Simple example of a wayland client with xdg-shell and EGL

This article provides a C code example demonstrating how to create a Wayland client that uses the xdg-shell protocol and EGL for OpenGL rendering. The code includes setup for the Wayland display, registry, compositor, and xdg-shell components, along with EGL surface and context initialization. It also implements listeners for handling window configuration, resizing, and close events.

Last active May 23, 2026 23:52 - - Save lmarz/1059f7c4101a15e2a04d6991d7b7b3d1 to your computer and use it in GitHub Desktop. Simple example of a wayland client with xdg-shell and EGL This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters. Learn more about bidirectional Unicode characters https://github.co/hiddenchars | / Compile with: | | | wayland-scanner private-code /usr/share/wayland-protocols/stable/xdg-shell/xdg-shell.xml xdg-shell.c | | | wayland-scanner client-header /usr/share/wayland-protocols/stable/xdg-shell/xdg-shell.xml xdg-shell.h | | | gcc -c xdg-shell.c | | | gcc -c egl-on-wayland-xdg.c | | | gcc -o egl-on-wayland-xdg xdg-shell.o egl-on-wayland-xdg.o -lwayland-egl -lwayland-client -lEGL -lGL | | | / | | | include <stdio.h | | | include <stdlib.h | | | include <string.h | | | include <wayland-egl.h | | | include <EGL/egl.h | | | include <GL/gl.h | | | include "xdg-shell.h" | | | struct client state { | | | struct wl display display; | | | struct wl registry registry; | | | struct wl compositor compositor; | | | struct xdg wm base xdg wm base; | | | struct wl surface surface; | | | struct xdg surface xdg surface; | | | struct xdg toplevel xdg toplevel; | | | struct wl egl window egl window; | | | EGLDisplay egl display; | | | EGLConfig egl config; | | | EGLContext egl context; | | | EGLSurface egl surface; | | | int32 t width; | | | int32 t height; | | | uint8 t running; | | | }; | | | / / | | | / Registry / | | | / / | | | static void global registry void data, struct wl registry wl registry, | | | uint32 t name, const char interface, uint32 t version { | | | struct client state state = data; | | | if strcmp interface, wl compositor interface.name { | | | state- compositor = wl registry bind wl registry, name, | | | &wl compositor interface, version ; | | | } else if strcmp interface, xdg wm base interface.name { | | | state- xdg wm base = wl registry bind wl registry, name, | | | &xdg wm base interface, version ; | | | } | | | } | | | static void global remove void data, struct wl registry wl registry, | | | uint32 t name { | | | void data; | | | void wl registry; | | | void name; | | | } | | | static const struct wl registry listener registry listener = { | | | global registry, | | | global remove | | | }; | | | / / | | | / XDG Window Manager / | | | / / | | | static void wm ping void data, struct xdg wm base xdg wm base, | | | uint32 t serial { | | | void data; | | | xdg wm base pong xdg wm base, serial ; | | | } | | | static const struct xdg wm base listener wm base listener = { | | | wm ping | | | }; | | | / / | | | / XDG Surface / | | | / / | | | static void surface configure void data, struct xdg surface xdg surface, | | | uint32 t serial { | | | void data; | | | xdg surface ack configure xdg surface, serial ; | | | } | | | static const struct xdg surface listener surface listener = { | | | surface configure | | | }; | | | / / | | | / XDG Toplevel / | | | / / | | | static void toplevel configure void data, struct xdg toplevel xdg toplevel, | | | int32 t width, int32 t height, struct wl array states { | | | struct client state state = data; | | | void xdg toplevel; | | | void states; | | | if width && height return; | | | if state- width = width || state- height = height { | | | state- width = width; | | | state- height = height; | | | wl egl window resize state- egl window, width, height, 0, 0 ; | | | wl surface commit state- surface ; | | | } | | | } | | | static void toplevel close void data, struct xdg toplevel xdg toplevel { | | | void xdg toplevel; | | | struct client state state = data; | | | state- running = 0; | | | } | | | static const struct xdg toplevel listener toplevel listener = { | | | toplevel configure, | | | toplevel close | | | }; | | | / / | | | / / | | | / / | | | static void wayland connect struct client state state { | | | state- display = wl display connect NULL ; | | | if state- display { | | | fprintf stderr, "Couldn't connect to wayland display\n" ; | | | exit EXIT FAILURE ; | | | } | | | state- registry = wl display get registry state- display ; | | | wl registry add listener state- registry, ®istry listener, state ; | | | wl display roundtrip state- display ; | | | if state- compositor || state- xdg wm base { | | | fprintf stderr, "Couldn't find compositor or xdg shell\n" ; | | | exit EXIT FAILURE ; | | | } | | | xdg wm base add listener state- xdg wm base, &wm base listener, NULL ; | | | state- surface = wl compositor create surface state- compositor ; | | | state- xdg surface = xdg wm base get xdg surface state- xdg wm base, | | | state- surface ; | | | xdg surface add listener state- xdg surface, &surface listener, NULL ; | | | state- xdg toplevel = xdg surface get toplevel state- xdg surface ; | | | xdg toplevel set title state- xdg toplevel, "Hello World" ; | | | xdg toplevel add listener state- xdg toplevel, &toplevel listener, state ; | | | wl surface commit state- surface ; | | | } | | | static void egl init struct client state state { | | | EGLint major; | | | EGLint minor; | | | EGLint num configs; | | | EGLint attribs = { | | | EGL RENDERABLE TYPE, EGL OPENGL BIT, | | | EGL NONE | | | }; | | | state- egl window = wl egl window create state- surface, state- width, | | | state- height ; | | | state- egl display = eglGetDisplay EGLNativeDisplayType state- display ; | | | if state- display == EGL NO DISPLAY { | | | fprintf stderr, "Couldn't get EGL display\n" ; | | | exit EXIT FAILURE ; | | | } | | | if eglInitialize state- egl display, &major, &minor = EGL TRUE { | | | fprintf stderr, "Couldnt initialize EGL\n" ; | | | exit EXIT FAILURE ; | | | } | | | if eglChooseConfig state- egl display, attribs, &state- egl config, 1, | | | &num configs = EGL TRUE { | | | fprintf stderr, "CouldnÄt find matching EGL config\n" ; | | | exit EXIT FAILURE ; | | | } | | | state- egl surface = eglCreateWindowSurface state- egl display, | | | state- egl config, | | | EGLNativeWindowType state- egl window, NULL ; | | | if state- egl surface == EGL NO SURFACE { | | | fprintf stderr, "Couldn't create EGL surface\n" ; | | | exit EXIT FAILURE ; | | | } | | | state- egl context = eglCreateContext state- egl display, state- egl config, | | | EGL NO CONTEXT, NULL ; | | | if state- egl context == EGL NO CONTEXT { | | | fprintf stderr, "Couldn't create EGL context\n" ; | | | exit EXIT FAILURE ; | | | } | | | if eglMakeCurrent state- egl display, state- egl surface, | | | state- egl surface, state- egl context { | | | fprintf stderr, "Couldn't make EGL context current\n" ; | | | exit EXIT FAILURE ; | | | } | | | } | | | static void draw struct client state state { | | | glClearColor 0.0/255, 79.0/255, 158.0/255, 1.0 ; | | | glClear GL COLOR BUFFER BIT ; | | | eglSwapBuffers state- egl display, state- egl surface ; | | | } | | | int main int argc, char const argv { | | | struct client state state; | | | state.width = 800; | | | state.height = 600; | | | state.running = 1; | | | wayland connect &state ; | | | egl init &state ; | | | while state.running { | | | wl display dispatch pending state.display ; | | | draw &state ; | | | } | | | eglDestroySurface state.egl display, state.egl surface ; | | | eglDestroyContext state.egl display, state.egl context ; | | | wl egl window destroy state.egl window ; | | | xdg toplevel destroy state.xdg toplevel ; | | | xdg surface destroy state.xdg surface ; | | | wl surface destroy state.surface ; | | | wl display disconnect state.display ; | | | return 0; | | | } | I just want to add my 2 cents: On a current Archlinux System with Gnome mutter compositor , I see two problems: Couldn't create EGL context This is solved by adding eglBindAPI EGL OPENGL API ; before creating the EGL context, e.g. in line 184 https://gist.github.com/lmarz/1059f7c4101a15e2a04d6991d7b7b3d1 file-egl-on-wayland-xdg-c-L184 . listener function for opcode 2/3 of xdg toplevel is NULL Add the appropriate listener functions to 126 https://gist.github.com/lmarz/1059f7c4101a15e2a04d6991d7b7b3d1 file-egl-on-wayland-xdg-c-L126 : static void toplevel configure bounds void data, struct xdg toplevel xdg toplevel, int32 t width, int32 t height { } static void toplevel wm capabilities void data, struct xdg toplevel xdg toplevel, struct wl array capabilities { } static const struct xdg toplevel listener toplevel listener = { toplevel configure, toplevel close, toplevel configure bounds, toplevel wm capabilities }; For me it was enough to simply implement them with an empty body.