build/android/app/CMakeLists.txt

@@ -62,8 +62,8 @@ add_library(kaliber SHARED
     ../../../src/demo/sky_quad.cc
     ../../../src/engine/animatable.cc
     ../../../src/engine/animator.cc
-    ../../../src/engine/audio/audio_driver_oboe.cc
-    ../../../src/engine/audio/audio_mixer.cc
+    ../../../src/engine/audio/audio_base.cc
+    ../../../src/engine/audio/audio_oboe.cc
     ../../../src/engine/drawable.cc
     ../../../src/engine/engine.cc
     ../../../src/engine/font.cc

build/android/app/src/main/AndroidManifest.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    android:versionCode="18"
+    android:versionCode="17"
     android:versionName="1.0.2">
 
     <application

build/linux/Makefile

@@ -95,8 +95,8 @@ $(BASE_LIB): $(BASE_OBJS)
 ENGINE_SRC := \
   $(SRC_ROOT)/engine/animatable.cc \
   $(SRC_ROOT)/engine/animator.cc \
-  $(SRC_ROOT)/engine/audio/audio_driver_alsa.cc \
-  $(SRC_ROOT)/engine/audio/audio_mixer.cc \
+  $(SRC_ROOT)/engine/audio/audio_alsa.cc \
+  $(SRC_ROOT)/engine/audio/audio_base.cc \
   $(SRC_ROOT)/engine/drawable.cc \
   $(SRC_ROOT)/engine/engine.cc \
   $(SRC_ROOT)/engine/font.cc \

src/demo/demo.cc

@@ -50,10 +50,6 @@ Demo::~Demo() {
 bool Demo::Initialize() {
   saved_data_.Load(kSaveFileName);
 
-  Engine::Get().LoadCustomShader("sky_without_nebula",
-                                 "sky_without_nebula.glsl");
-  Engine::Get().LoadCustomShader("sky", "sky.glsl");
-
   if (!font_.Load("PixelCaps!.ttf"))
     return false;
 
@@ -166,6 +162,11 @@ void Demo::Update(float delta_time) {
     UpdateGameState(delta_time);
 }
 
+void Demo::ContextLost() {
+  sky_.ContextLost();
+  enemy_.ContextLost();
+}
+
 void Demo::LostFocus() {}
 
 void Demo::GainedFocus(bool from_interstitial_ad) {

src/demo/demo.h

@@ -27,7 +27,7 @@ class Demo final : public eng::Game {
 
   void Update(float delta_time) final;
 
-  void ContextLost() final {}
+  void ContextLost() final;
 
   void LostFocus() final;
 

src/demo/enemy.cc

@@ -13,6 +13,8 @@
 #include "engine/font.h"
 #include "engine/image.h"
 #include "engine/renderer/geometry.h"
+#include "engine/renderer/shader.h"
+#include "engine/shader_source.h"
 #include "engine/sound.h"
 
 #include "demo/demo.h"
@@ -74,7 +76,8 @@ float SnapSpawnPosX(int col) {
 
 }  // namespace
 
-Enemy::Enemy() = default;
+Enemy::Enemy()
+    : chromatic_aberration_(Engine::Get().CreateRenderResource<Shader>()) {}
 
 Enemy::~Enemy() = default;
 
@@ -202,6 +205,10 @@ void Enemy::Pause(bool pause) {
   boss_animator_.PauseOrResumeAll(pause);
 }
 
+void Enemy::ContextLost() {
+  CreateShaders();
+}
+
 bool Enemy::HasTarget(DamageType damage_type) {
   DCHECK(damage_type > kDamageType_Invalid && damage_type < kDamageType_Any);
 
@@ -416,7 +423,7 @@ void Enemy::StopAllEnemyUnits(bool chromatic_aberration_effect) {
       continue;
 
     if (chromatic_aberration_effect) {
-      e.sprite.SetCustomShader("chromatic_aberration");
+      e.sprite.SetCustomShader(chromatic_aberration_.get());
       e.chromatic_aberration_active_ = true;
     }
 
@@ -1186,6 +1193,9 @@ std::unique_ptr<Image> Enemy::GetScoreImage(EnemyType enemy_type) {
 }
 
 bool Enemy::CreateRenderResources() {
+  if (!CreateShaders())
+    return false;
+
   Engine::Get().SetImageSource("skull_tex", "enemy_anims_01_frames_ok.png",
                                true);
   Engine::Get().SetImageSource("bug_tex", "enemy_anims_02_frames_ok.png", true);
@@ -1203,9 +1213,16 @@ bool Enemy::CreateRenderResources() {
         "score_tex"s + std::to_string(i),
         std::bind(&Enemy::GetScoreImage, this, (EnemyType)i), true);
 
-  Engine::Get().LoadCustomShader("chromatic_aberration",
-                                 "chromatic_aberration.glsl");
+  return true;
+}
 
+bool Enemy::CreateShaders() {
+  auto source = std::make_unique<ShaderSource>();
+  if (!source->Load("chromatic_aberration.glsl"))
+    return false;
+  chromatic_aberration_->Create(std::move(source),
+                                Engine::Get().GetQuad()->vertex_description(),
+                                Engine::Get().GetQuad()->primitive(), false);
   return true;
 }
 

src/demo/enemy.h

@@ -15,6 +15,7 @@
 
 namespace eng {
 class Image;
+class Shader;
 class Sound;
 }  // namespace eng
 
@@ -29,6 +30,8 @@ class Enemy {
 
   void Pause(bool pause);
 
+  void ContextLost();
+
   bool HasTarget(DamageType damage_type);
   base::Vector2f GetTargetPos(DamageType damage_type);
 
@@ -103,6 +106,7 @@ class Enemy {
     eng::SoundPlayer hit;
   };
 
+  std::unique_ptr<eng::Shader> chromatic_aberration_;
   float chromatic_aberration_offset_ = 0;
 
   eng::ImageQuad boss_;
@@ -165,6 +169,7 @@ class Enemy {
   std::unique_ptr<eng::Image> GetScoreImage(EnemyType enemy_type);
 
   bool CreateRenderResources();
+  bool CreateShaders();
 
   void TranslateEnemyUnit(EnemyUnit& e, const base::Vector2f& delta);
 };

src/demo/sky_quad.cc

@@ -6,12 +6,14 @@
 #include "engine/engine.h"
 #include "engine/renderer/geometry.h"
 #include "engine/renderer/shader.h"
+#include "engine/shader_source.h"
 
 using namespace base;
 using namespace eng;
 
 SkyQuad::SkyQuad()
-    : sky_offset_{
+    : shader_(Engine::Get().CreateRenderResource<Shader>()),
+      sky_offset_{
           0, Lerp(0.0f, 10.0f, Engine::Get().GetRandomGenerator().Rand())} {
   last_sky_offset_ = sky_offset_;
 }
@@ -20,9 +22,10 @@ SkyQuad::~SkyQuad() = default;
 
 bool SkyQuad::Create(bool without_nebula) {
   without_nebula_ = without_nebula;
+  if (!CreateShaders())
+    return false;
+
   scale_ = Engine::Get().GetScreenSize();
-  shader_ = Engine::Get().GetCustomShader(
-      without_nebula ? "sky_without_nebula" : "sky");
 
   color_animator_.Attach(this);
 
@@ -51,6 +54,10 @@ void SkyQuad::Draw(float frame_frac) {
   Engine::Get().GetQuad()->Draw();
 }
 
+void SkyQuad::ContextLost() {
+  CreateShaders();
+}
+
 void SkyQuad::SwitchColor(const Vector4f& color) {
   color_animator_.Pause(Animator::kBlending);
   color_animator_.SetTime(Animator::kBlending, 0);
@@ -59,6 +66,17 @@ void SkyQuad::SwitchColor(const Vector4f& color) {
   color_animator_.Play(Animator::kBlending, false);
 }
 
+bool SkyQuad::CreateShaders() {
+  Engine& engine = Engine::Get();
+
+  auto source = std::make_unique<ShaderSource>();
+  if (!source->Load(without_nebula_ ? "sky_without_nebula.glsl" : "sky.glsl"))
+    return false;
+  shader_->Create(std::move(source), engine.GetQuad()->vertex_description(),
+                  Engine::Get().GetQuad()->primitive(), false);
+  return true;
+}
+
 void SkyQuad::SetSpeed(float speed) {
   speed_ = speed;
 }

src/demo/sky_quad.h

@@ -36,6 +36,8 @@ class SkyQuad : public eng::Animatable {
   // Drawable interface.
   void Draw(float frame_frac) final;
 
+  void ContextLost();
+
   void SwitchColor(const base::Vector4f& color);
 
   void SetSpeed(float speed);
@@ -43,7 +45,7 @@ class SkyQuad : public eng::Animatable {
   const base::Vector4f& nebula_color() { return nebula_color_; }
 
  private:
-  eng::Shader* shader_;
+  std::unique_ptr<eng::Shader> shader_;
 
   base::Vector2f sky_offset_ = {0, 0};
   base::Vector2f last_sky_offset_ = {0, 0};
@@ -55,6 +57,8 @@ class SkyQuad : public eng::Animatable {
   float speed_ = 0;
 
   bool without_nebula_ = false;
+
+  bool CreateShaders();
 };
 
 #endif  // DEMO_SKY_QUAD_H

src/engine/animator.cc

@@ -126,10 +126,10 @@ void Animator::SetMovement(Vector2f direction,
     a.movement_last_pos = {0, 0};
 }
 
-void Animator::SetRotation(float target,
+void Animator::SetRotation(float trget,
                            float duration,
                            Interpolator interpolator) {
-  rotation_target_ = target;
+  rotation_target_ = trget;
   rotation_speed_ = 1.0f / duration;
   rotation_interpolator_ = std::move(interpolator);
 
@@ -153,7 +153,7 @@ void Animator::SetFrames(int count,
   frame_count_ = count;
   frame_speed_ = (float)frames_per_second / (float)count;
   for (auto& a : elements_)
-    a.frame_start = a.animatable->GetFrame();
+    a.frame_start_ = a.animatable->GetFrame();
   frame_interpolator_ = std::move(interpolator);
 }
 
@@ -180,43 +180,66 @@ void Animator::Update(float delta_time) {
     UpdateAnimTime(delta_time, kFrames, frame_speed_, frame_time_, frame_cb_);
   if (play_flags_ & kTimer)
     UpdateAnimTime(delta_time, kTimer, timer_speed_, timer_time_, timer_cb_);
+
+  did_evaluate_ = false;
 }
 
-void Animator::Evaluate(float frame_frac) {
-  if (play_flags_ & kMovement)
-    EvaluateAnimation<Vector2f, true>(
-        frame_frac, movement_speed_, movement_time_, movement_interpolator_,
-        movement_direction_, [](Element& a, Vector2f pos) {
-          a.animatable->Translate(pos - a.movement_last_pos);
-          a.movement_last_pos = pos;
-        });
+void Animator::Evaluate(float frame_frac_time) {
+  did_evaluate_ = true;
 
-  if (play_flags_ & kRotation)
-    EvaluateAnimation<float, true>(
-        frame_frac, rotation_speed_, rotation_time_, rotation_interpolator_,
-        rotation_target_, [](Element& a, float theta) {
-          a.animatable->Rotate(theta - a.rotation_last_theta);
-          a.rotation_last_theta = theta;
-        });
+  Vector2f pos = {0, 0};
+  if (play_flags_ & kMovement) {
+    float time = movement_time_ + movement_speed_ * frame_frac_time;
+    float interpolated_time =
+        movement_interpolator_ ? movement_interpolator_(time) : time;
+    pos = base::Lerp({0, 0}, movement_direction_, interpolated_time);
+  }
 
-  if (play_flags_ & kBlending)
-    EvaluateAnimation<float, false>(
-        frame_frac, blending_speed_, blending_time_, blending_interpolator_, {},
-        [&](Element& a, float interpolated_time) {
-          Vector4f blending =
-              base::Lerp(a.blending_start, blending_target_, interpolated_time);
-          a.animatable->SetColor(blending);
-        });
+  float theta = 0;
+  if (play_flags_ & kRotation) {
+    float time = rotation_time_ + rotation_speed_ * frame_frac_time;
+    float interpolated_time =
+        rotation_interpolator_ ? rotation_interpolator_(time) : time;
+    theta = base::Lerp(0.0f, rotation_target_, interpolated_time);
+  }
 
-  if (play_flags_ & kFrames)
-    EvaluateAnimation<float, false>(
-        frame_frac, frame_speed_, frame_time_, frame_interpolator_, {},
-        [&](Element& a, float interpolated_time) {
-          int target = a.frame_start + frame_count_;
-          int frame = base::Lerp(a.frame_start, target, interpolated_time);
-          if (frame < target)
-            a.animatable->SetFrame(frame);
-        });
+  float blending_itime = 0;
+  if (play_flags_ & kBlending) {
+    float time = blending_time_ + blending_speed_ * frame_frac_time;
+    blending_itime =
+        blending_interpolator_ ? blending_interpolator_(time) : time;
+  }
+
+  float frame_itime = 0;
+  if (play_flags_ & kFrames) {
+    float time = frame_time_ + frame_speed_ * frame_frac_time;
+    frame_itime = frame_interpolator_ ? frame_interpolator_(time) : time;
+  }
+
+  for (auto& a : elements_) {
+    if (play_flags_ & kMovement) {
+      a.animatable->Translate(pos - a.movement_last_pos);
+      a.movement_last_pos = pos;
+    }
+
+    if (play_flags_ & kRotation) {
+      a.animatable->Rotate(theta - a.rotation_last_theta);
+      a.rotation_last_theta = theta;
+    }
+
+    if (play_flags_ & kBlending) {
+      Vector4f blending =
+          base::Lerp(a.blending_start, blending_target_, blending_itime);
+      a.animatable->SetColor(blending);
+    }
+
+    if (play_flags_ & kFrames) {
+      int target = a.frame_start_ + frame_count_;
+      int frame = base::Lerp(a.frame_start_, target, frame_itime);
+      if (frame < target)
+        a.animatable->SetFrame(frame);
+    }
+  }
 }
 
 void Animator::UpdateAnimTime(float delta_time,
@@ -229,8 +252,8 @@ void Animator::UpdateAnimTime(float delta_time,
     if (loop_flags_ & anim) {
       anim_time = fmod(anim_time, 1.0f);
     } else {
-      anim_time = 1.0f;
-      Evaluate(0);
+      if (!did_evaluate_)
+        Evaluate(0);
       anim_time = 0;
       play_flags_ &= ~anim;
       if (cb) {
@@ -246,24 +269,4 @@ void Animator::UpdateAnimTime(float delta_time,
   }
 }
 
-template <typename T, bool relative>
-void Animator::EvaluateAnimation(float frame_frac,
-                                 float anim_speed,
-                                 float anim_time,
-                                 Interpolator& interpolator,
-                                 T target,
-                                 ResultSetter<T> set_result) {
-  float time = anim_time + anim_speed * frame_frac;
-  float interpolated_time = interpolator ? interpolator(time) : time;
-
-  if constexpr (relative) {
-    T result = base::Lerp(T{0}, target, interpolated_time);
-    for (auto& a : elements_)
-      set_result(a, result);
-  } else {
-    for (auto& a : elements_)
-      set_result(a, interpolated_time);
-  }
-}
-
 }  // namespace eng

src/engine/animator.h

@@ -40,7 +40,7 @@ class Animator {
   float GetTime(int animation);
   void SetTime(int animation, float time, bool force_update = false);
 
-  // Set callback to be called once animation ends.
+  // Set callback ro be called once animation ends.
   void SetEndCallback(int animation, base::Closure cb);
 
   // Distance is the magnitude of direction vector. Duration is in seconds.
@@ -69,7 +69,7 @@ class Animator {
   void SetVisible(bool visible);
 
   void Update(float delta_time);
-  void Evaluate(float frame_frac);
+  void Evaluate(float frame_frac_time);
 
   bool IsPlaying(int animation) const { return play_flags_ & animation; }
 
@@ -79,7 +79,7 @@ class Animator {
     base::Vector2f movement_last_pos = {0, 0};
     float rotation_last_theta = 0;
     base::Vector4f blending_start = {0, 0, 0, 0};
-    int frame_start = 0;
+    int frame_start_ = 0;
   };
 
   unsigned int play_flags_ = 0;
@@ -120,22 +120,13 @@ class Animator {
   base::Closure pending_cb_;
   Flags inside_cb_ = kNone;
 
+  bool did_evaluate_ = false;
+
   void UpdateAnimTime(float delta_time,
                       int anim,
                       float anim_speed,
                       float& anim_time,
                       base::Closure& cb);
-
-  template <typename T>
-  using ResultSetter = std::function<void(Element&, T)>;
-
-  template <typename T, bool relative>
-  void EvaluateAnimation(float frame_frac,
-                         float anim_speed,
-                         float anim_time,
-                         Interpolator& interpolator,
-                         T target,
-                         ResultSetter<T> set_result);
 };
 
 }  // namespace eng

src/engine/audio/audio.h

@@ -0,0 +1,20 @@
+#ifndef ENGINE_AUDIO_AUDIO_H
+#define ENGINE_AUDIO_AUDIO_H
+
+#if defined(__ANDROID__)
+#include "engine/audio/audio_oboe.h"
+#elif defined(__linux__)
+#include "engine/audio/audio_alsa.h"
+#endif
+
+namespace eng {
+
+#if defined(__ANDROID__)
+using Audio = AudioOboe;
+#elif defined(__linux__)
+using Audio = AudioAlsa;
+#endif
+
+}  // namespace eng
+
+#endif  // ENGINE_AUDIO_AUDIO_H

src/engine/audio/audio_alsa.cc

@@ -1,26 +1,20 @@
-#include "engine/audio/audio_driver_alsa.h"
+#include "engine/audio/audio_alsa.h"
 
 #include <memory>
 
 #include <alsa/asoundlib.h>
 
 #include "base/log.h"
-#include "engine/audio/audio_driver_delegate.h"
 
 using namespace base;
 
 namespace eng {
 
-AudioDriverAlsa::AudioDriverAlsa() = default;
+AudioAlsa::AudioAlsa() = default;
 
-AudioDriverAlsa::~AudioDriverAlsa() = default;
+AudioAlsa::~AudioAlsa() = default;
 
-void AudioDriverAlsa::SetDelegate(AudioDriverDelegate* delegate) {
-  delegate_ = delegate;
-  Resume();
-}
-
-bool AudioDriverAlsa::Initialize() {
+bool AudioAlsa::Initialize() {
   LOG << "Initializing audio system.";
 
   int err;
@@ -142,43 +136,51 @@ bool AudioDriverAlsa::Initialize() {
   return false;
 }
 
-void AudioDriverAlsa::Shutdown() {
+void AudioAlsa::Shutdown() {
   LOG << "Shutting down audio system.";
+
   TerminateAudioThread();
   snd_pcm_drop(device_);
   snd_pcm_close(device_);
 }
 
-void AudioDriverAlsa::Suspend() {
+void AudioAlsa::Suspend() {
+  DCHECK(!terminate_audio_thread_.load(std::memory_order_relaxed));
+
   suspend_audio_thread_.store(true, std::memory_order_relaxed);
 }
 
-void AudioDriverAlsa::Resume() {
+void AudioAlsa::Resume() {
+  DCHECK(!terminate_audio_thread_.load(std::memory_order_relaxed));
+
   suspend_audio_thread_.store(false, std::memory_order_relaxed);
 }
 
-int AudioDriverAlsa::GetHardwareSampleRate() {
+int AudioAlsa::GetHardwareSampleRate() {
   return sample_rate_;
 }
 
-void AudioDriverAlsa::StartAudioThread() {
+void AudioAlsa::StartAudioThread() {
   LOG << "Starting audio thread.";
-  terminate_audio_thread_.store(false, std::memory_order_relaxed);
-  suspend_audio_thread_.store(true, std::memory_order_relaxed);
-  audio_thread_ = std::thread(&AudioDriverAlsa::AudioThreadMain, this);
+
+  DCHECK(!terminate_audio_thread_.load(std::memory_order_relaxed));
+
+  audio_thread_ = std::thread(&AudioAlsa::AudioThreadMain, this);
 }
 
-void AudioDriverAlsa::TerminateAudioThread() {
+void AudioAlsa::TerminateAudioThread() {
   if (terminate_audio_thread_.load(std::memory_order_relaxed))
     return;
 
   LOG << "Terminating audio thread";
+
+  // Notify worker thread and wait for it to terminate.
   terminate_audio_thread_.store(true, std::memory_order_relaxed);
   suspend_audio_thread_.store(true, std::memory_order_relaxed);
   audio_thread_.join();
 }
 
-void AudioDriverAlsa::AudioThreadMain() {
+void AudioAlsa::AudioThreadMain() {
   size_t num_frames = period_size_ / (num_channels_ * sizeof(float));
   auto buffer = std::make_unique<float[]>(num_frames * 2);
 
@@ -190,11 +192,11 @@ void AudioDriverAlsa::AudioThreadMain() {
       std::this_thread::sleep_for(std::chrono::milliseconds(1));
     }
 
-    delegate_->RenderAudio(buffer.get(), num_frames);
+    RenderAudio(buffer.get(), num_frames);
 
     while (snd_pcm_writei(device_, buffer.get(), num_frames) < 0) {
       snd_pcm_prepare(device_);
-      DLOG << "Alsa buffer underrun!";
+      DLOG << "Audio buffer underrun!";
     }
   }
 }

src/engine/audio/audio_alsa.h

@@ -0,0 +1,47 @@
+#ifndef ENGINE_AUDIO_AUDIO_ALSA_H
+#define ENGINE_AUDIO_AUDIO_ALSA_H
+
+#include <atomic>
+#include <thread>
+
+#include "engine/audio/audio_base.h"
+
+typedef struct _snd_pcm snd_pcm_t;
+
+namespace eng {
+
+class AudioAlsa : public AudioBase {
+ public:
+  AudioAlsa();
+  ~AudioAlsa();
+
+  bool Initialize();
+
+  void Shutdown();
+
+  void Suspend();
+  void Resume();
+
+  int GetHardwareSampleRate();
+
+ private:
+  // Handle for the PCM device.
+  snd_pcm_t* device_;
+
+  std::thread audio_thread_;
+  std::atomic<bool> terminate_audio_thread_{false};
+  std::atomic<bool> suspend_audio_thread_{false};
+
+  size_t num_channels_ = 0;
+  int sample_rate_ = 0;
+  size_t period_size_ = 0;
+
+  void StartAudioThread();
+  void TerminateAudioThread();
+
+  void AudioThreadMain();
+};
+
+}  // namespace eng
+
+#endif  // ENGINE_AUDIO_AUDIO_ALSA_H

src/engine/audio/audio_base.cc

@@ -1,4 +1,4 @@
-#include "engine/audio/audio_mixer.h"
+#include "engine/audio/audio.h"
 
 #include <cstring>
 
@@ -11,33 +11,30 @@ using namespace base;
 
 namespace eng {
 
-AudioMixer::AudioMixer()
+AudioBase::AudioBase()
     : main_thread_task_runner_(TaskRunner::GetThreadLocalTaskRunner()) {}
 
-AudioMixer::~AudioMixer() = default;
+AudioBase::~AudioBase() = default;
 
-uint64_t AudioMixer::CreateResource() {
+uint64_t AudioBase::CreateResource() {
   uint64_t resource_id = ++last_resource_id_;
   resources_[resource_id] = std::make_shared<Resource>();
   return resource_id;
 }
 
-void AudioMixer::DestroyResource(uint64_t resource_id) {
+void AudioBase::DestroyResource(uint64_t resource_id) {
   auto it = resources_.find(resource_id);
   if (it == resources_.end())
     return;
 
-  if (it->second->active) {
-    it->second->restart_cb = nullptr;
-    it->second->flags.fetch_or(kStopped, std::memory_order_relaxed);
-  }
+  it->second->flags.fetch_or(kStopped, std::memory_order_relaxed);
   resources_.erase(it);
 }
 
-void AudioMixer::Play(uint64_t resource_id,
-                      std::shared_ptr<Sound> sound,
-                      float amplitude,
-                      bool reset_pos) {
+void AudioBase::Play(uint64_t resource_id,
+                     std::shared_ptr<Sound> sound,
+                     float amplitude,
+                     bool reset_pos) {
   if (!audio_enabled_)
     return;
 
@@ -49,11 +46,15 @@ void AudioMixer::Play(uint64_t resource_id,
     if (reset_pos)
       it->second->flags.fetch_or(kStopped, std::memory_order_relaxed);
 
-    if (it->second->flags.load(std::memory_order_relaxed) & kStopped)
-      it->second->restart_cb = [&, resource_id, sound, amplitude,
-                                reset_pos]() -> void {
-        Play(resource_id, sound, amplitude, reset_pos);
-      };
+    if (it->second->flags.load(std::memory_order_relaxed) & kStopped) {
+      Closure ocb = std::move(it->second->end_cb);
+      SetEndCallback(
+          resource_id,
+          [&, resource_id, sound, amplitude, reset_pos, ocb]() -> void {
+            Play(resource_id, sound, amplitude, reset_pos);
+            SetEndCallback(resource_id, std::move(ocb));
+          });
+    }
 
     return;
   }
@@ -74,18 +75,16 @@ void AudioMixer::Play(uint64_t resource_id,
   play_list_[0].push_back(it->second);
 }
 
-void AudioMixer::Stop(uint64_t resource_id) {
+void AudioBase::Stop(uint64_t resource_id) {
   auto it = resources_.find(resource_id);
   if (it == resources_.end())
     return;
 
-  if (it->second->active) {
-    it->second->restart_cb = nullptr;
+  if (it->second->active)
     it->second->flags.fetch_or(kStopped, std::memory_order_relaxed);
-  }
 }
 
-void AudioMixer::SetLoop(uint64_t resource_id, bool loop) {
+void AudioBase::SetLoop(uint64_t resource_id, bool loop) {
   auto it = resources_.find(resource_id);
   if (it == resources_.end())
     return;
@@ -96,7 +95,7 @@ void AudioMixer::SetLoop(uint64_t resource_id, bool loop) {
     it->second->flags.fetch_and(~kLoop, std::memory_order_relaxed);
 }
 
-void AudioMixer::SetSimulateStereo(uint64_t resource_id, bool simulate) {
+void AudioBase::SetSimulateStereo(uint64_t resource_id, bool simulate) {
   auto it = resources_.find(resource_id);
   if (it == resources_.end())
     return;
@@ -107,7 +106,7 @@ void AudioMixer::SetSimulateStereo(uint64_t resource_id, bool simulate) {
     it->second->flags.fetch_and(~kSimulateStereo, std::memory_order_relaxed);
 }
 
-void AudioMixer::SetResampleStep(uint64_t resource_id, size_t step) {
+void AudioBase::SetResampleStep(uint64_t resource_id, size_t step) {
   auto it = resources_.find(resource_id);
   if (it == resources_.end())
     return;
@@ -115,7 +114,7 @@ void AudioMixer::SetResampleStep(uint64_t resource_id, size_t step) {
   it->second->step.store(step + 100, std::memory_order_relaxed);
 }
 
-void AudioMixer::SetMaxAmplitude(uint64_t resource_id, float max_amplitude) {
+void AudioBase::SetMaxAmplitude(uint64_t resource_id, float max_amplitude) {
   auto it = resources_.find(resource_id);
   if (it == resources_.end())
     return;
@@ -123,7 +122,7 @@ void AudioMixer::SetMaxAmplitude(uint64_t resource_id, float max_amplitude) {
   it->second->max_amplitude.store(max_amplitude, std::memory_order_relaxed);
 }
 
-void AudioMixer::SetAmplitudeInc(uint64_t resource_id, float amplitude_inc) {
+void AudioBase::SetAmplitudeInc(uint64_t resource_id, float amplitude_inc) {
   auto it = resources_.find(resource_id);
   if (it == resources_.end())
     return;
@@ -131,7 +130,7 @@ void AudioMixer::SetAmplitudeInc(uint64_t resource_id, float amplitude_inc) {
   it->second->amplitude_inc.store(amplitude_inc, std::memory_order_relaxed);
 }
 
-void AudioMixer::SetEndCallback(uint64_t resource_id, base::Closure cb) {
+void AudioBase::SetEndCallback(uint64_t resource_id, base::Closure cb) {
   auto it = resources_.find(resource_id);
   if (it == resources_.end())
     return;
@@ -139,7 +138,7 @@ void AudioMixer::SetEndCallback(uint64_t resource_id, base::Closure cb) {
   it->second->end_cb = std::move(cb);
 }
 
-void AudioMixer::RenderAudio(float* output_buffer, size_t num_frames) {
+void AudioBase::RenderAudio(float* output_buffer, size_t num_frames) {
   {
     std::unique_lock<std::mutex> scoped_lock(lock_, std::try_to_lock);
     if (scoped_lock)
@@ -208,18 +207,20 @@ void AudioMixer::RenderAudio(float* output_buffer, size_t num_frames) {
 
         // Remove, loop or stream if the source data is consumed
         if (src_index >= num_samples) {
-          if (num_samples)
+          if (!sound->is_streaming_sound()) {
             src_index %= num_samples;
 
-          if (!sound->is_streaming_sound()) {
             if (!(flags & kLoop)) {
               marked_for_removal = true;
               break;
             }
           } else if (!it->get()->streaming_in_progress.load(
                          std::memory_order_acquire)) {
+            if (num_samples)
+              src_index %= num_samples;
+
+            // Looping streaming sounds never return eof.
             if (sound->eof()) {
-              DCHECK((flags & kLoop) == 0);
               marked_for_removal = true;
               break;
             }
@@ -237,9 +238,10 @@ void AudioMixer::RenderAudio(float* output_buffer, size_t num_frames) {
 
             ThreadPool::Get().PostTask(
                 HERE,
-                std::bind(&AudioMixer::DoStream, this, *it, flags & kLoop));
+                std::bind(&AudioBase::DoStream, this, *it, flags & kLoop));
           } else if (num_samples) {
-            DLOG << "Mixer buffer underrun!";
+            DLOG << "Buffer underrun!";
+            src_index %= num_samples;
           }
         }
       }
@@ -261,7 +263,7 @@ void AudioMixer::RenderAudio(float* output_buffer, size_t num_frames) {
     if ((!it->get()->sound->is_streaming_sound() ||
          !it->get()->streaming_in_progress.load(std::memory_order_relaxed))) {
       main_thread_task_runner_->PostTask(
-          HERE, std::bind(&AudioMixer::EndCallback, this, *it));
+          HERE, std::bind(&AudioBase::EndCallback, this, *it));
       it = end_list_.erase(it);
     } else {
       ++it;
@@ -269,20 +271,19 @@ void AudioMixer::RenderAudio(float* output_buffer, size_t num_frames) {
   }
 }
 
-void AudioMixer::DoStream(std::shared_ptr<Resource> resource, bool loop) {
+void AudioBase::DoStream(std::shared_ptr<Resource> resource, bool loop) {
   resource->sound->Stream(loop);
+
+  // Memory barrier to ensure all memory writes become visible to the audio
+  // thread.
   resource->streaming_in_progress.store(false, std::memory_order_release);
 }
 
-void AudioMixer::EndCallback(std::shared_ptr<Resource> resource) {
+void AudioBase::EndCallback(std::shared_ptr<Resource> resource) {
   resource->active = false;
 
   if (resource->end_cb)
     resource->end_cb();
-  if (resource->restart_cb) {
-    resource->restart_cb();
-    resource->restart_cb = nullptr;
-  }
 }
 
 }  // namespace eng

src/engine/audio/audio_base.h

@@ -1,14 +1,12 @@
-#ifndef ENGINE_AUDIO_AUDIO_MIXER_H
-#define ENGINE_AUDIO_AUDIO_MIXER_H
+#ifndef ENGINE_AUDIO_AUDIO_BASE_H
+#define ENGINE_AUDIO_AUDIO_BASE_H
 
-#include <atomic>
 #include <list>
 #include <memory>
 #include <mutex>
 #include <unordered_map>
 
 #include "base/closure.h"
-#include "engine/audio/audio_driver_delegate.h"
 
 namespace base {
 class TaskRunner;
@@ -18,14 +16,11 @@ namespace eng {
 
 class Sound;
 
-// Mix and render audio with low overhead. A platform specific AudioDriver
-// implementation is expected to periodically call Render() in a background
+// Class representing the end-point for rendered audio. A platform specific
+// implementation is expected to periodically call RenderAudio() in a background
 // thread.
-class AudioMixer : public AudioDriverDelegate {
+class AudioBase {
  public:
-  AudioMixer();
-  ~AudioMixer();
-
   uint64_t CreateResource();
   void DestroyResource(uint64_t resource_id);
 
@@ -44,15 +39,21 @@ class AudioMixer : public AudioDriverDelegate {
 
   void SetEnableAudio(bool enable) { audio_enabled_ = enable; }
 
+ protected:
+  static constexpr int kChannelCount = 2;
+
+  AudioBase();
+  ~AudioBase();
+
+  void RenderAudio(float* output_buffer, size_t num_frames);
+
  private:
   enum SampleFlags { kLoop = 1, kStopped = 2, kSimulateStereo = 4 };
-  static constexpr int kChannelCount = 2;
 
   struct Resource {
     // Accessed by main thread only.
     bool active = false;
     base::Closure end_cb;
-    base::Closure restart_cb;
 
     // Initialized by main thread, used by audio thread.
     std::shared_ptr<Sound> sound;
@@ -82,17 +83,14 @@ class AudioMixer : public AudioDriverDelegate {
 
   bool audio_enabled_ = true;
 
-  // AudioDriverDelegate implementation
-  void RenderAudio(float* output_buffer, size_t num_frames) final;
-
   void DoStream(std::shared_ptr<Resource> sample, bool loop);
 
   void EndCallback(std::shared_ptr<Resource> sample);
 
-  AudioMixer(const AudioMixer&) = delete;
-  AudioMixer& operator=(const AudioMixer&) = delete;
+  AudioBase(const AudioBase&) = delete;
+  AudioBase& operator=(const AudioBase&) = delete;
 };
 
 }  // namespace eng
 
-#endif  // ENGINE_AUDIO_AUDIO_MIXER_H
+#endif  // ENGINE_AUDIO_AUDIO_BASE_H

src/engine/audio/audio_driver.h

@@ -1,35 +0,0 @@
-#ifndef ENGINE_AUDIO_AUDIO_DRIVER_H
-#define ENGINE_AUDIO_AUDIO_DRIVER_H
-
-#include "engine/audio/audio_driver.h"
-
-namespace eng {
-
-class AudioDriverDelegate;
-
-// Models an audio sink sending mixed audio to the audio driver. Audio data from
-// the mixer source is delivered on a pull model using AudioDriverDelegate.
-class AudioDriver {
- public:
-  AudioDriver() = default;
-  virtual ~AudioDriver() = default;
-
-  virtual void SetDelegate(AudioDriverDelegate* delegate) = 0;
-
-  virtual bool Initialize() = 0;
-
-  virtual void Shutdown() = 0;
-
-  virtual void Suspend() = 0;
-  virtual void Resume() = 0;
-
-  virtual int GetHardwareSampleRate() = 0;
-
- private:
-  AudioDriver(const AudioDriver&) = delete;
-  AudioDriver& operator=(const AudioDriver&) = delete;
-};
-
-}  // namespace eng
-
-#endif  // ENGINE_AUDIO_AUDIO_DRIVER_H

src/engine/audio/audio_driver_alsa.h

@@ -1,51 +0,0 @@
-#ifndef ENGINE_AUDIO_AUDIO_DRIVER_ALSA_H
-#define ENGINE_AUDIO_AUDIO_DRIVER_ALSA_H
-
-#include <atomic>
-#include <thread>
-
-#include "engine/audio/audio_driver.h"
-
-typedef struct _snd_pcm snd_pcm_t;
-
-namespace eng {
-
-class AudioDriverAlsa final : public AudioDriver {
- public:
-  AudioDriverAlsa();
-  ~AudioDriverAlsa() final;
-
-  void SetDelegate(AudioDriverDelegate* delegate) final;
-
-  bool Initialize() final;
-
-  void Shutdown() final;
-
-  void Suspend() final;
-  void Resume() final;
-
-  int GetHardwareSampleRate() final;
-
- private:
-  // Handle for the PCM device.
-  snd_pcm_t* device_;
-
-  std::thread audio_thread_;
-  std::atomic<bool> terminate_audio_thread_{false};
-  std::atomic<bool> suspend_audio_thread_{false};
-
-  size_t num_channels_ = 0;
-  int sample_rate_ = 0;
-  size_t period_size_ = 0;
-
-  AudioDriverDelegate* delegate_ = nullptr;
-
-  void StartAudioThread();
-  void TerminateAudioThread();
-
-  void AudioThreadMain();
-};
-
-}  // namespace eng
-
-#endif  // ENGINE_AUDIO_AUDIO_DRIVER_ALSA_H

src/engine/audio/audio_driver_delegate.h

@@ -1,18 +0,0 @@
-#ifndef ENGINE_AUDIO_AUDIO_DRIVER_DELEGATE_H
-#define ENGINE_AUDIO_AUDIO_DRIVER_DELEGATE_H
-
-#include <stddef.h>
-
-namespace eng {
-
-class AudioDriverDelegate {
- public:
-  AudioDriverDelegate() = default;
-  virtual ~AudioDriverDelegate() = default;
-
-  virtual void RenderAudio(float* output_buffer, size_t num_frames) = 0;
-};
-
-}  // namespace eng
-
-#endif  // ENGINE_AUDIO_AUDIO_DRIVER_DELEGATE_H

src/engine/audio/audio_forward.h

@@ -0,0 +1,16 @@
+#ifndef ENGINE_AUDIO_AUDIO_FORWARD_H
+#define ENGINE_AUDIO_AUDIO_FORWARD_H
+
+namespace eng {
+
+#if defined(__ANDROID__)
+class AudioOboe;
+using Audio = AudioOboe;
+#elif defined(__linux__)
+class AudioAlsa;
+using Audio = AudioAlsa;
+#endif
+
+}  // namespace eng
+
+#endif  // ENGINE_AUDIO_AUDIO_FORWARD_H

src/engine/audio/audio_oboe.cc

@@ -1,70 +1,62 @@
-#include "engine/audio/audio_driver_oboe.h"
+#include "engine/audio/audio_oboe.h"
 
 #include "base/log.h"
-#include "engine/audio/audio_driver_delegate.h"
 #include "third_party/oboe/include/oboe/Oboe.h"
 
 using namespace base;
 
 namespace eng {
 
-AudioDriverOboe::AudioDriverOboe()
-    : callback_(std::make_unique<StreamCallback>(this)) {}
+AudioOboe::AudioOboe() : callback_(std::make_unique<StreamCallback>(this)) {}
 
-AudioDriverOboe::~AudioDriverOboe() = default;
+AudioOboe::~AudioOboe() = default;
 
-void AudioDriverOboe::SetDelegate(AudioDriverDelegate* delegate) {
-  delegate_ = delegate;
-  Resume();
-}
-
-bool AudioDriverOboe::Initialize() {
+bool AudioOboe::Initialize() {
   LOG << "Initializing audio system.";
 
-  return RestartStream(true);
+  return RestartStream();
 }
 
-void AudioDriverOboe::Shutdown() {
+void AudioOboe::Shutdown() {
   LOG << "Shutting down audio system.";
 
   stream_->stop();
 }
 
-void AudioDriverOboe::Suspend() {
+void AudioOboe::Suspend() {
   stream_->stop();
 }
 
-void AudioDriverOboe::Resume() {
+void AudioOboe::Resume() {
   RestartStream();
 }
 
-int AudioDriverOboe::GetHardwareSampleRate() {
+int AudioOboe::GetHardwareSampleRate() {
   return stream_->getSampleRate();
 }
 
-AudioDriverOboe::StreamCallback::StreamCallback(AudioDriverOboe* driver)
-    : driver_(driver) {}
+AudioOboe::StreamCallback::StreamCallback(AudioOboe* audio) : audio_(audio) {}
 
-AudioDriverOboe::StreamCallback::~StreamCallback() = default;
+AudioOboe::StreamCallback::~StreamCallback() = default;
 
-oboe::DataCallbackResult AudioDriverOboe::StreamCallback::onAudioReady(
+oboe::DataCallbackResult AudioOboe::StreamCallback::onAudioReady(
     oboe::AudioStream* oboe_stream,
     void* audio_data,
     int32_t num_frames) {
   float* output_buffer = static_cast<float*>(audio_data);
-  driver_->delegate_->RenderAudio(output_buffer, num_frames);
+  audio_->RenderAudio(output_buffer, num_frames);
   return oboe::DataCallbackResult::Continue;
 }
 
-void AudioDriverOboe::StreamCallback::onErrorAfterClose(
+void AudioOboe::StreamCallback::onErrorAfterClose(
     oboe::AudioStream* oboe_stream,
     oboe::Result error) {
   LOG << "Error after close. Error: " << oboe::convertToText(error);
 
-  driver_->RestartStream();
+  audio_->RestartStream();
 }
 
-bool AudioDriverOboe::RestartStream(bool suspended) {
+bool AudioOboe::RestartStream() {
   oboe::AudioStreamBuilder builder;
   oboe::Result result =
       builder.setSharingMode(oboe::SharingMode::Exclusive)
@@ -88,8 +80,7 @@ bool AudioDriverOboe::RestartStream(bool suspended) {
     return false;
   }
 
-  if (!suspended)
-    stream_->start();
+  stream_->start();
   return true;
 }
 

src/engine/audio/audio_oboe.h

@@ -1,37 +1,33 @@
-#ifndef ENGINE_AUDIO_AUDIO_DRIVER_OBOE_H
-#define ENGINE_AUDIO_AUDIO_DRIVER_OBOE_H
+#ifndef ENGINE_AUDIO_AUDIO_OBOE_H
+#define ENGINE_AUDIO_AUDIO_OBOE_H
 
 #include <memory>
 
 #include "third_party/oboe/include/oboe/AudioStream.h"
 #include "third_party/oboe/include/oboe/AudioStreamCallback.h"
 
-#include "engine/audio/audio_driver.h"
+#include "engine/audio/audio_base.h"
 
 namespace eng {
 
-class AudioDriverOboe final : public AudioDriver {
+class AudioOboe : public AudioBase {
  public:
-  AudioDriverOboe();
-  ~AudioDriverOboe() final;
+  AudioOboe();
+  ~AudioOboe();
 
-  void SetDelegate(AudioDriverDelegate* delegate) final;
+  bool Initialize();
 
-  bool Initialize() final;
+  void Shutdown();
 
-  void Shutdown() final;
+  void Suspend();
+  void Resume();
 
-  void Suspend() final;
-  void Resume() final;
-
-  int GetHardwareSampleRate() final;
+  int GetHardwareSampleRate();
 
  private:
-  static constexpr int kChannelCount = 2;
-
   class StreamCallback final : public oboe::AudioStreamCallback {
    public:
-    StreamCallback(AudioDriverOboe* audio);
+    StreamCallback(AudioOboe* audio);
     ~StreamCallback() final;
 
     oboe::DataCallbackResult onAudioReady(oboe::AudioStream* oboe_stream,
@@ -42,17 +38,15 @@ class AudioDriverOboe final : public AudioDriver {
                            oboe::Result error) final;
 
    private:
-    AudioDriverOboe* driver_;
+    AudioOboe* audio_;
   };
 
   oboe::ManagedStream stream_;
   std::unique_ptr<StreamCallback> callback_;
 
-  AudioDriverDelegate* delegate_ = nullptr;
-
-  bool RestartStream(bool suspended = false);
+  bool RestartStream();
 };
 
 }  // namespace eng
 
-#endif  // ENGINE_AUDIO_AUDIO_DRIVER_OBOE_H
+#endif  // ENGINE_AUDIO_AUDIO_OBOE_H

src/engine/engine.cc

@@ -2,8 +2,7 @@
 
 #include "base/log.h"
 #include "engine/animator.h"
-#include "engine/audio/audio_driver.h"
-#include "engine/audio/audio_mixer.h"
+#include "engine/audio/audio.h"
 #include "engine/drawable.h"
 #include "engine/font.h"
 #include "engine/game.h"
@@ -26,17 +25,11 @@ namespace eng {
 
 Engine* Engine::singleton = nullptr;
 
-Engine::Engine(Platform* platform,
-               Renderer* renderer,
-               AudioDriver* audio_driver)
-    : platform_(platform),
-      renderer_(renderer),
-      audio_driver_(audio_driver),
-      audio_mixer_{std::make_unique<AudioMixer>()} {
+Engine::Engine(Platform* platform, Renderer* renderer, Audio* audio)
+    : platform_(platform), renderer_(renderer), audio_(audio) {
   DCHECK(!singleton);
   singleton = this;
 
-  audio_driver_->SetDelegate(audio_mixer_.get());
   renderer_->SetContextLostCB(std::bind(&Engine::ContextLost, this));
 
   quad_ = CreateRenderResource<Geometry>();
@@ -116,7 +109,6 @@ void Engine::Shutdown() {
   game_.reset();
   stats_->Destory();
   textures_.clear();
-  shaders_.clear();
 }
 
 void Engine::Update(float delta_time) {
@@ -158,14 +150,14 @@ void Engine::Draw(float frame_frac) {
 }
 
 void Engine::LostFocus() {
-  audio_driver_->Suspend();
+  audio_->Suspend();
 
   if (game_)
     game_->LostFocus();
 }
 
 void Engine::GainedFocus(bool from_interstitial_ad) {
-  audio_driver_->Resume();
+  audio_->Resume();
 
   if (game_)
     game_->GainedFocus(from_interstitial_ad);
@@ -285,42 +277,6 @@ void Engine::ReleaseTexture(const std::string& asset_name) {
     it->second.texture->Destroy();
 }
 
-void Engine::LoadCustomShader(const std::string& asset_name,
-                              const std::string& file_name) {
-  if (shaders_.contains(asset_name)) {
-    DLOG << "Shader already exists: " << asset_name;
-    return;
-  }
-
-  auto& s = shaders_[asset_name] = {CreateRenderResource<Shader>(), file_name};
-
-  auto source = std::make_unique<ShaderSource>();
-  if (!source->Load(file_name))
-    return;
-  s.shader->Create(std::move(source), quad_->vertex_description(),
-                   quad_->primitive(), false);
-}
-
-Shader* Engine::GetCustomShader(const std::string& asset_name) {
-  auto it = shaders_.find(asset_name);
-  if (it == shaders_.end()) {
-    DLOG << "Shader not found: " << asset_name;
-    return nullptr;
-  }
-
-  return it->second.shader.get();
-}
-
-void Engine::RemoveCustomShader(const std::string& asset_name) {
-  auto it = shaders_.find(asset_name);
-  if (it == shaders_.end()) {
-    DLOG << "Shader not found: " << asset_name;
-    return;
-  }
-
-  shaders_.erase(it);
-}
-
 void Engine::AddInputEvent(std::unique_ptr<InputEvent> event) {
   if (replaying_)
     return;
@@ -443,7 +399,7 @@ void Engine::SetKeepScreenOn(bool keep_screen_on) {
 }
 
 void Engine::SetEnableAudio(bool enable) {
-  audio_mixer_->SetEnableAudio(enable);
+  audio_->SetEnableAudio(enable);
 }
 
 TextureCompressor* Engine::GetTextureCompressor(bool opacity) {
@@ -481,7 +437,7 @@ const std::string& Engine::GetSharedDataPath() const {
 }
 
 int Engine::GetAudioHardwareSampleRate() {
-  return audio_driver_->GetHardwareSampleRate();
+  return audio_->GetHardwareSampleRate();
 }
 
 bool Engine::IsMobile() const {
@@ -496,13 +452,6 @@ void Engine::ContextLost() {
     RefreshImage(t.first);
   }
 
-  for (auto& s : shaders_) {
-    auto source = std::make_unique<ShaderSource>();
-    if (source->Load(s.second.file_name))
-      s.second.shader->Create(std::move(source), quad_->vertex_description(),
-                              quad_->primitive(), false);
-  }
-
   game_->ContextLost();
 }
 

src/engine/engine.h

@@ -9,6 +9,7 @@
 
 #include "base/random.h"
 #include "base/vecmath.h"
+#include "engine/audio/audio_forward.h"
 #include "engine/persistent_data.h"
 
 class TextureCompressor;
@@ -16,8 +17,6 @@ class TextureCompressor;
 namespace eng {
 
 class Animator;
-class AudioDriver;
-class AudioMixer;
 class Font;
 class Game;
 class Drawable;
@@ -34,7 +33,7 @@ class Engine {
  public:
   using CreateImageCB = std::function<std::unique_ptr<Image>()>;
 
-  Engine(Platform* platform, Renderer* renderer, AudioDriver* audio_driver);
+  Engine(Platform* platform, Renderer* renderer, Audio* audio);
   ~Engine();
 
   static Engine& Get();
@@ -80,11 +79,6 @@ class Engine {
   Texture* AcquireTexture(const std::string& asset_name);
   void ReleaseTexture(const std::string& asset_name);
 
-  void LoadCustomShader(const std::string& asset_name,
-                        const std::string& file_name);
-  Shader* GetCustomShader(const std::string& asset_name);
-  void RemoveCustomShader(const std::string& asset_name);
-
   void AddInputEvent(std::unique_ptr<InputEvent> event);
   std::unique_ptr<InputEvent> GetNextInputEvent();
 
@@ -108,7 +102,7 @@ class Engine {
 
   void SetEnableVibration(bool enable) { vibration_enabled_ = enable; }
 
-  AudioMixer* GetAudioMixer() { return audio_mixer_.get(); }
+  Audio* GetAudio() { return audio_; }
 
   // Access to the render resources.
   Geometry* GetQuad() { return quad_.get(); }
@@ -164,19 +158,14 @@ class Engine {
     size_t use_count = 0;
   };
 
-  // Class holding information about shader resources managed by engine.
-  struct ShaderResource {
-    std::unique_ptr<Shader> shader;
-    std::string file_name;
-  };
-
   static Engine* singleton;
 
   Platform* platform_ = nullptr;
-  Renderer* renderer_ = nullptr;
-  AudioDriver* audio_driver_ = nullptr;
 
-  std::unique_ptr<AudioMixer> audio_mixer_;
+  Renderer* renderer_ = nullptr;
+
+  Audio* audio_ = nullptr;
+
   std::unique_ptr<Game> game_;
 
   std::unique_ptr<Geometry> quad_;
@@ -195,9 +184,8 @@ class Engine {
 
   std::list<Animator*> animators_;
 
-  // Managed render resources mapped by asset name.
+  // Textures mapped by asset name.
   std::unordered_map<std::string, TextureResource> textures_;
-  std::unordered_map<std::string, ShaderResource> shaders_;
 
   std::unique_ptr<ImageQuad> stats_;
 

src/engine/image_quad.cc

@@ -49,8 +49,8 @@ void ImageQuad::AutoScale() {
   SetSize(size);
 }
 
-void ImageQuad::SetCustomShader(const std::string& asset_name) {
-  custom_shader_ = Engine::Get().GetCustomShader(asset_name);
+void ImageQuad::SetCustomShader(Shader* shader) {
+  custom_shader_ = shader;
   custom_uniforms_.clear();
 }
 

src/engine/image_quad.h

@@ -28,7 +28,7 @@ class ImageQuad final : public Animatable {
 
   void AutoScale();
 
-  void SetCustomShader(const std::string& asset_name);
+  void SetCustomShader(Shader* shader);
 
   template <typename T>
   void SetCustomUniform(const std::string& name, T value) {

src/engine/platform/platform.cc

@@ -2,16 +2,11 @@
 
 #include "base/log.h"
 #include "base/task_runner.h"
+#include "engine/audio/audio.h"
 #include "engine/engine.h"
 #include "engine/renderer/opengl/renderer_opengl.h"
 #include "engine/renderer/vulkan/renderer_vulkan.h"
 
-#if defined(__ANDROID__)
-#include "engine/audio/audio_driver_oboe.h"
-#elif defined(__linux__)
-#include "engine/audio/audio_driver_alsa.h"
-#endif
-
 using namespace base;
 
 namespace eng {
@@ -28,13 +23,9 @@ void Platform::InitializeCommon() {
   thread_pool_.Initialize();
   TaskRunner::CreateThreadLocalTaskRunner();
 
-#if defined(__ANDROID__)
-  audio_driver_ = std::make_unique<AudioDriverOboe>();
-#elif defined(__linux__)
-  audio_driver_ = std::make_unique<AudioDriverAlsa>();
-#endif
-  if (!audio_driver_->Initialize()) {
-    LOG << "Failed to initialize audio driver.";
+  audio_ = std::make_unique<Audio>();
+  if (!audio_->Initialize()) {
+    LOG << "Failed to initialize audio system.";
     throw internal_error;
   }
 
@@ -50,13 +41,12 @@ void Platform::InitializeCommon() {
 void Platform::ShutdownCommon() {
   LOG << "Shutting down platform.";
 
-  audio_driver_->Shutdown();
+  audio_->Shutdown();
   renderer_->Shutdown();
 }
 
 void Platform::RunMainLoop() {
-  engine_ =
-      std::make_unique<Engine>(this, renderer_.get(), audio_driver_.get());
+  engine_ = std::make_unique<Engine>(this, renderer_.get(), audio_.get());
   if (!engine_->Initialize()) {
     LOG << "Failed to initialize the engine.";
     throw internal_error;

src/engine/platform/platform.h

@@ -7,6 +7,7 @@
 
 #include "base/thread_pool.h"
 #include "base/timer.h"
+#include "engine/audio/audio_forward.h"
 
 #if defined(__ANDROID__)
 
@@ -24,7 +25,6 @@ struct AInputEvent;
 
 namespace eng {
 
-class AudioDriver;
 class Renderer;
 class Engine;
 
@@ -80,7 +80,7 @@ class Platform {
   bool has_focus_ = false;
   bool should_exit_ = false;
 
-  std::unique_ptr<AudioDriver> audio_driver_;
+  std::unique_ptr<Audio> audio_;
   std::unique_ptr<Renderer> renderer_;
   std::unique_ptr<Engine> engine_;
 

src/engine/platform/platform_android.cc

@@ -6,6 +6,7 @@
 
 #include "base/log.h"
 #include "base/task_runner.h"
+#include "engine/audio/audio.h"
 #include "engine/engine.h"
 #include "engine/input_event.h"
 #include "engine/renderer/renderer.h"

src/engine/platform/platform_linux.cc

@@ -3,6 +3,7 @@
 #include "base/log.h"
 #include "base/task_runner.h"
 #include "base/vecmath.h"
+#include "engine/audio/audio.h"
 #include "engine/engine.h"
 #include "engine/input_event.h"
 #include "engine/renderer/renderer.h"

src/engine/sound_player.cc

@@ -2,7 +2,7 @@
 
 #include "base/interpolation.h"
 #include "base/log.h"
-#include "engine/audio/audio_mixer.h"
+#include "engine/audio/audio.h"
 #include "engine/engine.h"
 #include "engine/sound.h"
 
@@ -11,10 +11,10 @@ using namespace base;
 namespace eng {
 
 SoundPlayer::SoundPlayer()
-    : resource_id_(Engine::Get().GetAudioMixer()->CreateResource()) {}
+    : resource_id_(Engine::Get().GetAudio()->CreateResource()) {}
 
 SoundPlayer::~SoundPlayer() {
-  Engine::Get().GetAudioMixer()->DestroyResource(resource_id_);
+  Engine::Get().GetAudio()->DestroyResource(resource_id_);
 }
 
 void SoundPlayer::SetSound(std::shared_ptr<Sound> sound) {
@@ -32,14 +32,14 @@ void SoundPlayer::Play(bool loop, float fade_in_duration) {
     return;
 
   int step = variate_ ? Engine::Get().GetRandomGenerator().Roll(3) - 2 : 0;
-  Engine::Get().GetAudioMixer()->SetResampleStep(resource_id_, step * 12);
-  Engine::Get().GetAudioMixer()->SetLoop(resource_id_, loop);
+  Engine::Get().GetAudio()->SetResampleStep(resource_id_, step * 12);
+  Engine::Get().GetAudio()->SetLoop(resource_id_, loop);
   if (fade_in_duration > 0)
-    Engine::Get().GetAudioMixer()->SetAmplitudeInc(
+    Engine::Get().GetAudio()->SetAmplitudeInc(
         resource_id_, 1.0f / (sound_->sample_rate() * fade_in_duration));
   else
-    Engine::Get().GetAudioMixer()->SetAmplitudeInc(resource_id_, 0);
-  Engine::Get().GetAudioMixer()->Play(
+    Engine::Get().GetAudio()->SetAmplitudeInc(resource_id_, 0);
+  Engine::Get().GetAudio()->Play(
       resource_id_, sound_, fade_in_duration > 0 ? 0 : max_amplitude_, true);
 }
 
@@ -48,10 +48,10 @@ void SoundPlayer::Resume(float fade_in_duration) {
     return;
 
   if (fade_in_duration > 0)
-    Engine::Get().GetAudioMixer()->SetAmplitudeInc(
+    Engine::Get().GetAudio()->SetAmplitudeInc(
         resource_id_, 1.0f / (sound_->sample_rate() * fade_in_duration));
-  Engine::Get().GetAudioMixer()->Play(resource_id_, sound_,
-                                      fade_in_duration > 0 ? 0 : -1, false);
+  Engine::Get().GetAudio()->Play(resource_id_, sound_,
+                                 fade_in_duration > 0 ? 0 : -1, false);
 }
 
 void SoundPlayer::Stop(float fade_out_duration) {
@@ -59,10 +59,10 @@ void SoundPlayer::Stop(float fade_out_duration) {
     return;
 
   if (fade_out_duration > 0)
-    Engine::Get().GetAudioMixer()->SetAmplitudeInc(
+    Engine::Get().GetAudio()->SetAmplitudeInc(
         resource_id_, -1.0f / (sound_->sample_rate() * fade_out_duration));
   else
-    Engine::Get().GetAudioMixer()->Stop(resource_id_);
+    Engine::Get().GetAudio()->Stop(resource_id_);
 }
 
 void SoundPlayer::SetVariate(bool variate) {
@@ -70,16 +70,16 @@ void SoundPlayer::SetVariate(bool variate) {
 }
 
 void SoundPlayer::SetSimulateStereo(bool simulate) {
-  Engine::Get().GetAudioMixer()->SetSimulateStereo(resource_id_, simulate);
+  Engine::Get().GetAudio()->SetSimulateStereo(resource_id_, simulate);
 }
 
 void SoundPlayer::SetMaxAplitude(float max_amplitude) {
   max_amplitude_ = max_amplitude;
-  Engine::Get().GetAudioMixer()->SetMaxAmplitude(resource_id_, max_amplitude);
+  Engine::Get().GetAudio()->SetMaxAmplitude(resource_id_, max_amplitude);
 }
 
 void SoundPlayer::SetEndCallback(base::Closure cb) {
-  Engine::Get().GetAudioMixer()->SetEndCallback(resource_id_, cb);
+  Engine::Get().GetAudio()->SetEndCallback(resource_id_, cb);
 }
 
 }  // namespace eng