wayland-egl: Make wl_egl_window a versioned struct

We need wl_egl_window to be a versioned struct in order to keep track of
ABI changes.

This change makes the first member of wl_egl_window the version number.

An heuristic in the wayland driver is added so that we don't break
backwards compatibility:

 - If the first field (version) is an actual pointer, it is an old
   implementation of wl_egl_window, and version points to the wl_surface
   proxy.

 - Else, the first field is the version number, and we have
   wl_egl_window::surface pointing to the wl_surface proxy.

Signed-off-by: Miguel A. Vico <mvicomoya@nvidia.com>
Reviewed-by: James Jones <jajones@nvidia.com>
Acked-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

src/egl/drivers/dri2/platform_wayland.c

@@ -43,6 +43,7 @@
 #include "egl_dri2_fallbacks.h"
 #include "loader.h"
 #include "util/u_vector.h"
+#include "eglglobals.h"
 
 #include <wayland-client.h>
 #include "wayland-drm-client-protocol.h"
@@ -111,6 +112,19 @@ destroy_window_callback(void *data)
    dri2_surf->wl_win = NULL;
 }
 
+static struct wl_surface *
+get_wl_surface_proxy(struct wl_egl_window *window)
+{
+    /* Version 3 of wl_egl_window introduced a version field at the same
+     * location where a pointer to wl_surface was stored. Thus, if
+     * window->version is dereferencable, we've been given an older version of
+     * wl_egl_window, and window->version points to wl_surface */
+   if (_eglPointerIsDereferencable((void *)(window->version))) {
+      return wl_proxy_create_wrapper((void *)(window->version));
+   }
+   return wl_proxy_create_wrapper(window->surface);
+}
+
 /**
  * Called via eglCreateWindowSurface(), drv->API.CreateWindowSurface().
  */
@@ -182,7 +196,7 @@ dri2_wl_create_window_surface(_EGLDriver *drv, _EGLDisplay *disp,
    wl_proxy_set_queue((struct wl_proxy *)dri2_surf->wl_dpy_wrapper,
                       dri2_surf->wl_queue);
 
-   dri2_surf->wl_surface_wrapper = wl_proxy_create_wrapper(window->surface);
+   dri2_surf->wl_surface_wrapper = get_wl_surface_proxy(window);
    if (!dri2_surf->wl_surface_wrapper) {
       _eglError(EGL_BAD_ALLOC, "dri2_create_surface");
       goto cleanup_drm;

src/egl/wayland/wayland-egl/wayland-egl-priv.h

@@ -41,8 +41,10 @@
 extern "C" {
 #endif
 
+#define WL_EGL_WINDOW_VERSION 3
+
 struct wl_egl_window {
-	struct wl_surface *surface;
+	const intptr_t version;
 
 	int width;
 	int height;
@@ -55,6 +57,8 @@ struct wl_egl_window {
 	void *private;
 	void (*resize_callback)(struct wl_egl_window *, void *);
 	void (*destroy_window_callback)(void *);
+
+	struct wl_surface *surface;
 };
 
 #ifdef  __cplusplus

src/egl/wayland/wayland-egl/wayland-egl.c

@@ -28,6 +28,7 @@
  */
 
 #include <stdlib.h>
+#include <string.h>
 
 #include <wayland-client.h>
 #include "wayland-egl.h"
@@ -54,6 +55,7 @@ WL_EGL_EXPORT struct wl_egl_window *
 wl_egl_window_create(struct wl_surface *surface,
 		     int width, int height)
 {
+	struct wl_egl_window _INIT_ = { .version = WL_EGL_WINDOW_VERSION };
 	struct wl_egl_window *egl_window;
 
 	if (width <= 0 || height <= 0)
@@ -63,6 +65,8 @@ wl_egl_window_create(struct wl_surface *surface,
 	if (!egl_window)
 		return NULL;
 
+	memcpy(egl_window, &_INIT_, sizeof *egl_window);
+
 	egl_window->surface = surface;
 	egl_window->private = NULL;
 	egl_window->resize_callback = NULL;