Add API to enforce valid device selection.

3 files changed, 10 insertions, 0 deletions

diff --git a/libs/ardour/ardour/audio_backend.h b/libs/ardour/ardour/audio_backend.h
index 9a00cf281e..6523eb5081 100644
--- a/libs/ardour/ardour/audio_backend.h
+++ b/libs/ardour/ardour/audio_backend.h
@@ -202,6 +202,14 @@ class LIBARDOUR_API AudioBackend : public PortEngine {
      */
     virtual bool use_separate_input_and_output_devices () const { return false; }
 
+    /* Return true if the backend uses separate I/O devices only for the case
+     * of allowing one to be "None".
+     *
+     * ie. Input Device must match Output Device, except if either of them
+     * is get_standard_device_name (DeviceNone).
+     */
+    virtual bool match_input_output_devices_or_none () const { return false; }
+
     /** Returns a collection of DeviceStatuses identifying devices discovered
      * by this backend since the start of the process.
      *
diff --git a/libs/backends/alsa/alsa_audiobackend.h b/libs/backends/alsa/alsa_audiobackend.h
index d8dfb31725..bc2620ed9e 100644
--- a/libs/backends/alsa/alsa_audiobackend.h
+++ b/libs/backends/alsa/alsa_audiobackend.h
@@ -172,6 +172,7 @@ class AlsaAudioBackend : public AudioBackend {
 		bool is_realtime () const;
 
 		bool use_separate_input_and_output_devices () const { return true; }
+		bool match_input_output_devices_or_none () const { return true; }
 		bool can_set_period_size () const { return true; }
 
 		std::vector<DeviceStatus> enumerate_devices () const;
diff --git a/libs/backends/portaudio/portaudio_backend.h b/libs/backends/portaudio/portaudio_backend.h
index 601c3433cb..692e4c0e61 100644
--- a/libs/backends/portaudio/portaudio_backend.h
+++ b/libs/backends/portaudio/portaudio_backend.h
@@ -179,6 +179,7 @@ class PortAudioBackend : public AudioBackend {
 		bool get_use_buffered_io () { return _use_blocking_api; }
 
 		bool use_separate_input_and_output_devices () const;
+		bool match_input_output_devices_or_none () const { return true; }
 		std::vector<DeviceStatus> enumerate_devices () const;
 		std::vector<DeviceStatus> enumerate_input_devices () const;
 		std::vector<DeviceStatus> enumerate_output_devices () const;