Get and set system alert volume

Extract my research code from Mass-menu.

1 files changed, 62 insertions, 0 deletions

diff --git a/system_alert_volume.c b/system_alert_volume.c
new file mode 100644
index 0000000..c136a7b
--- /dev/null
+++ b/system_alert_volume.c
@@ -0,0 +1,62 @@
+#include <AudioToolbox/AudioToolbox.h>
+
+const AudioServicesPropertyID kAudioServicesPropertySystemAlertVolume = 'ssvl';
+
+OSStatus system_volume_get(Float32 *volume) {
+	UInt32 volume_size = sizeof(*volume);
+
+	OSStatus result = AudioServicesGetProperty(
+		kAudioServicesPropertySystemAlertVolume,
+		0,
+		NULL,
+		&volume_size,
+		volume
+	);
+
+	// TODO: Sound PrefPane: If result != noErr, return 0.5?
+
+	if (*volume != 0) {
+		*volume = log(*volume) + 1.0;
+	}
+	else {
+		*volume = 0;
+	}
+
+	return result;
+}
+
+OSStatus system_volume_set(Float32 volume) {
+	volume = exp(volume - 1.0);
+
+	return AudioServicesSetProperty(
+		kAudioServicesPropertySystemAlertVolume,
+		0,
+		NULL,
+		sizeof(volume),
+		&volume
+	);
+}
+
+int main() {
+	OSStatus result;
+
+	Float32 volume;
+
+	result = system_volume_get(&volume);
+	if (result != noErr) {
+		printf("Error getting system volume: %d\n", result);
+		return 1;
+	}
+
+	printf("System volume: %f\n", volume);
+
+
+	Float32 new_volume = 0.5;
+	result = system_volume_set(new_volume);
+	if (result != noErr) {
+		printf("Error setting system volume: %d\n", result);
+		return 1;
+	}
+
+	printf("Set volume to: %f\n", new_volume);
+}