From d1ee5c340237cb64b18cc4fdef91bc472eb415ef Mon Sep 17 00:00:00 2001

From: "Owen W. Taylor" <otaylor@fishsoup.net>

Date: Thu, 8 May 2014 18:52:09 -0400

Subject: [PATCH] Allow setting up quad-buffer stereo output

Add clutter_x11_set_use_stereo_stage() that can be called

before clutter_init() so that the CoglDisplay we create and all

stages created from that CoglDisplay will be created with a

stereo fbconfig.

This is done in clutter-x11 because of the similarity to the

existing clutter_x11_set_use_argb_visual(), and because it's

not clear without other examples whether the need to have

stereo enabled from before clutter_init() is universal or

somethign specific to GLX.

https://bugzilla.gnome.org/show_bug.cgi?id=732706

---

 clutter/x11/clutter-backend-x11.c | 168 +++++++++++++++++++++++++++++---------

 clutter/x11/clutter-x11.h         |   3 +

 2 files changed, 131 insertions(+), 40 deletions(-)

diff --git a/clutter/x11/clutter-backend-x11.c b/clutter/x11/clutter-backend-x11.c

index c9478c4..14eda35 100644

--- a/clutter/x11/clutter-backend-x11.c

+++ b/clutter/x11/clutter-backend-x11.c

@@ -93,6 +93,7 @@ static const gchar *atom_names[] = {

 static gboolean _no_xevent_retrieval = FALSE;

 static gboolean clutter_enable_xinput = TRUE;

 static gboolean clutter_enable_argb = FALSE;

+static gboolean clutter_enable_stereo = FALSE;

 static Display  *_foreign_dpy = NULL;

 /* options */

@@ -688,6 +689,59 @@ clutter_backend_x11_get_renderer (ClutterBackend  *backend,

   return renderer;

 }

+static gboolean

+check_onscreen_template (CoglRenderer         *renderer,

+                         CoglSwapChain        *swap_chain,

+                         CoglOnscreenTemplate *onscreen_template,

+                         CoglBool              enable_argb,

+                         CoglBool              enable_stereo,

+                         GError              **error)

+{

+  GError *internal_error = NULL;

+

+  cogl_swap_chain_set_has_alpha (swap_chain, enable_argb);

+  cogl_onscreen_template_set_stereo_enabled (onscreen_template,

+					     clutter_enable_stereo);

+

+  /* cogl_renderer_check_onscreen_template() is actually just a

+   * shorthand for creating a CoglDisplay, and calling

+   * cogl_display_setup() on it, then throwing the display away. If we

+   * could just return that display, then it would be more efficient

+   * not to use cogl_renderer_check_onscreen_template(). However, the

+   * backend API requires that we return an CoglDisplay that has not

+   * yet been setup, so one way or the other we'll have to discard the

+   * first display and make a new fresh one.

+   */

+  if (cogl_renderer_check_onscreen_template (renderer, onscreen_template, &internal_error))

+    {

+      clutter_enable_argb = enable_argb;

+      clutter_enable_stereo = enable_stereo;

+

+      return TRUE;

+    }

+  else

+    {

+      if (enable_argb || enable_stereo) /* More possibilities to try */

+        CLUTTER_NOTE (BACKEND,

+                      "Creation of a CoglDisplay with alpha=%s, stereo=%s failed: %s",

+                      enable_argb ? "enabled" : "disabled",

+                      enable_stereo ? "enabled" : "disabled",

+                      internal_error != NULL

+                        ?  internal_error->message

+                        : "Unknown reason");

+      else

+        g_set_error_literal (error, CLUTTER_INIT_ERROR,

+                             CLUTTER_INIT_ERROR_BACKEND,

+                             internal_error != NULL

+                               ? internal_error->message

+                               : "Creation of a CoglDisplay failed");

+

+      g_clear_error (&internal_error);

+

+      return FALSE;

+    }

+}

+

 static CoglDisplay *

 clutter_backend_x11_get_display (ClutterBackend  *backend,

                                  CoglRenderer    *renderer,

@@ -695,56 +749,38 @@ clutter_backend_x11_get_display (ClutterBackend  *backend,

                                  GError         **error)

 {

   CoglOnscreenTemplate *onscreen_template;

-  GError *internal_error = NULL;

-  CoglDisplay *display;

-  gboolean res;

-

-  CLUTTER_NOTE (BACKEND, "Alpha on Cogl swap chain: %s",

-                clutter_enable_argb ? "enabled" : "disabled");

+  CoglDisplay *display = NULL;

+  gboolean res = FALSE;

-  cogl_swap_chain_set_has_alpha (swap_chain, clutter_enable_argb);

+  CLUTTER_NOTE (BACKEND, "Creating CoglDisplay, alpha=%s, stereo=%s",

+                clutter_enable_argb ? "enabled" : "disabled",

+                clutter_enable_stereo ? "enabled" : "disabled");

   onscreen_template = cogl_onscreen_template_new (swap_chain);

-  res = cogl_renderer_check_onscreen_template (renderer,

-                                               onscreen_template,

-                                               &internal_error);

-  if (!res && clutter_enable_argb)

-    {

-      CLUTTER_NOTE (BACKEND,

-                    "Creation of a context with a ARGB visual failed: %s",

-                    internal_error != NULL ? internal_error->message

-                                           : "Unknown reason");

+  /* It's possible that the current renderer doesn't support transparency

+   * or doesn't support stereo, so we try the different combinations.

+   */

+  if (clutter_enable_argb && clutter_enable_stereo)

+    res = check_onscreen_template (renderer, swap_chain, onscreen_template,

+                                  TRUE, TRUE, error);

-      g_clear_error (&internal_error);

+  /* Prioritize stereo over alpha */

+  if (!res && clutter_enable_stereo)

+    res = check_onscreen_template (renderer, swap_chain, onscreen_template,

+                                  FALSE, TRUE, error);

-      /* It's possible that the current renderer doesn't support transparency

-       * in a swap_chain so lets see if we can fallback to not having any

-       * transparency...

-       *

-       * XXX: It might be nice to have a CoglRenderer feature we could

-       * explicitly check for ahead of time.

-       */

-      clutter_enable_argb = FALSE;

-      cogl_swap_chain_set_has_alpha (swap_chain, FALSE);

-      res = cogl_renderer_check_onscreen_template (renderer,

-                                                   onscreen_template,

-                                                   &internal_error);

-    }

+  if (!res && clutter_enable_argb)

+    res = check_onscreen_template (renderer, swap_chain, onscreen_template,

+                                  TRUE, FALSE, error);

   if (!res)

-    {

-      g_set_error_literal (error, CLUTTER_INIT_ERROR,

-                           CLUTTER_INIT_ERROR_BACKEND,

-                           internal_error->message);

+    res = check_onscreen_template (renderer, swap_chain, onscreen_template,

+                                  FALSE, FALSE, error);

-      g_error_free (internal_error);

-      cogl_object_unref (onscreen_template);

+  if (res)

+    display = cogl_display_new (renderer, onscreen_template);

-      return NULL;

-    }

-

-  display = cogl_display_new (renderer, onscreen_template);

   cogl_object_unref (onscreen_template);

   return display;

@@ -1303,6 +1339,58 @@ clutter_x11_get_use_argb_visual (void)

   return clutter_enable_argb;

 }

+/**

+ * clutter_x11_set_use_stereo_stage:

+ * @use_stereo: %TRUE if the stereo stages should be used if possible.

+ *

+ * Sets whether the backend object for Clutter stages, will,

+ * if possible, be created with the ability to support stereo drawing

+ * (drawing separate images for the left and right eyes).

+ *

+ * This function must be called before clutter_init() is called.

+ * During paint callbacks, cogl_framebuffer_is_stereo() can be called

+ * on the framebuffer retrieved by cogl_get_draw_framebuffer() to

+ * determine if stereo support was successfully enabled, and

+ * cogl_framebuffer_set_stereo_mode() to determine which buffers

+ * will be drawn to.

+ *

+ * Note that this function *does not* cause the stage to be drawn

+ * multiple times with different perspective transformations and thus

+ * appear in 3D, it simply enables individual ClutterActors to paint

+ * different images for the left and and right eye.

+ *

+ */

+void

+clutter_x11_set_use_stereo_stage (gboolean use_stereo)

+{

+  if (_clutter_context_is_initialized ())

+    {

+      g_warning ("%s() can only be used before calling clutter_init()",

+                 G_STRFUNC);

+      return;

+    }

+

+  CLUTTER_NOTE (BACKEND, "STEREO stages are %s",

+                use_stereo ? "enabled" : "disabled");

+

+  clutter_enable_stereo = use_stereo;

+}

+

+/**

+ * clutter_x11_get_use_stereo_stage:

+ *

+ * Retrieves whether the Clutter X11 backend will create stereo

+ * stages if possible.

+ *

+ * Return value: %TRUE if stereo stages are used if possible

+ *

+ */

+gboolean

+clutter_x11_get_use_stereo_stage (void)

+{

+  return clutter_enable_stereo;

+}

+

 XVisualInfo *

 _clutter_backend_x11_get_visual_info (ClutterBackendX11 *backend_x11)

 {

diff --git a/clutter/x11/clutter-x11.h b/clutter/x11/clutter-x11.h

index b0ab8a1..4fb2b35 100644

--- a/clutter/x11/clutter-x11.h

+++ b/clutter/x11/clutter-x11.h

@@ -156,6 +156,9 @@ void     clutter_x11_set_use_argb_visual (gboolean use_argb);

 CLUTTER_AVAILABLE_IN_ALL

 gboolean clutter_x11_get_use_argb_visual (void);

+void     clutter_x11_set_use_stereo_stage (gboolean use_stereo);

+gboolean clutter_x11_get_use_stereo_stage (void);

+

 CLUTTER_AVAILABLE_IN_ALL

 Time clutter_x11_get_current_event_time (void);

-- 

2.1.0