BACKENDS: Modify the null mixer manager to not require SDL

backends/mixer/null/null-mixer.cpp

@@ -0,0 +1,67 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#include "backends/mixer/null/null-mixer.h"
+#include "common/savefile.h"
+
+NullMixerManager::NullMixerManager() : MixerManager() {
+	_outputRate = 22050;
+	_callsCounter = 0;
+	_callbackPeriod = 10;
+	_samples = 8192;
+	while (_samples * 16 > _outputRate * 2)
+		_samples >>= 1;
+	_samplesBuf = new uint8[_samples * 4];
+}
+
+NullMixerManager::~NullMixerManager() {
+	delete _samplesBuf;
+}
+
+void NullMixerManager::init() {
+	_mixer = new Audio::MixerImpl(_outputRate);
+	assert(_mixer);
+	_mixer->setReady(true);
+}
+
+void NullMixerManager::suspendAudio() {
+	_audioSuspended = true;
+}
+
+int NullMixerManager::resumeAudio() {
+	if (!_audioSuspended) {
+		return -2;
+	}
+	_audioSuspended = false;
+	return 0;
+}
+
+void NullMixerManager::update() {
+	if (_audioSuspended) {
+		return;
+	}
+	_callsCounter++;
+	if ((_callsCounter % _callbackPeriod) == 0) {
+		assert(_mixer);
+		_mixer->mixCallback(_samplesBuf, _samples);
+	}
+}