Add enums to AudioBackend class for getting standard error and device name strings

These could also be used for return values but are initially intended for
shared translations of error messages between backends. Ideally IMO translation
should occur in the GUI(as there may be more than one) in response to these(or
similar) error codes but that would take agreement and a fair bit of
refactoring. As it is there are errors that occur in the backends that users
will want to know about this at least allows consistent translations to be
shared between backends.

libs/ardour/ardour/audio_backend.h

@@ -86,6 +86,43 @@ class LIBARDOUR_API AudioBackend : public PortEngine {
     AudioBackend (AudioEngine& e, AudioBackendInfo& i) : PortEngine (e), _info (i), engine (e) {}
     virtual ~AudioBackend () {}
     
+	enum ErrorCode {
+		NoError = 0,
+		BackendInitializationError = -64,
+		BackendDeinitializationError,
+		AudioDeviceOpenError,
+		AudioDeviceCloseError,
+		AudioDeviceNotAvailableError,
+		AudioDeviceNotConnectedError,
+		AudioDeviceReservationError,
+		AudioDeviceIOError,
+		MidiDeviceOpenError,
+		MidiDeviceCloseError,
+		MidiDeviceNotAvailableError,
+		MidiDeviceNotConnectedError,
+		MidiDeviceIOError,
+		SampleRateNotSupportedError,
+		RequestedInputLatencyNotSupportedError,
+		RequestedOutputLatencyNotSupportedError,
+		PeriodSizeNotSupportedError,
+		PeriodCountNotSupportedError,
+		DeviceConfigurationNotSupportedError,
+		InputChannelCountNotSupportedError,
+		OutputChannelCountNotSupportedError,
+		AquireRealtimePermissionError,
+		SettingAudioThreadPriorityError,
+		SettingMIDIThreadPriorityError
+	};
+
+	static std::string get_error_string (ErrorCode);
+
+	enum StandardDeviceName {
+		DeviceNone,
+		DeviceDefault
+	};
+
+	static std::string get_standard_device_name (StandardDeviceName);
+
     /** Return the AudioBackendInfo object from which this backend
 	was constructed.
     */

libs/ardour/audio_backend.cc

@@ -0,0 +1,96 @@
+/*
+    Copyright (C) 2015 Tim Mayberry
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program; if not, write to the Free Software
+    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+
+#include "ardour/audio_backend.h"
+
+#include "i18n.h"
+
+namespace ARDOUR {
+
+std::string
+AudioBackend::get_error_string (ErrorCode error_code)
+{
+	switch (error_code) {
+	case NoError: // to stop compiler warning
+		return _("No Error occurred");
+	case BackendInitializationError:
+		return _("Failed to initialize audio backend");
+	case BackendDeinitializationError:
+		return _("Failed to deinitialize audio backend");
+	case AudioDeviceOpenError:
+		return _("Failed to open audio device");
+	case AudioDeviceCloseError:
+		return _("Failed to close audio device");
+	case AudioDeviceNotAvailableError:
+		return _("Audio device unavailable");
+	case AudioDeviceNotConnectedError:
+		return _("Audio device not connected");
+	case AudioDeviceReservationError:
+		return _("Failed to request and reserve audio device");
+	case AudioDeviceIOError:
+		return _("Audio device Input/Output error");
+	case MidiDeviceOpenError:
+		return _("Failed to open MIDI device");
+	case MidiDeviceCloseError:
+		return _("Failed to close MIDI device");
+	case MidiDeviceNotAvailableError:
+		return _("MIDI device unavailable");
+	case MidiDeviceNotConnectedError:
+		return _("MIDI device not connected");
+	case MidiDeviceIOError:
+		return _("MIDI device Input/Output error");
+	case SampleRateNotSupportedError:
+		return _("Sample rate is not supported");
+	case RequestedInputLatencyNotSupportedError:
+		return _("Requested input latency is not supported");
+	case RequestedOutputLatencyNotSupportedError:
+		return _("Requested output latency is not supported");
+	case PeriodSizeNotSupportedError:
+		return _("Period size is not supported");
+	case PeriodCountNotSupportedError:
+		return _("Period count is not supported");
+	case DeviceConfigurationNotSupportedError:
+		return _("Device configuration not supported");
+	case InputChannelCountNotSupportedError:
+		return _("Input channel count configuration not supported");
+	case OutputChannelCountNotSupportedError:
+		return _("Output channel count configuration not supported");
+	case AquireRealtimePermissionError:
+		return _("Unable to aquire realtime permissions");
+	case SettingAudioThreadPriorityError:
+		return _("Setting audio device thread priorities failed");
+	case SettingMIDIThreadPriorityError:
+		return _("Setting MIDI device thread priorities failed");
+	}
+	return std::string();
+}
+
+std::string
+AudioBackend::get_standard_device_name (StandardDeviceName device_name)
+{
+	switch (device_name) {
+	case DeviceNone:
+		return _("None");
+	case DeviceDefault:
+		return _("Default");
+	}
+	return std::string();
+}
+
+} // namespace ARDOUR

libs/ardour/wscript

@@ -22,6 +22,7 @@ libardour_sources = [
         'amp.cc',
         'analyser.cc',
         'async_midi_port.cc',
+        'audio_backend.cc',
         'audio_buffer.cc',
         'audio_diskstream.cc',
         'audio_library.cc',