Remove null audio source and fix crash on exit

src/openrct2-ui/audio/AudioChannel.cpp

@@ -232,8 +232,7 @@ namespace OpenRCT2::Audio
         [[nodiscard]] AudioFormat GetFormat() const override
         {
             AudioFormat result = {};
-            // The second check is there because NullAudioSource does not implement GetFormat. Avoid calling it.
-            if (_source != nullptr && _source->GetLength() > 0)
+            if (_source != nullptr)
             {
                 result = _source->GetFormat();
             }

src/openrct2-ui/audio/AudioContext.h

@@ -50,7 +50,6 @@ namespace OpenRCT2::Audio
 
     struct ISDLAudioSource : public IAudioSource
     {
-        [[nodiscard]] virtual bool IsReleased() const abstract;
         [[nodiscard]] virtual AudioFormat GetFormat() const abstract;
     };
 

src/openrct2-ui/audio/AudioMixer.cpp

@@ -17,15 +17,9 @@
 
 using namespace OpenRCT2::Audio;
 
-AudioMixer::AudioMixer()
-{
-    _nullSource = AudioSource::CreateNull();
-}
-
 AudioMixer::~AudioMixer()
 {
     Close();
-    delete _nullSource;
 }
 
 void AudioMixer::Init(const char* device)
@@ -153,7 +147,9 @@ void AudioMixer::GetNextAudioChunk(uint8_t* dst, size_t length)
     while (it != _channels.end())
     {
         auto channel = *it;
-        if ((channel->IsDone() && channel->DeleteOnDone()) || channel->IsStopping())
+        auto channelSource = channel->GetSource();
+        auto channelSourceReleased = channelSource == nullptr || channelSource->IsReleased();
+        if (channelSourceReleased || (channel->IsDone() && channel->DeleteOnDone()) || channel->IsStopping())
         {
             delete channel;
             it = _channels.erase(it);

src/openrct2-ui/audio/AudioMixer.h

@@ -29,7 +29,6 @@ namespace OpenRCT2::Audio
     {
     private:
         std::vector<std::unique_ptr<ISDLAudioSource>> _sources;
-        IAudioSource* _nullSource = nullptr;
 
         SDL_AudioDeviceID _deviceId = 0;
         AudioFormat _format = {};
@@ -47,7 +46,6 @@ namespace OpenRCT2::Audio
         std::mutex _mutex;
 
     public:
-        AudioMixer();
         ~AudioMixer() override;
         void Init(const char* device) override;
         void Close() override;

src/openrct2/audio/AudioSource.h

@@ -22,12 +22,8 @@ namespace OpenRCT2::Audio
         virtual ~IAudioSource() = default;
 
         virtual void Release() abstract;
+        virtual bool IsReleased() const abstract;
         virtual uint64_t GetLength() const abstract;
         virtual size_t Read(void* dst, uint64_t offset, size_t len) abstract;
     };
-
-    namespace AudioSource
-    {
-        IAudioSource* CreateNull();
-    }
 } // namespace OpenRCT2::Audio

src/openrct2/audio/NullAudioSource.cpp

@@ -1,40 +0,0 @@
-/*****************************************************************************
- * Copyright (c) 2014-2020 OpenRCT2 developers
- *
- * For a complete list of all authors, please refer to contributors.md
- * Interested in contributing? Visit https://github.com/OpenRCT2/OpenRCT2
- *
- * OpenRCT2 is licensed under the GNU General Public License version 3.
- *****************************************************************************/
-
-#include "AudioSource.h"
-#include "audio.h"
-
-namespace OpenRCT2::Audio
-{
-    /**
-     * An audio source representing silence.
-     */
-    class NullAudioSource : public IAudioSource
-    {
-    public:
-        void Release() override
-        {
-        }
-
-        uint64_t GetLength() const override
-        {
-            return 0;
-        }
-
-        size_t Read([[maybe_unused]] void* dst, [[maybe_unused]] uint64_t offset, [[maybe_unused]] size_t len) override
-        {
-            return 0;
-        }
-    };
-
-    IAudioSource* AudioSource::CreateNull()
-    {
-        return new NullAudioSource();
-    }
-} // namespace OpenRCT2::Audio

src/openrct2/libopenrct2.vcxproj

@@ -625,7 +625,6 @@
     <ClCompile Include="audio\Audio.cpp" />
     <ClCompile Include="audio\AudioMixer.cpp" />
     <ClCompile Include="audio\DummyAudioContext.cpp" />
-    <ClCompile Include="audio\NullAudioSource.cpp" />
     <ClCompile Include="Cheats.cpp" />
     <ClCompile Include="CmdlineSprite.cpp" />
     <ClCompile Include="cmdline\BenchGfxCommmands.cpp" />