Android OpenGL ES - EGL C++實現

PS
本篇繼續上一篇的內容，咱們來對Native EGL環境實現的各個步驟進行詳細解析

EGL Native層的實現

上一篇文章Android OpenGL ES - EGL源碼解析以及C++實現

咱們仍是先來回顧一下流程圖

以及代碼

//(1) 將線程附加到虛擬機，並獲取env
     if (that->m_jvm_for_thread->AttachCurrentThread(&env, NULL) != JNI_OK) {
            LOGE(that->TAG, "線程初始化異常");
            return; 
     }
     // (2) 初始化 EGL 
    if (!that->InitEGL()) {
         //解除線程和jvm關聯
         that->m_jvm_for_thread->DetachCurrentThread();
         return; 
     }
     
     //進入循環
    while (true) {
            //根據OpenGL渲染狀態進入不一樣的處理
            switch (that->m_state) {
                //刷新Surface，從外面設置Surface後m_state置爲該狀態，說明已經從外部(java層)得到Surface的對象了
                case FRESH_SURFACE:
                     LOGI(that->TAG, "Loop Render FRESH_SURFACE")
                     // (3) 初始化Window
                     that->InitDspWindow(env);
                     // (4) 建立EglSurface
                     that->CreateSurface();
                     // m_state置爲RENDERING狀態進入渲染
                     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) 解除線程和jvm關聯
                     that->ReleaseRender();
                     that->m_jvm_for_thread->DetachCurrentThread();
                     return; 
                case SURFACE_DESTROY:
                    LOGI(that->TAG, "Loop Render SURFACE_DESTROY")
                    //(7) 釋放資源
                    that->DestroySurface();
                    that->m_state = NO_SURFACE;
                    break; 
                case NO_SURFACE:
                default:
                    break;
     }
    usleep(20000);
 }
}

首先第(1)步將線程附加到虛擬機，並獲取env,這一步簡單明瞭，咱們從第(2)步開始

EGL封裝準備

咱們在上一篇就知道了EGL的一些基礎知識，EGLDiaplay,EGLConfig,EGLSurface,EGLContext，咱們須要把這些基礎類進行封裝，那麼如何進行封裝呢，咱們先看一下對於咱們上篇文章中自定義的GLRender類須要什麼
gl_render.h

//Surface引用，必需要使用引用，不然沒法在線程中操做
jobject m_surface_ref = NULL;
//本地屏幕
ANativeWindow *m_native_window = NULL;
//EGL顯示錶面 注意這裏是咱們自定義的EglSurface包裝類而不是系統提供的EGLSurface哦
EglSurface *m_egl_surface = NULL;

對於gl_render來講輸入的是外部的Surface對象，咱們這裏的是jobject m_surface_ref,那麼輸出須要的是ANativeWindow,EglSurface

關於 ANativeWindow能夠查看官方文檔 ANativeWindow

那麼EglSurface呢，

egl_surface.h

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

能夠看到咱們上面的定義的思想也是V(View)和C(Controller)進行了分離。

egl_core.h

class EglCore {
private:
    const char *TAG = "EglCore";
     //EGL顯示窗口
     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;
}

有了上面的準備工做後，咱們就跟着流程圖的步驟來一步步走

(2)初始化EGL

gl_render.cpp

bool GLRender::InitEGL() {
    //建立EglSurface對象
    m_egl_surface = new EglSurface();
    //調用EglSurface的init方法
    return m_egl_surface->Init();
}

egl_surface.cpp

PS
咱們上面也說了EGL的初始化主要是對EGLDisplay EGLConfig EGLContext的操做，因此如今是對EGLCore的操做

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

bool EglSurface::Init() {
    //調用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;
     }
     //獲取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)
     //獲取EGLConfig   
     m_egl_config = GetEGLConfig();
     const EGLint attr[] = {EGL_CONTEXT_CLIENT_VERSION, 2, EGL_NONE};
     //建立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;

    //但願的最小配置，
    static const EGLint CONFIG_ATTRIBS[] = {
            EGL_BUFFER_SIZE, EGL_DONT_CARE,
            EGL_RED_SIZE, 8,//R 位數
            EGL_GREEN_SIZE, 8,//G 位數
            EGL_BLUE_SIZE, 8,//B 位數
            EGL_ALPHA_SIZE, 8,//A 位數
            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 結束標誌
    };
    //根據你所設定的最小配置系統會選擇一個知足你最低要求的配置，這個真正的配置每每要比你指望的屬性更多
    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）建立Window

gl_render.cpp

void GLRender::InitDspWindow(JNIEnv *env) {
    //傳進來的Surface對象的引用
    if (m_surface_ref != NULL) {
        // 初始化窗口
        m_native_window = ANativeWindow_fromSurface(env, m_surface_ref);

        // 繪製區域的寬高
        m_window_width = ANativeWindow_getWidth(m_native_window);
        m_window_height = ANativeWindow_getHeight(m_native_window);

        //設置寬高限制緩衝區中的像素數量
        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)建立EglSurface並綁定到線程

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 傳入上一步建立的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) {
    //調用EGL Native API建立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) {
    //調用EGL Native API 綁定渲染環境到當前線程
    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();//畫畫畫....
        m_egl_surface->SwapBuffers();
    }
}

egl_surface.cpp

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

egl_core.cpp

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

後面的中止與銷燬就交給讀者自行研究了。

代碼

EGLDemoActivity.java

EGL Native