate_drivers();
 
-       if (!(backend = ARDOUR::AudioEngine::instance()->set_backend (backend_name, "ardour", ""))) {
-               /* eh? setting the backend failed... how ? */
-               /* A: stale config contains a backend that does not exist in current build */
+       if (drivers.empty()) {
+               // This is an error...?
                return false;
        }
 
-       vector<string> drivers = backend->enumerate_drivers();
+       string current_driver;
+       current_driver = backend->driver_name ();
+
+       DEBUG_ECONTROL (string_compose ("backend->driver_name: %1", current_driver));
+
+       // driver might not have been set yet
+       if (current_driver == "") {
+               current_driver = driver_combo.get_active_text ();
+               if (current_driver == "")
+                       // driver has never been set, make sure it's not blank
+                       current_driver = drivers.front ();
+       }
+
+       PBD::Unwinder<uint32_t> protect_ignore_changes (ignore_changes, ignore_changes + 1);
        set_popdown_strings (driver_combo, drivers);
+       DEBUG_ECONTROL (
+                       string_compose ("driver_combo.set_active_text: %1", current_driver));
+       driver_combo.set_active_text (current_driver);
        return true;
 }