services/surfaceflinger/tests/BufferGenerator.cpp - android_frameworks_native - Gitiles

 /*
  * Copyright 2018 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *      http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 // TODO(b/129481165): remove the #pragma below and fix conversion issues
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wconversion"

 #include <gui/BufferItemConsumer.h>
 #include <gui/Surface.h>

 #include <GLES3/gl3.h>
 #include <math/vec2.h>
 #include <math/vec3.h>
 #include <math/vec4.h>

 #include "BufferGenerator.h"
 #include "BufferGeneratorShader.h"

 namespace android {

 /* Used to receive the surfaces and fences from egl. The egl buffers are thrown
  * away. The fences are sent to the requester via a callback */
 class SurfaceManager {
 public:
     /* Returns a fence from egl */
     using BufferCallback = std::function<void(const sp<GraphicBuffer>& buffer, int32_t fence)>;

     /* Listens for a new frame, detaches the buffer and returns the fence
      * through saved callback. */
     class BufferListener : public ConsumerBase::FrameAvailableListener {
     public:
         BufferListener(sp<IGraphicBufferConsumer> consumer, BufferCallback callback)
               : mConsumer(consumer), mCallback(callback) {}

         void onFrameAvailable(const BufferItem& /*item*/) {
             BufferItem item;

             if (mConsumer->acquireBuffer(&item, 0)) return;
             if (mConsumer->detachBuffer(item.mSlot)) return;

             mCallback(item.mGraphicBuffer, item.mFence->dup());
         }

     private:
         sp<IGraphicBufferConsumer> mConsumer;
         BufferCallback mCallback;
     };

     /* Creates a buffer listener that waits on a new frame from the buffer
      * queue. */
     void initialize(uint32_t width, uint32_t height, android_pixel_format_t format,
                     BufferCallback callback) {
         sp<IGraphicBufferProducer> producer;
         sp<IGraphicBufferConsumer> consumer;
         BufferQueue::createBufferQueue(&producer, &consumer);

         consumer->setDefaultBufferSize(width, height);
         consumer->setDefaultBufferFormat(format);

         mBufferItemConsumer =
                 sp<BufferItemConsumer>::make(consumer, GraphicBuffer::USAGE_HW_TEXTURE);

         mListener = sp<BufferListener>::make(consumer, callback);
         mBufferItemConsumer->setFrameAvailableListener(mListener);

         mSurface = sp<Surface>::make(producer, true);
     }

     /* Used by Egl manager. The surface is never displayed. */
     sp<Surface> getSurface() const { return mSurface; }

 private:
     sp<BufferItemConsumer> mBufferItemConsumer;
     sp<BufferListener> mListener;
     /* Used by Egl manager. The surface is never displayed */
     sp<Surface> mSurface;
 };

 /* Used to generate valid fences. It is not possible to create a placeholder sync
  * fence for testing. Egl can generate buffers along with a valid fence.
  * The buffer cannot be guaranteed to be the same format across all devices so
  * a CPU filled buffer is used instead. The Egl fence is used along with the
  * CPU filled buffer. */
 class EglManager {
 public:
     EglManager()
           : mEglDisplay(EGL_NO_DISPLAY), mEglSurface(EGL_NO_SURFACE), mEglContext(EGL_NO_CONTEXT) {}

     ~EglManager() { cleanup(); }

     int initialize(sp<Surface> surface) {
         mSurface = surface;

         mEglDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
         if (mEglDisplay == EGL_NO_DISPLAY) return false;

         EGLint major;
         EGLint minor;
         if (!eglInitialize(mEglDisplay, &major, &minor)) {
             ALOGW("Could not initialize EGL");
             return false;
         }

         /* We're going to use a 1x1 pbuffer surface later on
          * The configuration distance doesn't really matter for what we're
          * trying to do */
         EGLint configAttrs[] = {EGL_RENDERABLE_TYPE,
                                 EGL_OPENGL_ES2_BIT,
                                 EGL_RED_SIZE,
                                 8,
                                 EGL_GREEN_SIZE,
                                 8,
                                 EGL_BLUE_SIZE,
                                 8,
                                 EGL_ALPHA_SIZE,
                                 0,
                                 EGL_DEPTH_SIZE,
                                 24,
                                 EGL_STENCIL_SIZE,
                                 0,
                                 EGL_NONE};

         EGLConfig configs[1];
         EGLint configCnt;
         if (!eglChooseConfig(mEglDisplay, configAttrs, configs, 1, &configCnt)) {
             ALOGW("Could not select EGL configuration");
             eglReleaseThread();
             eglTerminate(mEglDisplay);
             return false;
         }

         if (configCnt <= 0) {
             ALOGW("Could not find EGL configuration");
             eglReleaseThread();
             eglTerminate(mEglDisplay);
             return false;
         }

         /* These objects are initialized below but the default "null" values are
          * used to cleanup properly at any point in the initialization sequence */
         EGLint attrs[] = {EGL_CONTEXT_CLIENT_VERSION, 3, EGL_NONE};
         mEglContext = eglCreateContext(mEglDisplay, configs[0], EGL_NO_CONTEXT, attrs);
         if (mEglContext == EGL_NO_CONTEXT) {
             ALOGW("Could not create EGL context");
             cleanup();
             return false;
         }

         EGLint majorVersion;
         if (!eglQueryContext(mEglDisplay, mEglContext, EGL_CONTEXT_CLIENT_VERSION, &majorVersion)) {
             ALOGW("Could not query EGL version");
             cleanup();
             return false;
         }

         if (majorVersion != 3) {
             ALOGW("Unsupported EGL version");
             cleanup();
             return false;
         }

         EGLint surfaceAttrs[] = {EGL_NONE};
         mEglSurface = eglCreateWindowSurface(mEglDisplay, configs[0], mSurface.get(), surfaceAttrs);
         if (mEglSurface == EGL_NO_SURFACE) {
             ALOGW("Could not create EGL surface");
             cleanup();
             return false;
         }

         if (!eglMakeCurrent(mEglDisplay, mEglSurface, mEglSurface, mEglContext)) {
             ALOGW("Could not change current EGL context");
             cleanup();
             return false;
         }

         return true;
     }

     void makeCurrent() const { eglMakeCurrent(mEglDisplay, mEglSurface, mEglSurface, mEglContext); }

     void present() const { eglSwapBuffers(mEglDisplay, mEglSurface); }

 private:
     void cleanup() {
         if (mEglDisplay == EGL_NO_DISPLAY) return;
         if (mEglSurface != EGL_NO_SURFACE) eglDestroySurface(mEglDisplay, mEglSurface);
         if (mEglContext != EGL_NO_CONTEXT) eglDestroyContext(mEglDisplay, mEglContext);

         eglMakeCurrent(mEglDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
         eglReleaseThread();
         eglTerminate(mEglDisplay);
     }

     sp<Surface> mSurface;
     EGLDisplay mEglDisplay;
     EGLSurface mEglSurface;
     EGLContext mEglContext;
 };

 class Program {
 public:
     ~Program() {
         if (mInitialized) {
             glDetachShader(mProgram, mVertexShader);
             glDetachShader(mProgram, mFragmentShader);

             glDeleteShader(mVertexShader);
             glDeleteShader(mFragmentShader);

             glDeleteProgram(mProgram);
         }
     }

     bool initialize(const char* vertex, const char* fragment) {
         mVertexShader = buildShader(vertex, GL_VERTEX_SHADER);
         if (!mVertexShader) {
             return false;
         }

         mFragmentShader = buildShader(fragment, GL_FRAGMENT_SHADER);
         if (!mFragmentShader) {
             return false;
         }

         mProgram = glCreateProgram();
         glAttachShader(mProgram, mVertexShader);
         glAttachShader(mProgram, mFragmentShader);

         glLinkProgram(mProgram);

         GLint status;
         glGetProgramiv(mProgram, GL_LINK_STATUS, &status);
         if (status != GL_TRUE) {
             GLint length = 0;
             glGetProgramiv(mProgram, GL_INFO_LOG_LENGTH, &length);
             if (length > 1) {
                 GLchar log[length];
                 glGetProgramInfoLog(mProgram, length, nullptr, &log[0]);
                 ALOGE("%s", log);
             }
             ALOGE("Error while linking shaders");
             return false;
         }
         mInitialized = true;
         return true;
     }

     void use() const { glUseProgram(mProgram); }

     void bindVec4(GLint location, vec4 v) const { glUniform4f(location, v.x, v.y, v.z, v.w); }

     void bindVec3(GLint location, const vec3* v, uint32_t count) const {
         glUniform3fv(location, count, &(v->x));
     }

     void bindFloat(GLint location, float v) { glUniform1f(location, v); }

 private:
     GLuint buildShader(const char* source, GLenum type) const {
         GLuint shader = glCreateShader(type);
         glShaderSource(shader, 1, &source, nullptr);
         glCompileShader(shader);

         GLint status;
         glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
         if (status != GL_TRUE) {
             ALOGE("Error while compiling shader of type 0x%x:\n===\n%s\n===", type, source);
             // Some drivers return wrong values for GL_INFO_LOG_LENGTH
             // use a fixed size instead
             GLchar log[512];
             glGetShaderInfoLog(shader, sizeof(log), nullptr, &log[0]);
             ALOGE("Shader info log: %s", log);
             return 0;
         }

         return shader;
     }

     GLuint mProgram = 0;
     GLuint mVertexShader = 0;
     GLuint mFragmentShader = 0;
     bool mInitialized = false;
 };

 BufferGenerator::BufferGenerator()
       : mSurfaceManager(new SurfaceManager), mEglManager(new EglManager), mProgram(new Program) {
     mBufferSize.set(1000.0, 1000.0);

     auto setBufferWithContext =
             std::bind(setBuffer, std::placeholders::_1, std::placeholders::_2, this);
     mSurfaceManager->initialize(mBufferSize.width, mBufferSize.height, HAL_PIXEL_FORMAT_RGBA_8888,
                                 setBufferWithContext);

     if (!mEglManager->initialize(mSurfaceManager->getSurface())) return;

     mEglManager->makeCurrent();

     if (!mProgram->initialize(VERTEX_SHADER, FRAGMENT_SHADER)) return;
     mProgram->use();
     mProgram->bindVec4(0,
                        vec4{mBufferSize.width, mBufferSize.height, 1.0f / mBufferSize.width,
                             1.0f / mBufferSize.height});
     mProgram->bindVec3(2, &SPHERICAL_HARMONICS[0], 4);

     glEnableVertexAttribArray(0);
     glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, &TRIANGLE[0]);

     mInitialized = true;
 }

 BufferGenerator::~BufferGenerator() {
     mEglManager->makeCurrent();
 }

 status_t BufferGenerator::get(sp<GraphicBuffer>* outBuffer, sp<Fence>* outFence) {
     // mMutex is used to protect get() from getting called by multiple threads at the same time
     static std::mutex mMutex;
     std::lock_guard lock(mMutex);

     if (!mInitialized) {
         if (outBuffer) {
             *outBuffer = nullptr;
         }
         if (*outFence) {
             *outFence = nullptr;
         }
         return -EINVAL;
     }

     // Generate a buffer and fence. They will be returned through the setBuffer callback
     mEglManager->makeCurrent();

     glClear(GL_COLOR_BUFFER_BIT);

     const std::chrono::duration<float> time = std::chrono::steady_clock::now() - mEpoch;
     mProgram->bindFloat(1, time.count());

     glDrawArrays(GL_TRIANGLES, 0, 3);

     mPending = true;
     mEglManager->present();

     // Wait for the setBuffer callback
     if (!mConditionVariable.wait_for(mMutex, std::chrono::seconds(2),
                                      [this] { return !mPending; })) {
         ALOGE("failed to set buffer and fence");
         return -ETIME;
     }

     // Return buffer and fence
     if (outBuffer) {
         *outBuffer = mGraphicBuffer;
     }
     if (outFence) {
         *outFence = sp<Fence>::make(mFence);
     } else {
         close(mFence);
     }
     mGraphicBuffer = nullptr;
     mFence = -1;

     return NO_ERROR;
 }

 ui::Size BufferGenerator::getSize() {
     return mBufferSize;
 }

 // static
 void BufferGenerator::setBuffer(const sp<GraphicBuffer>& buffer, int32_t fence,
                                 void* bufferGenerator) {
     BufferGenerator* generator = static_cast<BufferGenerator*>(bufferGenerator);
     generator->mGraphicBuffer = buffer;
     generator->mFence = fence;
     generator->mPending = false;
     generator->mConditionVariable.notify_all();
 }

 } // namespace android

 // TODO(b/129481165): remove the #pragma below and fix conversion issues
 #pragma clang diagnostic pop // ignored "-Wconversion"
	/*
	* Copyright 2018 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	// TODO(b/129481165): remove the #pragma below and fix conversion issues
	#pragma clang diagnostic push
	#pragma clang diagnostic ignored "-Wconversion"

	#include <gui/BufferItemConsumer.h>
	#include <gui/Surface.h>

	#include <GLES3/gl3.h>
	#include <math/vec2.h>
	#include <math/vec3.h>
	#include <math/vec4.h>

	#include "BufferGenerator.h"
	#include "BufferGeneratorShader.h"

	namespace android {

	/* Used to receive the surfaces and fences from egl. The egl buffers are thrown
	* away. The fences are sent to the requester via a callback */
	class SurfaceManager {
	public:
	/* Returns a fence from egl */
	using BufferCallback = std::function<void(const sp<GraphicBuffer>& buffer, int32_t fence)>;

	/* Listens for a new frame, detaches the buffer and returns the fence
	* through saved callback. */
	class BufferListener : public ConsumerBase::FrameAvailableListener {
	public:
	BufferListener(sp<IGraphicBufferConsumer> consumer, BufferCallback callback)
	: mConsumer(consumer), mCallback(callback) {}

	void onFrameAvailable(const BufferItem& /item/) {
	BufferItem item;

	if (mConsumer->acquireBuffer(&item, 0)) return;
	if (mConsumer->detachBuffer(item.mSlot)) return;

	mCallback(item.mGraphicBuffer, item.mFence->dup());
	}

	private:
	sp<IGraphicBufferConsumer> mConsumer;
	BufferCallback mCallback;
	};

	/* Creates a buffer listener that waits on a new frame from the buffer
	* queue. */
	void initialize(uint32_t width, uint32_t height, android_pixel_format_t format,
	BufferCallback callback) {
	sp<IGraphicBufferProducer> producer;
	sp<IGraphicBufferConsumer> consumer;
	BufferQueue::createBufferQueue(&producer, &consumer);

	consumer->setDefaultBufferSize(width, height);
	consumer->setDefaultBufferFormat(format);

	mBufferItemConsumer =
	sp<BufferItemConsumer>::make(consumer, GraphicBuffer::USAGE_HW_TEXTURE);

	mListener = sp<BufferListener>::make(consumer, callback);
	mBufferItemConsumer->setFrameAvailableListener(mListener);

	mSurface = sp<Surface>::make(producer, true);
	}

	/* Used by Egl manager. The surface is never displayed. */
	sp<Surface> getSurface() const { return mSurface; }

	private:
	sp<BufferItemConsumer> mBufferItemConsumer;
	sp<BufferListener> mListener;
	/* Used by Egl manager. The surface is never displayed */
	sp<Surface> mSurface;
	};

	/* Used to generate valid fences. It is not possible to create a placeholder sync
	* fence for testing. Egl can generate buffers along with a valid fence.
	* The buffer cannot be guaranteed to be the same format across all devices so
	* a CPU filled buffer is used instead. The Egl fence is used along with the
	* CPU filled buffer. */
	class EglManager {
	public:
	EglManager()
	: mEglDisplay(EGL_NO_DISPLAY), mEglSurface(EGL_NO_SURFACE), mEglContext(EGL_NO_CONTEXT) {}

	~EglManager() { cleanup(); }

	int initialize(sp<Surface> surface) {
	mSurface = surface;

	mEglDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);
	if (mEglDisplay == EGL_NO_DISPLAY) return false;

	EGLint major;
	EGLint minor;
	if (!eglInitialize(mEglDisplay, &major, &minor)) {
	ALOGW("Could not initialize EGL");
	return false;
	}

	/* We're going to use a 1x1 pbuffer surface later on
	* The configuration distance doesn't really matter for what we're
	* trying to do */
	EGLint configAttrs[] = {EGL_RENDERABLE_TYPE,
	EGL_OPENGL_ES2_BIT,
	EGL_RED_SIZE,
	8,
	EGL_GREEN_SIZE,
	8,
	EGL_BLUE_SIZE,
	8,
	EGL_ALPHA_SIZE,
	0,
	EGL_DEPTH_SIZE,
	24,
	EGL_STENCIL_SIZE,
	0,
	EGL_NONE};

	EGLConfig configs[1];
	EGLint configCnt;
	if (!eglChooseConfig(mEglDisplay, configAttrs, configs, 1, &configCnt)) {
	ALOGW("Could not select EGL configuration");
	eglReleaseThread();
	eglTerminate(mEglDisplay);
	return false;
	}

	if (configCnt <= 0) {
	ALOGW("Could not find EGL configuration");
	eglReleaseThread();
	eglTerminate(mEglDisplay);
	return false;
	}

	/* These objects are initialized below but the default "null" values are
	* used to cleanup properly at any point in the initialization sequence */
	EGLint attrs[] = {EGL_CONTEXT_CLIENT_VERSION, 3, EGL_NONE};
	mEglContext = eglCreateContext(mEglDisplay, configs[0], EGL_NO_CONTEXT, attrs);
	if (mEglContext == EGL_NO_CONTEXT) {
	ALOGW("Could not create EGL context");
	cleanup();
	return false;
	}

	EGLint majorVersion;
	if (!eglQueryContext(mEglDisplay, mEglContext, EGL_CONTEXT_CLIENT_VERSION, &majorVersion)) {
	ALOGW("Could not query EGL version");
	cleanup();
	return false;
	}

	if (majorVersion != 3) {
	ALOGW("Unsupported EGL version");
	cleanup();
	return false;
	}

	EGLint surfaceAttrs[] = {EGL_NONE};
	mEglSurface = eglCreateWindowSurface(mEglDisplay, configs[0], mSurface.get(), surfaceAttrs);
	if (mEglSurface == EGL_NO_SURFACE) {
	ALOGW("Could not create EGL surface");
	cleanup();
	return false;
	}

	if (!eglMakeCurrent(mEglDisplay, mEglSurface, mEglSurface, mEglContext)) {
	ALOGW("Could not change current EGL context");
	cleanup();
	return false;
	}

	return true;
	}

	void makeCurrent() const { eglMakeCurrent(mEglDisplay, mEglSurface, mEglSurface, mEglContext); }

	void present() const { eglSwapBuffers(mEglDisplay, mEglSurface); }

	private:
	void cleanup() {
	if (mEglDisplay == EGL_NO_DISPLAY) return;
	if (mEglSurface != EGL_NO_SURFACE) eglDestroySurface(mEglDisplay, mEglSurface);
	if (mEglContext != EGL_NO_CONTEXT) eglDestroyContext(mEglDisplay, mEglContext);

	eglMakeCurrent(mEglDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
	eglReleaseThread();
	eglTerminate(mEglDisplay);
	}

	sp<Surface> mSurface;
	EGLDisplay mEglDisplay;
	EGLSurface mEglSurface;
	EGLContext mEglContext;
	};

	class Program {
	public:
	~Program() {
	if (mInitialized) {
	glDetachShader(mProgram, mVertexShader);
	glDetachShader(mProgram, mFragmentShader);

	glDeleteShader(mVertexShader);
	glDeleteShader(mFragmentShader);

	glDeleteProgram(mProgram);
	}
	}

	bool initialize(const char* vertex, const char* fragment) {
	mVertexShader = buildShader(vertex, GL_VERTEX_SHADER);
	if (!mVertexShader) {
	return false;
	}

	mFragmentShader = buildShader(fragment, GL_FRAGMENT_SHADER);
	if (!mFragmentShader) {
	return false;
	}

	mProgram = glCreateProgram();
	glAttachShader(mProgram, mVertexShader);
	glAttachShader(mProgram, mFragmentShader);

	glLinkProgram(mProgram);

	GLint status;
	glGetProgramiv(mProgram, GL_LINK_STATUS, &status);
	if (status != GL_TRUE) {
	GLint length = 0;
	glGetProgramiv(mProgram, GL_INFO_LOG_LENGTH, &length);
	if (length > 1) {
	GLchar log[length];
	glGetProgramInfoLog(mProgram, length, nullptr, &log[0]);
	ALOGE("%s", log);
	}
	ALOGE("Error while linking shaders");
	return false;
	}
	mInitialized = true;
	return true;
	}

	void use() const { glUseProgram(mProgram); }

	void bindVec4(GLint location, vec4 v) const { glUniform4f(location, v.x, v.y, v.z, v.w); }

	void bindVec3(GLint location, const vec3* v, uint32_t count) const {
	glUniform3fv(location, count, &(v->x));
	}

	void bindFloat(GLint location, float v) { glUniform1f(location, v); }

	private:
	GLuint buildShader(const char* source, GLenum type) const {
	GLuint shader = glCreateShader(type);
	glShaderSource(shader, 1, &source, nullptr);
	glCompileShader(shader);

	GLint status;
	glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
	if (status != GL_TRUE) {
	ALOGE("Error while compiling shader of type 0x%x:\n===\n%s\n===", type, source);
	// Some drivers return wrong values for GL_INFO_LOG_LENGTH
	// use a fixed size instead
	GLchar log[512];
	glGetShaderInfoLog(shader, sizeof(log), nullptr, &log[0]);
	ALOGE("Shader info log: %s", log);
	return 0;
	}

	return shader;
	}

	GLuint mProgram = 0;
	GLuint mVertexShader = 0;
	GLuint mFragmentShader = 0;
	bool mInitialized = false;
	};

	BufferGenerator::BufferGenerator()
	: mSurfaceManager(new SurfaceManager), mEglManager(new EglManager), mProgram(new Program) {
	mBufferSize.set(1000.0, 1000.0);

	auto setBufferWithContext =
	std::bind(setBuffer, std::placeholders::_1, std::placeholders::_2, this);
	mSurfaceManager->initialize(mBufferSize.width, mBufferSize.height, HAL_PIXEL_FORMAT_RGBA_8888,
	setBufferWithContext);

	if (!mEglManager->initialize(mSurfaceManager->getSurface())) return;

	mEglManager->makeCurrent();

	if (!mProgram->initialize(VERTEX_SHADER, FRAGMENT_SHADER)) return;
	mProgram->use();
	mProgram->bindVec4(0,
	vec4{mBufferSize.width, mBufferSize.height, 1.0f / mBufferSize.width,
	1.0f / mBufferSize.height});
	mProgram->bindVec3(2, &SPHERICAL_HARMONICS[0], 4);

	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, &TRIANGLE[0]);

	mInitialized = true;
	}

	BufferGenerator::~BufferGenerator() {
	mEglManager->makeCurrent();
	}

	status_t BufferGenerator::get(sp<GraphicBuffer>* outBuffer, sp<Fence>* outFence) {
	// mMutex is used to protect get() from getting called by multiple threads at the same time
	static std::mutex mMutex;
	std::lock_guard lock(mMutex);

	if (!mInitialized) {
	if (outBuffer) {
	*outBuffer = nullptr;
	}
	if (*outFence) {
	*outFence = nullptr;
	}
	return -EINVAL;
	}

	// Generate a buffer and fence. They will be returned through the setBuffer callback
	mEglManager->makeCurrent();

	glClear(GL_COLOR_BUFFER_BIT);

	const std::chrono::duration<float> time = std::chrono::steady_clock::now() - mEpoch;
	mProgram->bindFloat(1, time.count());

	glDrawArrays(GL_TRIANGLES, 0, 3);

	mPending = true;
	mEglManager->present();

	// Wait for the setBuffer callback
	if (!mConditionVariable.wait_for(mMutex, std::chrono::seconds(2),
	[this] { return !mPending; })) {
	ALOGE("failed to set buffer and fence");
	return -ETIME;
	}

	// Return buffer and fence
	if (outBuffer) {
	*outBuffer = mGraphicBuffer;
	}
	if (outFence) {
	*outFence = sp<Fence>::make(mFence);
	} else {
	close(mFence);
	}
	mGraphicBuffer = nullptr;
	mFence = -1;

	return NO_ERROR;
	}

	ui::Size BufferGenerator::getSize() {
	return mBufferSize;
	}

	// static
	void BufferGenerator::setBuffer(const sp<GraphicBuffer>& buffer, int32_t fence,
	void* bufferGenerator) {
	BufferGenerator* generator = static_cast<BufferGenerator*>(bufferGenerator);
	generator->mGraphicBuffer = buffer;
	generator->mFence = fence;
	generator->mPending = false;
	generator->mConditionVariable.notify_all();
	}

	} // namespace android

	// TODO(b/129481165): remove the #pragma below and fix conversion issues
	#pragma clang diagnostic pop // ignored "-Wconversion"