---

前言

`本文主要介绍如何在linux 下，基于xdg_wm_base 接口的 wayland client 中 使用 egl + opengles 渲染一个最基本的三角形
软硬件环境：
硬件：PC
软件：
ubuntu22.04
EGL1.4
openGL ES3.1
weston9.0

---

一、ubuntu 下相关环境准备

1. 获取 xdg_wm_base 依赖的相关文件

之前的文章 weston 源码下载及编译 介绍了如何在ubuntu 22.04 下面编译 weston9.0 ，在编译结束后，在build 目录下会生成 xdg-shell-protocol.c 和 xdg-shell-client-protocol.h 这两个文件，如下图所示

xdg-shell-protocol.c 和 xdg-shell-client-protocol.h 这两个文件就是使用 xdg_wm_base 时所依赖的，这里就直接从weston9.0的目录下获取了，当然也可以使用wayland 相关的命令(wayland-scanner)去操作对应的.xml 文件来生成它们。

（wayland-scanner）是一个用于生成Wayland协议代码的工具。它是Wayland项目的一部分，用于根据XML描述文件生成C语言代码，以便在应用程序中使用Wayland协议。
Wayland-Scanner工具的用途是将Wayland协议的XML描述文件转换为可供应用程序使用的C语言代码。这些代码包括客户端和服务器端的接口定义、消息处理函数、数据结构等。通过使用Wayland-Scanner，开发人员可以根据自定义的Wayland协议描述文件生成所需的代码，从而实现与Wayland服务器的通信

2. 查看 ubuntu 上安装的opengles 版本

使用 glxinfo | grep “OpenGL ES” 可以查看 ubuntu 上所安装的opengles 的版本，如下图所示，代表当前 ubuntu （ubuntu22.04）上安装的是opengles版本是 opengles3.1

3. 查看 weston 所支持的 窗口shell 接口种类

直接执行 weston-info（后面会被wayland-info 命令取代） 命令，如下图所示，可以看到，当前ubuntu（ubuntu22.04）上所支持的窗口 shell 接口种类，其中就有 xdg_wm_base, zxdg_shell_v6 等，但是没有 wl_shell , 所以从这可以看出，wl_shell 确实已经在ubuntu22.04 上废弃使用了。

二、xdg_wm_base 介绍

• xdg_wm_base是由XDG组织定义的Wayland协议接口之一，它提供了一种标准化的方法，使得窗口管理器和应用程序能够进行互动；
• xdg_wm_base定义了与窗口管理器交互的基本功能，如创建新窗口、设置窗口标题、最大化和最小化窗口等；
• 它鼓励窗口管理器使用更加灵活和自由的方式来处理窗口管理任务；
• xdg_wm_base和 wl_shell 都是Wayland协议的一部分，用于定义窗口管理器（Window Manager）与应用程序之间的通信接口。它们之间的区别在于设计理念和功能，xdg_wm_base提供了更加灵活和标准化的窗口管理器接口，窗口管理器可以根据需要实现更多的功能；

三、egl_wayland_demo

1.egl_wayland_demo2_0.c

使用 opengles2.x 接口的 egl_wayland_demo2_0.c 代码如下

#include <wayland-client.h>
#include <wayland-server.h>
#include <wayland-egl.h>
#include <EGL/egl.h>
#include <GLES2/gl2.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "xdg-shell-client-protocol.h"

#define WIDTH 640
#define HEIGHT 480

struct wl_display *display = NULL;
struct wl_compositor *compositor = NULL;
struct xdg_wm_base *wm_base = NULL;
struct wl_registry *registry = NULL;

struct window {
   
	struct wl_surface *surface;
    struct xdg_surface *xdg_surface;
	struct xdg_toplevel *xdg_toplevel;
	struct wl_egl_window *egl_window;
};

// Index to bind the attributes to vertex shaders
const unsigned int VertexArray = 0;

static void
xdg_wm_base_ping(void *data, struct xdg_wm_base *shell, uint32_t serial)
{
   
	xdg_wm_base_pong(shell, serial);
}

static const struct xdg_wm_base_listener wm_base_listener = {
   
	xdg_wm_base_ping,
};

/*for registry listener*/
static void registry_add_object(void *data, struct wl_registry *registry, uint32_t name, const char *interface, uint32_t version) 
{
   
    if (!strcmp(interface, "wl_compositor")) {
   
        compositor = wl_registry_bind(registry, name, &wl_compositor_interface, 1);
    } else if (strcmp(interface, "xdg_wm_base") == 0) {
   
        wm_base = wl_registry_bind(registry, name,
            &xdg_wm_base_interface, 1);
        xdg_wm_base_add_listener(wm_base, &wm_base_listener, NULL);
    }
}

void registry_remove_object(void *data, struct wl_registry *registry, uint32_t name) 
{
   

}

static struct wl_registry_listener registry_listener = {
   registry_add_object, registry_remove_object};

static void
handle_surface_configure(void *data, struct xdg_surface *surface,
			 uint32_t serial)
{
   
	//struct window *window = data;

	xdg_surface_ack_configure(surface, serial);

	//window->wait_for_configure = false;
}

static const struct xdg_surface_listener xdg_surface_listener = {
   
	handle_surface_configure
};

static void
handle_toplevel_configure(void *data, struct xdg_toplevel *toplevel,
			  int32_t width, int32_t height,
			  struct wl_array *states)
{
   
}

static void
handle_toplevel_close(void *data, struct xdg_toplevel *xdg_toplevel)
{
   
}

static const struct xdg_toplevel_listener xdg_toplevel_listener = {
   
	handle_toplevel_configure,
	handle_toplevel_close,
};

bool initWaylandConnection()
{
   	
	if ((display = wl_display_connect(NULL)) == NULL)
	{
   
		printf("Failed to connect to Wayland display!\n");
		return false;
	}

	if ((registry = wl_display_get_registry(display)) == NULL)
	{
   
		printf("Faield to get Wayland registry!\n");
		return false;
	}

	wl_registry_add_listener(registry, &registry_listener, NULL);
	wl_display_dispatch(display);

	if (!compositor)
	{
   
		printf("Could not bind Wayland protocols!\n");
		return false;
	}

	return true;
}

bool initializeWindow(struct window *window)
{
   
	initWaylandConnection();
	window->surface = wl_compositor_create_surface (compositor);
	window->xdg_surface = xdg_wm_base_get_xdg_surface(wm_base, window->surface);
    if (window->xdg_surface == NULL)
    {
   
        printf("Failed to get Wayland xdg surface\n");
        return false;
    } else {
   
        xdg_surface_add_listener(window->xdg_surface, &xdg_surface_listener, window);
        window->xdg_toplevel =
            xdg_surface_get_toplevel(window->xdg_surface);
        xdg_toplevel_add_listener(window->xdg_toplevel,
            &xdg_toplevel_listener, window);
        xdg_toplevel_set_title(window->xdg_toplevel, "egl_wayland_demo");
    }
	return true;
}

void releaseWaylandConnection(struct window *window)
{
   
    if(window->xdg_toplevel)
        xdg_toplevel_destroy(window->xdg_toplevel);
    if(window->xdg_surface)
	    xdg_surface_destroy(window->xdg_surface);
	wl_surface_destroy(window->surface);
	xdg_wm_base_destroy(wm_base);
	wl_compositor_destroy(compositor);
	wl_registry_destroy(registry);
	wl_display_disconnect(display);
}

bool createEGLSurface(EGLDisplay eglDisplay, EGLConfig eglConfig, EGLSurface *eglSurface, struct window *window)
{
   

	window->egl_window = wl_egl_window_create(window->surface, WIDTH, HEIGHT);
	if (window->egl_window == EGL_NO_SURFACE) {
    
		printf("Can't create egl window\n"); 
		return false;
	} else {
   
		printf("Created wl egl window\n");
	}

	*eglSurface = eglCreateWindowSurface(eglDisplay, eglConfig, window->egl_window, NULL);
	
	return true;
}

bool opengles_init(GLuint *shaderProgram)
{
   
	GLuint fragmentShader = 0;
	GLuint vertexShader = 0;
	char msg[1000];
	GLsizei len;


	const char* const fragmentShaderSource = 
		"precision mediump float;\n"
		"void main()\n"
		"{\n"
		"   gl_FragColor = vec4 (1.0,0.0,0.0,1.0);\n"
		"}\n";


	// Create a fragment shader object
	fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);

	// Load the source code into it
	glShaderSource(fragmentShader, 1, (const char**)&fragmentShaderSource, NULL);
	
	// Compile the source code
	glCompileShader(fragmentShader);

	// Check that the shader compiled
	GLint isShaderCompiled;
	glGetShaderiv(fragmentShader, GL_COMPILE_STATUS, &isShaderCompiled);
	if (!isShaderCompiled)
	{
   
		// If an error happened, first retrieve the length of the log message

		glGetShaderInfoLog(fragmentShader, sizeof msg, &len, msg);
		//glGetShaderiv(fragmentShader, GL_INFO_LOG_LENGTH, &infoLogLength);

		// Allocate enough space for the message and retrieve it
		//std::vector<char> infoLog;
		//infoLog.resize(infoLogLength);
		//glGetShaderInfoLog(fragmentShader, infoLogLength, &charactersWritten, infoLog.data());
		fprintf(stderr, "Error: compiling %s: %.*s\n", "fragment", len, msg);
		return false;
	}

	// Vertex shader code
	const char* const vertexShaderSource =		
		"attribute vec4 vPosition; \n"
		"void main()\n"
		"{\n"
		"   gl_Position = vPosition;\n"
		"}\n";

	// Create a vertex shader object
	vertexShader = glCreateShader(GL_VERTEX_SHADER);

	// Load the source code into the shader
	glShaderSource(vertexShader, 1, (const char**)&vertexShaderSource, NULL);

	// Compile the shader
	glCompileShader(vertexShader);

	// Check the shader has compiled
	glGetShaderiv(vertexShader, GL_COMPILE_STATUS, &isShaderCompiled);
	if (!isShaderCompiled)
	{
   
		// If an error happened, first retrieve the length of the log message
		//int infoLogLength, charactersWritten;
		//glGetShaderiv(vertexShader, GL_INFO_LOG_LENGTH, &infoLogLength);

		glGetShaderInfoLog(vertexShader, sizeof msg, &len, msg);

		// Allocate enough space for the message and retrieve it
		//std::vector<char> infoLog;
		//infoLog.resize(infoLogLength);
		//glGetShaderInfoLog(vertexShader, infoLogLength, &charactersWritten, infoLog.data());
		fprintf(stderr, "Error: compiling %s: %.*s\n", "vertex", len, msg);
		return false;
	}

	// Create the shader program
	*shaderProgram = glCreateProgram();

	// Attach the fragment and vertex shaders to it
	glAttachShader(*shaderProgram, fragmentShader);
	glAttachShader(*shaderProgram, vertexShader);

	// Bind the vertex attribute "myVertex" to location VertexArray (0)
	glBindAttribLocation(*shaderProgram, VertexArray, "vPosition");

	// Link the program
	glLinkProgram(*shaderProgram);

	// After linking the program, shaders are no longer necessary
	glDeleteShader(vertexShader);
	glDeleteShader(fragmentShader);

	// Check if linking succeeded in the same way we checked for compilation success
	GLint isLinked;
	glGetProgramiv(*shaderProgram, GL_LINK_STATUS, &isLinked);

	if (!isLinked)
	{
   
		// If an error happened, first retrieve the length of the log message
		//nt infoLogLength, charactersWritten;
		//glGetProgramiv(*shaderProgram, GL_INFO_LOG_LENGTH, &infoLogLength);

		// Allocate enough space for the message and retrieve it
		//std::vector<char> infoLog;
		//infoLog.resize(infoLogLength);
		//glGetShaderInfoLog(shaderProgram, infoLogLength, &charactersWritten, infoLog.data());
		glGetProgramInfoLog(*shaderProgram, sizeof msg, &len, msg);
		fprintf(stderr, "Error: compiling %s: %.*s\n", "linkprogram", len, msg);

		return false;
	}

	//	Use the Program
	glUseProgram(*shaderProgram);

	return true;
}
bool renderScene(EGLDisplay eglDisplay, EGLSurface eglSurface)
{
   
	GLfloat vVertices[] = {
   0.0f,0.5f,0.0f,			//vertex pointer
		-0.5f,-0.5f,0.0f,
		0.5f,-0.5f,0.0f};

	glViewport(0, 0, WIDTH, HEIGHT);			//set the view port
	glClearColor(0.00f, 0.70f, 0.67f, 1.0f);		//set rgba value for backgroud 
	glClear(GL_COLOR_BUFFER_BIT);


	glEnableVertexAttribArray(VertexArray);
	glVertexAttribPointer(VertexArray, 3, GL_FLOAT, GL_FALSE, 0, vVertices);
	glDrawArrays(GL_TRIANGLES, 0, 3);			//draw a triangle

	
	if (!eglSwapBuffers(eglDisplay, eglSurface))
	{
   
		return false;
	}

	return true;

}

bool render(GLuint shaderProgram, EGLDisplay eglDisplay, EGLSurface eglSurface)
{
   
	// Renders a triangle for 800 frames using the state setup in the previous function
	for (int i = 0; i < 800; ++i)
	{
   
		wl_display_dispatch_pending(display);
		if (!renderScene(eglDisplay, eglSurface)) {
    return false; }
	}
	return true;
}

void deInitializeGLState(GLuint shaderProgram)
{
   
	// Frees the OpenGL handles for the program
	glDeleteProgram(shaderProgram);
}

void releaseEGLState(EGLDisplay eglDisplay)
{
   
	if (eglDisplay != NULL)
	{
   
		// To release the resources in the context, first the context has to be released from its binding with the current thread.
		eglMakeCurrent(eglDisplay, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);

		// Terminate the display, and any resources associated with it (including the EGLContext)
		eglTerminate(eglDisplay);
	}
}



int main()
{
   
	/* EGL variables*/
	EGLDisplay eglDisplay;
	EGLConfig eglConfig;
	EGLSurface eglSurface;
	EGLContext context;
	struct window window;

	//wayland client init
	if(!initializeWindow(&window))
	{
   
		printf("initializeWindow failed\n");
		return -1;
	}

	//egl init	
	eglDisplay = eglGetDisplay(display);
	if (eglDisplay == EGL_NO_DISPLAY)
	{
   
		printf("Failed to get an EGLDisplay\n");
		return -1;
	}

	EGLint eglMajorVersion = 0;
	EGLint eglMinorVersion = 0;
    if (!eglInitialize(eglDisplay, &eglMajorVersion, &eglMinorVersion))
    {
   
        printf("Failed to initialize the EGLDisplay\n");
        return -1;
    } else {
   
        printf(" EGL%d.%d\n", eglMajorVersion, eglMinorVersion);
        printf(" EGL_CLIENT_APIS: %s\n", eglQueryString(eglDisplay, EGL_CLIENT_APIS));
        printf(" EGL_VENDOR: %s\n", eglQueryString(eglDisplay,  EGL_VENDOR));
        printf(" EGL_VERSION: %s\n", eglQueryString(eglDisplay,  EGL_VERSION));
        printf(" EGL_EXTENSIONS: %s\n", eglQueryString(eglDisplay,  EGL_EXTENSIONS));
    }

    int result = EGL_FALSE;
    result = eglBindAPI(EGL_OPENGL_ES_API);
    if (result != EGL_TRUE) {
    
        printf("eglBindAPI failed\n");
        return -1; 
    }
 
	const EGLint configurationAttributes[] = {
    EGL_SURFACE_TYPE, EGL_WINDOW_BIT, EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT, EGL_NONE };
	EGLint configsReturned;
	if (!eglChooseConfig(eglDisplay, configurationAttributes, &eglConfig, 1, &configsReturned) || (configsReturned != 1))
	{
   
		printf("Failed to choose a suitable config\n");
		return -1;
	}

	EGLint contextAttributes[] = {
    EGL_CONTEXT_CLIENT_VERSION, 2, EGL_NONE };
	context = eglCreateContext(eglDisplay, eglConfig, NULL, contextAttributes);

	if(!createEGLSurface(eglDisplay, eglConfig, &eglSurface, &window))
	{
   
		printf("Failed to create EGLSurface\n");
		return -1;
	}

	eglMakeCurrent(eglDisplay, eglSurface, eglSurface, context);
 
    const GLubyte* version = glGetString(GL_VERSION);
    if (version != NULL) {
   
        printf("OpenGL ES version: %s\n", version);
    } else {
   
        printf("Failed to get OpenGL ES version\n");
    }

	// opengles init
	GLuint shaderProgram = 0;
	opengles_init(&shaderProgram);

	//render
	if(!render(shaderProgram, eglDisplay, eglSurface)) {
   
		printf("=========render failed\n");
	}

	//clean up
	deInitializeGLState(shaderProgram);

	// Release the EGL State
	releaseEGLState(eglDisplay);

	// Release the Wayland connection
	releaseWaylandConnection(&window);

	return 0;
}

2.egl_wayland_demo3_0.c

使用 opengles3.x 接口的 egl_wayland_demo3_0.c 代码如下

#include <wayland-client.h>
#include <wayland-server.h>
#include <wayland-egl.h>
#include <EGL/egl.h>
#include <GLES3/gl3.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "xdg-shell-client-protocol.h"

#define WIDTH 640
#define HEIGHT 480

struct wl_display *display = NULL;
struct wl_compositor *compositor = NULL;
struct xdg_wm_base *wm_base = NULL;
struct wl_registry *registry = NULL;

struct window {
   
	struct wl_surface *surface;
    struct xdg_surface *xdg_surface;
	struct xdg_toplevel *xdg_toplevel;
	struct wl_egl_window *egl_window;
};

// Index to bind the attributes to vertex shaders
const unsigned int VertexArray = 0;

static void
xdg_wm_base_ping(void *data, struct xdg_wm_base *shell, uint32_t serial)
{
   
	xdg_wm_base_pong(shell, serial);
}

static const struct xdg_wm_base_listener wm_base_listener = {
   
	xdg_wm_base_ping,
};

/*for registry listener*/
static void registry_add_object(void *data, struct wl_registry *registry, uint32_t name, const char *interface, uint32_t