Android OpenGL ES - EGL C++实现

PS
本篇继续上一篇的内容，我们来对Native EGL环境实现的各个步骤进行详细解析

EGL Native层的实现

上一篇文章Android OpenGL ES - EGL源码解析以及C++实现

我们还是先来回顾一下流程图

以及代码

 //(1) 将线程附加到虚拟机，并获取env
     if (that->m_jvm_for_thread->AttachCurrentThread(&env, NULL) != JNI_OK) {
            LOGE(that->TAG, "线程初始化异常");
            return; 
     }
     // (2) 初始化 EGL 
    if (!that->InitEGL()) {
         //解除线程和jvm关联
         that->m_jvm_for_thread->DetachCurrentThread();
         return; 
     }
     
     //进入循环
    while (true) {
            //根据OpenGL渲染状态进入不同的处理
            switch (that->m_state) {
                //刷新Surface，从外面设置Surface后m_state置为该状态，说明已经从外部(java层)获得Surface的对象了
                case FRESH_SURFACE:
                     LOGI(that->TAG, "Loop Render FRESH_SURFACE")
                     // (3) 初始化Window
                     that->InitDspWindow(env);
                     // (4) 创建EglSurface
                     that->CreateSurface();
                     // m_state置为RENDERING状态进入渲染
                     that->m_state = RENDERING;
                     break; 
                 case RENDERING:
                    LOGI(that->TAG, "Loop Render RENDERING")
                    // (5) 渲染
                    that->Render();
                    break; 
               
                 case STOP:
                    LOGI(that->TAG, "Loop Render STOP")
                    //(6) 解除线程和jvm关联
                     that->ReleaseRender();
                     that->m_jvm_for_thread->DetachCurrentThread();
                     return; 
                case SURFACE_DESTROY:
                    LOGI(that->TAG, "Loop Render SURFACE_DESTROY")
                    //(7) 释放资源
                    that->DestroySurface();
                    that->m_state = NO_SURFACE;
                    break; 
                case NO_SURFACE:
                default:
                    break;
     }
    usleep(20000);
 }
}

首先第(1)步将线程附加到虚拟机，并获取env,这一步简单明了，我们从第(2)步开始

EGL封装准备

我们在上一篇就知道了EGL的一些基础知识，EGLDiaplay,EGLConfig,EGLSurface,EGLContext，我们需要把这些基础类进行封装，那么如何进行封装呢，我们先看一下对于我们上篇文章中自定义的GLRender类需要什么
gl_render.h

//Surface引用，必须要使用引用，否则无法在线程中操作
jobject m_surface_ref = NULL;
//本地屏幕
ANativeWindow *m_native_window = NULL;
//EGL显示表面 注意这里是我们自定义的EglSurface包装类而不是系统提供的EGLSurface哦
EglSurface *m_egl_surface = NULL;

对于gl_render来说输入的是外部的Surface对象，我们这里的是jobject m_surface_ref,那么输出需要的是ANativeWindow,EglSurface

关于 ANativeWindow可以查看官方文档 ANativeWindow

那么EglSurface呢，

egl_surface.h

class EglSurface {
private:
    const char *TAG = "EglSurface";
    //本地屏幕
     ANativeWindow *m_native_window = NULL;
     //封装了EGLDisplay EGLConfig EGLContext的自定义类
     EglCore *m_core;
     //EGL API提供的 EGLSurface
     EGLSurface m_surface;
}

可以看到我们上面的定义的思想也是V(View)和C(Controller)进行了分离。

egl_core.h

class EglCore {
private:
    const char *TAG = "EglCore";
     //EGL显示窗口
     EGLDisplay m_egl_dsp = EGL_NO_DISPLAY;
     //EGL上下文
     EGLContext m_egl_context = EGL_NO_CONTEXT;
     //EGL配置
     EGLConfig m_egl_config;
}

有了上面的准备工作后，我们就跟着流程图的步骤来一步步走

(2)初始化EGL

gl_render.cpp

bool GLRender::InitEGL() {
    //创建EglSurface对象
    m_egl_surface = new EglSurface();
    //调用EglSurface的init方法
    return m_egl_surface->Init();
}

egl_surface.cpp

PS
我们上面也说了EGL的初始化主要是对EGLDisplay EGLConfig EGLContext的操作，所以现在是对EGLCore的操作

EglSurface::EglSurface() {
    //创建EGLCore
    m_core = new EglCore();
}

bool EglSurface::Init() {
    //调用EGLCore的init方法
    return m_core->Init(NULL);
}

egl_core.cpp

EglCore::EglCore() {
}


bool EglCore::Init(EGLContext share_ctx) {
    if (m_egl_dsp != EGL_NO_DISPLAY) {
        LOGE(TAG, "EGL already set up")
        return true;
     }
    if (share_ctx == NULL) {
            share_ctx = EGL_NO_CONTEXT;
     }
     //获取Dispaly
    m_egl_dsp = eglGetDisplay(EGL_DEFAULT_DISPLAY);
     if (m_egl_dsp == EGL_NO_DISPLAY || eglGetError() != EGL_SUCCESS) {
            LOGE(TAG, "EGL init display fail")
            return false;
     }
        EGLint major_ver, minor_ver;
     //初始化egl
     EGLBoolean success = eglInitialize(m_egl_dsp, &major_ver, &minor_ver);
     if (success != EGL_TRUE || eglGetError() != EGL_SUCCESS) {
            LOGE(TAG, "EGL init fail")
            return false;
     }
        LOGI(TAG, "EGL version: %d.%d", major_ver, minor_ver)
     //获取EGLConfig   
     m_egl_config = GetEGLConfig();
     const EGLint attr[] = {EGL_CONTEXT_CLIENT_VERSION, 2, EGL_NONE};
     //创建EGLContext
     m_egl_context = eglCreateContext(m_egl_dsp, m_egl_config, share_ctx, attr);
     if (m_egl_context == EGL_NO_CONTEXT) {
            LOGE(TAG, "EGL create fail, error is %x", eglGetError());
     return false; }
        EGLint egl_format;
     success = eglGetConfigAttrib(m_egl_dsp, m_egl_config, EGL_NATIVE_VISUAL_ID, &egl_format);
     if (success != EGL_TRUE || eglGetError() != EGL_SUCCESS) {
            LOGE(TAG, "EGL get config fail, error is %x", eglGetError())
            return false;
     }
    LOGI(TAG, "EGL init success")
    return true;
}

EGLConfig EglCore::GetEGLConfig() {
    EGLint numConfigs;
    EGLConfig config;

    //希望的最小配置，
    static const EGLint CONFIG_ATTRIBS[] = {
            EGL_BUFFER_SIZE, EGL_DONT_CARE,
            EGL_RED_SIZE, 8,//R 位数
            EGL_GREEN_SIZE, 8,//G 位数
            EGL_BLUE_SIZE, 8,//B 位数
            EGL_ALPHA_SIZE, 8,//A 位数
            EGL_DEPTH_SIZE, 16,//深度
            EGL_STENCIL_SIZE, EGL_DONT_CARE,
            EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
            EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
            EGL_NONE // the end 结束标志
    };
    //根据你所设定的最小配置系统会选择一个满足你最低要求的配置，这个真正的配置往往要比你期望的属性更多
    EGLBoolean success = eglChooseConfig(m_egl_dsp, CONFIG_ATTRIBS, &config, 1, &numConfigs);
    if (!success || eglGetError() != EGL_SUCCESS) {
        LOGE(TAG, "EGL config fail")
        return NULL;
    }
    return config;
}

（3）创建Window

gl_render.cpp

void GLRender::InitDspWindow(JNIEnv *env) {
    //传进来的Surface对象的引用
    if (m_surface_ref != NULL) {
        // 初始化窗口
        m_native_window = ANativeWindow_fromSurface(env, m_surface_ref);

        // 绘制区域的宽高
        m_window_width = ANativeWindow_getWidth(m_native_window);
        m_window_height = ANativeWindow_getHeight(m_native_window);

        //设置宽高限制缓冲区中的像素数量
        ANativeWindow_setBuffersGeometry(m_native_window, m_window_width,
                                         m_window_height, WINDOW_FORMAT_RGBA_8888);

        LOGD(TAG, "View Port width: %d, height: %d", m_window_width, m_window_height)
    }
}

(4)创建EglSurface并绑定到线程

gl_render.cpp

void GLRender::CreateSurface() {
    m_egl_surface->CreateEglSurface(m_native_window, m_window_width, m_window_height);
    glViewport(0, 0, m_window_width, m_window_height);
}

egl_surface.cpp

/**
 * 
 * @param native_window 传入上一步创建的ANativeWindow
 * @param width 
 * @param height 
 */
void EglSurface::CreateEglSurface(ANativeWindow *native_window, int width, int height) {
    if (native_window != NULL) {
        this->m_native_window = native_window;
        m_surface = m_core->CreateWindSurface(m_native_window);
    } else {
        m_surface = m_core->CreateOffScreenSurface(width, height);
    }
    if (m_surface == NULL) {
        LOGE(TAG, "EGL create window surface fail")
        Release();
    }
    MakeCurrent();
}

void EglSurface::MakeCurrent() {
    m_core->MakeCurrent(m_surface);
}

egl_core.cpp

EGLSurface EglCore::CreateWindSurface(ANativeWindow *window) {
    //调用EGL Native API创建Window Surface
    EGLSurface surface = eglCreateWindowSurface(m_egl_dsp, m_egl_config, window, 0);
    if (eglGetError() != EGL_SUCCESS) {
        LOGI(TAG, "EGL create window surface fail")
        return NULL;
    }
    return surface;
}

void EglCore::MakeCurrent(EGLSurface egl_surface) {
    //调用EGL Native API 绑定渲染环境到当前线程
    if (!eglMakeCurrent(m_egl_dsp, egl_surface, egl_surface, m_egl_context)) {
        LOGE(TAG, "EGL make current fail");
    }
}

(5)渲染

gl_render.cpp

void GLRender::Render() {
    if (RENDERING == m_state) {
        pImageRender->DoDraw();//画画画....
        m_egl_surface->SwapBuffers();
    }
}

egl_surface.cpp

void EglSurface::SwapBuffers() {
    m_core->SwapBuffer(m_surface);
}

egl_core.cpp

void EglCore::SwapBuffer(EGLSurface egl_surface) {
    //调用EGL Native API
    eglSwapBuffers(m_egl_dsp, egl_surface);
}

后面的停止与销毁就交给读者自行研究了。

代码

EGLDemoActivity.java

EGL Native