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/*
* Copyright (c) 2022 Teddy Wing
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at https://mozilla.org/MPL/2.0/.
*/
// Version: 0.1.0
#include "SSVLSystemAlertVolume.h"
// This property appears to be private, as it isn't defined in Apple's MacOSX
// SDK framework headers.
//
// The value comes from the Sound preference pane. Disassembling the
// `/System/Library/PreferencePanes/Sound.prefPane/Contents/MacOS/Sound` binary
// shows that functions accessing the system alert volume do so via the
// '0x7373766c' property. Converting that to a FourCharCode yields 'ssvl'.
const AudioServicesPropertyID SSVLAudioServicesPropertySystemAlertVolume = 'ssvl';
OSStatus SSVLGetSystemVolume(Float32 *volume) {
UInt32 volume_size = sizeof(*volume);
OSStatus result = AudioServicesGetProperty(
SSVLAudioServicesPropertySystemAlertVolume,
0,
NULL,
&volume_size,
volume
);
if (*volume != 0) {
*volume = log(*volume) + 1.0;
}
else {
*volume = 0;
}
return result;
}
OSStatus SSVLSetSystemVolume(Float32 volume) {
volume = exp(volume - 1.0);
return AudioServicesSetProperty(
SSVLAudioServicesPropertySystemAlertVolume,
0,
NULL,
sizeof(volume),
&volume
);
}
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