wayland: implement foreign surfaces for CoglOnscreen

This adds support for optionally providing a foreign Wayland surface to
a CoglOnscreen before allocation. Setting a foreign surface prevents
Cogl from creating a toplevel Wayland shell surface for the OnScreen.

Reviewed-by: Robert Bragg <robert@linux.intel.com>

(cherry picked from commit e447d9878f3bcfe5fe336d367238383b02879223)

cogl/cogl-onscreen-private.h

@@ -86,6 +86,10 @@ struct _CoglOnscreen
   HWND foreign_hwnd;
 #endif
 
+#ifdef COGL_HAS_EGL_PLATFORM_WAYLAND_SUPPORT
+  struct wl_surface *foreign_surface;
+#endif
+
   CoglBool swap_throttled;
 
   CoglFrameCallbackList frame_closures;

cogl/cogl-onscreen.h

@@ -187,6 +187,25 @@ cogl_wayland_onscreen_get_surface (CoglOnscreen *onscreen);
 struct wl_shell_surface *
 cogl_wayland_onscreen_get_shell_surface (CoglOnscreen *onscreen);
 
+/**
+ * cogl_wayland_onscreen_set_foreign_surface:
+ * @onscreen: An unallocated framebuffer.
+ * @surface A Wayland surface to associate with the @onscreen.
+ *
+ * Allows you to explicitly notify Cogl of an existing Wayland surface to use,
+ * which prevents Cogl from allocating a surface and shell surface for the
+ * @onscreen. An allocated surface will not be destroyed when the @onscreen is
+ * freed.
+ *
+ * This function must be called before @onscreen is allocated.
+ *
+ * Since: 1.16
+ * Stability: unstable
+ */
+void
+cogl_wayland_onscreen_set_foreign_surface (CoglOnscreen *onscreen,
+                                           struct wl_surface *surface);
+
 /**
  * cogl_wayland_onscreen_resize:
  * @onscreen: A #CoglOnscreen framebuffer

cogl/winsys/cogl-winsys-egl-wayland.c

@@ -324,8 +324,12 @@ _cogl_winsys_egl_onscreen_init (CoglOnscreen *onscreen,
   wayland_onscreen = g_slice_new0 (CoglOnscreenWayland);
   egl_onscreen->platform = wayland_onscreen;
 
-  wayland_onscreen->wayland_surface =
+  if (onscreen->foreign_surface)
-    wl_compositor_create_surface (wayland_renderer->wayland_compositor);
+    wayland_onscreen->wayland_surface = onscreen->foreign_surface;
+  else
+    wayland_onscreen->wayland_surface =
+      wl_compositor_create_surface (wayland_renderer->wayland_compositor);
+
   if (!wayland_onscreen->wayland_surface)
     {
       _cogl_set_error (error, COGL_WINSYS_ERROR,
@@ -334,10 +338,6 @@ _cogl_winsys_egl_onscreen_init (CoglOnscreen *onscreen,
       return FALSE;
     }
 
-  wayland_onscreen->wayland_shell_surface =
-    wl_shell_get_shell_surface (wayland_renderer->wayland_shell,
-                                wayland_onscreen->wayland_surface);
-
   wayland_onscreen->wayland_egl_native_window =
     wl_egl_window_create (wayland_onscreen->wayland_surface,
                           cogl_framebuffer_get_width (framebuffer),
@@ -358,7 +358,13 @@ _cogl_winsys_egl_onscreen_init (CoglOnscreen *onscreen,
                             wayland_onscreen->wayland_egl_native_window,
                             NULL);
 
-  wl_shell_surface_set_toplevel (wayland_onscreen->wayland_shell_surface);
+  if (!onscreen->foreign_surface)
+    {
+      wayland_onscreen->wayland_shell_surface =
+        wl_shell_get_shell_surface (wayland_renderer->wayland_shell,
+                                    wayland_onscreen->wayland_surface);
+      wl_shell_surface_set_toplevel (wayland_onscreen->wayland_shell_surface);
+    }
 
   return TRUE;
 }
@@ -375,22 +381,24 @@ _cogl_winsys_egl_onscreen_deinit (CoglOnscreen *onscreen)
       wayland_onscreen->wayland_egl_native_window = NULL;
     }
 
-  /* NB: The wayland protocol docs explicitly state that
+  if (!onscreen->foreign_surface)
-   * "wl_shell_surface_destroy() must be called before destroying the
-   * wl_surface object." ... */
-  if (wayland_onscreen->wayland_shell_surface)
     {
-      wl_shell_surface_destroy (wayland_onscreen->wayland_shell_surface);
+      /* NB: The wayland protocol docs explicitly state that
-      wayland_onscreen->wayland_shell_surface = NULL;
+       * "wl_shell_surface_destroy() must be called before destroying
-    }
+       * the wl_surface object." ... */
+      if (wayland_onscreen->wayland_shell_surface)
+        {
+          wl_shell_surface_destroy (wayland_onscreen->wayland_shell_surface);
+          wayland_onscreen->wayland_shell_surface = NULL;
+        }
 
-  if (wayland_onscreen->wayland_surface)
+      if (wayland_onscreen->wayland_surface)
-    {
+        {
-      wl_surface_destroy (wayland_onscreen->wayland_surface);
+          wl_surface_destroy (wayland_onscreen->wayland_surface);
-      wayland_onscreen->wayland_surface = NULL;
+          wayland_onscreen->wayland_surface = NULL;
+        }
     }
 
-
   g_slice_free (CoglOnscreenWayland, wayland_onscreen);
 }
 
@@ -524,7 +532,7 @@ cogl_wayland_onscreen_get_surface (CoglOnscreen *onscreen)
   CoglFramebuffer *fb;
 
   fb = COGL_FRAMEBUFFER (onscreen);
-  if (fb->allocated)
+  if (fb->allocated && !onscreen->foreign_surface)
     {
       CoglOnscreenEGL *egl_onscreen = onscreen->winsys;
       CoglOnscreenWayland *wayland_onscreen = egl_onscreen->platform;
@@ -550,6 +558,18 @@ cogl_wayland_onscreen_get_shell_surface (CoglOnscreen *onscreen)
     return NULL;
 }
 
+void
+cogl_wayland_onscreen_set_foreign_surface (CoglOnscreen *onscreen,
+                                           struct wl_surface *surface)
+{
+  CoglFramebuffer *fb;
+
+  fb = COGL_FRAMEBUFFER (onscreen);
+  _COGL_RETURN_IF_FAIL (!fb->allocated);
+
+  onscreen->foreign_surface = surface;
+}
+
 void
 cogl_wayland_onscreen_resize (CoglOnscreen *onscreen,
                               int           width,