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 <[email protected]>
Reviewed-by: James Jones <[email protected]>
Acked-by: Daniel Stone <[email protected]>
Reviewed-by: Emil Velikov <[email protected]>

2 files changed, 9 insertions, 1 deletions

diff --git a/src/egl/wayland/wayland-egl/wayland-egl-priv.h b/src/egl/wayland/wayland-egl/wayland-egl-priv.h
index 92c31d94543..3b59908cc16 100644
--- a/src/egl/wayland/wayland-egl/wayland-egl-priv.h
+++ b/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
diff --git a/src/egl/wayland/wayland-egl/wayland-egl.c b/src/egl/wayland/wayland-egl/wayland-egl.c
index 4a4701a2de7..f16324c9f61 100644
--- a/src/egl/wayland/wayland-egl/wayland-egl.c
+++ b/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;