eglGetDisplay

eglGetDisplay is an EGL API function used to obtain an EGLDisplay handle for a given native display. The EGLDisplay object is an opaque handle that is used in subsequent EGL calls to manage rendering contexts, surfaces, and configurations.

Prototype and parameters: EGLDisplay eglGetDisplay(EGLNativeDisplayType display_id); The display_id argument is a platform-dependent native display handle (for example, a X11 Display*, a Wayland wl_display*, or another platform’s display handle). Some platforms also define EGL_DEFAULT_DISPLAY to request the default display. The exact type of EGLNativeDisplayType varies by implementation.

Return value and behavior: The function returns a valid EGLDisplay on success, or EGL_NO_DISPLAY if the requested display cannot be provided. Importantly, eglGetDisplay does not initialize EGL itself; it merely resolves a display object for the given native display. After obtaining a display, you must call eglInitialize to initialize EGL for that display and retrieve the major and minor version numbers.

Usage pattern: Typical usage is to call eglGetDisplay, then eglInitialize(display, &major, &minor). If initialization succeeds, the display handle is used with subsequent EGL calls such as eglChooseConfig, eglCreateContext, and eglCreateWindowSurface. If eglGetDisplay returns EGL_NO_DISPLAY, or eglInitialize fails (EGL_FALSE), you should query the error with eglGetError.

Portability and extensions: Behavior is platform-dependent, and not all native displays may be supported. Some environments provide alternative ways to obtain a display (for example, via eglGetPlatformDisplayEXT or eglGetPlatformDisplay in EGL 1.5).