EGL 平台无关配置封装

	/**
	 * Creates an EGL rendering context and all associated elements
	 */
	void (*CreateEGL)              (EGLNativeWindowType window, EGLDisplay* outDisplay, EGLContext* outContext, EGLSurface* outSurface, EGLConfig*  outConfig);


	/**
	 * Destroy EGL context and all associated elements
	 */
	void (*DestroyEGL)             (EGLDisplay* display, EGLContext* context, EGLSurface* surface);


	/**
	 * When native window resized, we need reset surface
	 * the surface will destroyed and create new one and make current
	 */
	void (*ResetSurface)           (EGLNativeWindowType window, EGLDisplay display, EGLContext context, EGLConfig config, EGLSurface* surface);

out前缀的参数是出参数。ResetSurface 在系统OnResize的时候调用。因为在OnResize的时候，window的with和height会改变，这个只会影响surface，所以只需摧毁surface重建新的surface，然后重新调用eglMakeCurrent即可。ResetSurface需要的config，就是CreateEGL最后返回的config参数。

/**
 * Creates an EGL rendering context and all associated elements
 */
void CreateEGL(EGLNativeWindowType window, EGLDisplay* outDisplay, EGLContext* outContext, EGLSurface* outSurface, EGLConfig*  outConfig)
{

	*outDisplay = eglGetDisplay(EGL_DEFAULT_DISPLAY);

	if (*outDisplay == EGL_NO_DISPLAY)
	{
		ALog_A(0, "CreateEGL failed EGL unable to eglGetDisplay");
	}

	if (!eglInitialize(*outDisplay, NULL/*major*/, NULL/*minor*/))
	{
		ALog_A(0, "CreateEGL failed EGL unable to eglInitialize");
	}

	EGLint numConfigs;

	// Here specify the attributes of the desired configuration.
	// Below, we select an EGLConfig with at least 8 bits per color
	// component compatible with on-screen windows
	const EGLint configAttribs[] =
	{
		   EGL_DEPTH_SIZE,      16,
		   EGL_RED_SIZE,        8,   //   5,
		   EGL_GREEN_SIZE,      8,   //   6,
		   EGL_BLUE_SIZE,       8,   //   5,
		   EGL_ALPHA_SIZE,      8,   //   0,
		   EGL_STENCIL_SIZE,    8,
		   EGL_SURFACE_TYPE,    EGL_WINDOW_BIT,
		   EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
		   EGL_NONE
	};

	/* Here, the application chooses the configuration it desires. In this
	 * sample, we have a very simplified selection process, where we pick
	 * the first EGLConfig that matches our criteria
	 */
	eglChooseConfig(*outDisplay, configAttribs, outConfig, 1, &numConfigs);

	if (numConfigs < 1)
	{
		ALog_A(0, "CreateEGL failed no config match eglChooseConfig");
	}

	const EGLint surfaceAttrs[] =
	{
		EGL_RENDER_BUFFER,
		EGL_BACK_BUFFER,
		EGL_NONE
	};

	*outSurface = eglCreateWindowSurface(*outDisplay, *outConfig, window, surfaceAttrs);
	if (*outSurface == EGL_NO_SURFACE)
	{
		ALog_A(0, "CreateEGL failed EGL unable to eglCreateWindowSurface");
	}

	const EGLint contextAttribs[] =
	{
		EGL_CONTEXT_CLIENT_VERSION, 2,
		EGL_NONE
	};

	*outContext = eglCreateContext(*outDisplay, *outConfig, EGL_NO_CONTEXT, contextAttribs);
	if (*outContext == EGL_NO_CONTEXT)
	{
		ALog_A(0, "CreateEGL failed EGL unable to eglCreateContext");
	}

	if (!eglMakeCurrent(*outDisplay, *outSurface, *outSurface, *outContext))
	{
		ALog_A(0, "CreateEGL failed EGL unable to eglMakeCurrent");
	}

//	eglSwapInterval(*outDisplay, 0);
}


/**
 * Destroy EGL context and all associated elements
 */
void DestroyEGL(EGLDisplay* display, EGLContext* context, EGLSurface* surface)
{
    if (*display != EGL_NO_DISPLAY)
    {
        eglMakeCurrent(*display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);

        if (*context != EGL_NO_CONTEXT)
        {
            eglDestroyContext(*display, *context);
        }

        if (*surface != EGL_NO_SURFACE)
        {
            eglDestroySurface(*display, *surface);
        }

        eglTerminate(*display);
    }

    *display = EGL_NO_DISPLAY;
    *context = EGL_NO_CONTEXT;
    *surface = EGL_NO_SURFACE;
}

static void ResetSurface(EGLNativeWindowType window, EGLDisplay display, EGLContext context, EGLConfig config, EGLSurface* surface)
{
    if (*surface != EGL_NO_SURFACE)
    {
        eglDestroySurface(display, *surface);
    }

	const EGLint surfaceAttrs[] =
	{
		EGL_RENDER_BUFFER,
		EGL_BACK_BUFFER,
		EGL_NONE
	};

	*surface = eglCreateWindowSurface(display, config, window, surfaceAttrs);

	if (!eglMakeCurrent(display, *surface, *surface, context))
	{
		ALog_A(0, "ResetSurface failed EGL unable to eglMakeCurrent");
	}
}

代码与平台无关，只需要EGL的头文件。