[clutter/clutter-1.16] Add API to restrict the windowing backend to load

[Giovanni Campagna <gcampagna src gnome org>]

commit da3e6988ad7259e65bbb051589c1adb0d11421d0
Author: Giovanni Campagna <gcampagn redhat com>
Date:   Tue Sep 10 18:29:28 2013 +0200

    Add API to restrict the windowing backend to load
    
    In situations when the default backend would fail (for example
    when compiled with X11 support but run without DISPLAY), or
    when the application is using backend specific code, it makes
    sense to let the application choose the backend explicitly.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=707869

 clutter/clutter-backend-private.h |    2 +
 clutter/clutter-backend.c         |   78 ++++++++++++++++++++++++++++++++++++-
 clutter/clutter-backend.h         |    3 +
 clutter/clutter-main.c            |   49 +----------------------
 clutter/clutter.symbols           |    1 +
 5 files changed, 83 insertions(+), 50 deletions(-)
---
diff --git a/clutter/clutter-backend-private.h b/clutter/clutter-backend-private.h
index 72563a3..d18d6da 100644
--- a/clutter/clutter-backend-private.h
+++ b/clutter/clutter-backend-private.h
@@ -99,6 +99,8 @@ struct _ClutterBackendClass
   void (* settings_changed)   (ClutterBackend *backend);
 };
 
+ClutterBackend *        _clutter_create_backend                         (void);
+
 ClutterStageWindow *    _clutter_backend_create_stage                   (ClutterBackend         *backend,
                                                                          ClutterStage           *wrapper,
                                                                          GError                **error);
diff --git a/clutter/clutter-backend.c b/clutter/clutter-backend.c
index a30a693..2b6c429 100644
--- a/clutter/clutter-backend.c
+++ b/clutter/clutter-backend.c
@@ -83,6 +83,9 @@
 /* XXX - should probably warn, here */
 #include "tslib/clutter-event-tslib.h"
 #endif
+#ifdef CLUTTER_WINDOWING_EGL
+#include "egl/clutter-backend-eglnative.h"
+#endif
 #ifdef CLUTTER_INPUT_WAYLAND
 #include "wayland/clutter-device-manager-wayland.h"
 #endif
@@ -126,6 +129,7 @@ static guint backend_signals[LAST_SIGNAL] = { 0, };
 static struct wl_display *_wayland_compositor_display;
 #endif
 
+static const char *allowed_backend;
 
 static void
 clutter_backend_dispose (GObject *gobject)
@@ -463,6 +467,58 @@ clutter_backend_real_create_stage (ClutterBackend  *backend,
                        NULL);
 }
 
+ClutterBackend *
+_clutter_create_backend (void)
+{
+  const char *backend = allowed_backend;
+  ClutterBackend *retval = NULL;
+
+  if (backend == NULL)
+    {
+      const char *backend_env = g_getenv ("CLUTTER_BACKEND");
+
+      if (backend_env != NULL)
+       backend = g_intern_string (backend_env);
+    }
+
+#ifdef CLUTTER_WINDOWING_OSX
+  if (backend == NULL || backend == I_(CLUTTER_WINDOWING_OSX))
+    retval = g_object_new (CLUTTER_TYPE_BACKEND_OSX, NULL);
+  else
+#endif
+#ifdef CLUTTER_WINDOWING_WIN32
+  if (backend == NULL || backend == I_(CLUTTER_WINDOWING_WIN32))
+    retval = g_object_new (CLUTTER_TYPE_BACKEND_WIN32, NULL);
+  else
+#endif
+#ifdef CLUTTER_WINDOWING_X11
+  if (backend == NULL || backend == I_(CLUTTER_WINDOWING_X11))
+    retval = g_object_new (CLUTTER_TYPE_BACKEND_X11, NULL);
+  else
+#endif
+#ifdef CLUTTER_WINDOWING_WAYLAND
+  if (backend == NULL || backend == I_(CLUTTER_WINDOWING_WAYLAND))
+    retval = g_object_new (CLUTTER_TYPE_BACKEND_WAYLAND, NULL);
+  else
+#endif
+#ifdef CLUTTER_WINDOWING_EGL
+  if (backend == NULL || backend == I_(CLUTTER_WINDOWING_EGL))
+    retval = g_object_new (CLUTTER_TYPE_BACKEND_EGL_NATIVE, NULL);
+  else
+#endif
+#ifdef CLUTTER_WINDOWING_GDK
+  if (backend == NULL || backend == I_(CLUTTER_WINDOWING_GDK))
+    retval = g_object_new (CLUTTER_TYPE_BACKEND_GDK, NULL);
+  else
+#endif
+  if (backend == NULL)
+    g_error ("No default Clutter backend found.");
+  else
+    g_error ("Unsupported Clutter backend: '%s'", backend);
+
+  return retval;
+}
+
 static void
 clutter_backend_real_init_events (ClutterBackend *backend)
 {
@@ -506,8 +562,8 @@ clutter_backend_real_init_events (ClutterBackend *backend)
 #endif
 #ifdef CLUTTER_INPUT_EVDEV
   /* Evdev can be used regardless of the windowing system */
-  if (input_backend != NULL &&
-      strcmp (input_backend, CLUTTER_INPUT_EVDEV) == 0)
+  if ((input_backend != NULL && strcmp (input_backend, CLUTTER_INPUT_EVDEV) == 0) ||
+      clutter_check_windowing_backend (CLUTTER_WINDOWING_EGL))
     {
       _clutter_events_evdev_init (backend);
     }
@@ -1326,3 +1382,21 @@ clutter_wayland_set_compositor_display (void *display)
   _wayland_compositor_display = display;
 }
 #endif
+
+/**
+ * clutter_set_windowing_backend:
+ * @first_backend: the name of a clutter window backend
+ *
+ * Restricts clutter to only use the specified backend.
+ * This must be called before the first API call to clutter, including
+ * clutter_get_option_context()
+ *
+ * Since: 1.16
+ */
+void
+clutter_set_windowing_backend (const char *backend_type)
+{
+  g_return_if_fail (backend_type != NULL);
+
+  allowed_backend = g_intern_string (backend_type);
+}
diff --git a/clutter/clutter-backend.h b/clutter/clutter-backend.h
index 474c426..8f900b7 100644
--- a/clutter/clutter-backend.h
+++ b/clutter/clutter-backend.h
@@ -59,6 +59,9 @@ GType clutter_backend_get_type    (void) G_GNUC_CONST;
 
 ClutterBackend *clutter_get_default_backend (void);
 
+CLUTTER_AVAILABLE_IN_1_16
+void           clutter_set_windowing_backend (const char *backend_type);
+
 gdouble                     clutter_backend_get_resolution            (ClutterBackend             *backend);
 
 void                        clutter_backend_set_font_options          (ClutterBackend             *backend,
diff --git a/clutter/clutter-main.c b/clutter/clutter-main.c
index d0d6185..ef83665 100644
--- a/clutter/clutter-main.c
+++ b/clutter/clutter-main.c
@@ -1390,53 +1390,6 @@ _clutter_context_is_initialized (void)
   return ClutterCntx->is_initialized;
 }
 
-static ClutterBackend *
-clutter_create_backend (void)
-{
-  const char *backend = g_getenv ("CLUTTER_BACKEND");
-  ClutterBackend *retval = NULL;
-
-  if (backend != NULL)
-    backend = g_intern_string (backend);
-
-#ifdef CLUTTER_WINDOWING_OSX
-  if (backend == NULL || backend == I_(CLUTTER_WINDOWING_OSX))
-    retval = g_object_new (CLUTTER_TYPE_BACKEND_OSX, NULL);
-  else
-#endif
-#ifdef CLUTTER_WINDOWING_WIN32
-  if (backend == NULL || backend == I_(CLUTTER_WINDOWING_WIN32))
-    retval = g_object_new (CLUTTER_TYPE_BACKEND_WIN32, NULL);
-  else
-#endif
-#ifdef CLUTTER_WINDOWING_X11
-  if (backend == NULL || backend == I_(CLUTTER_WINDOWING_X11))
-    retval = g_object_new (CLUTTER_TYPE_BACKEND_X11, NULL);
-  else
-#endif
-#ifdef CLUTTER_WINDOWING_WAYLAND
-  if (backend == NULL || backend == I_(CLUTTER_WINDOWING_WAYLAND))
-    retval = g_object_new (CLUTTER_TYPE_BACKEND_WAYLAND, NULL);
-  else
-#endif
-#ifdef CLUTTER_WINDOWING_EGL
-  if (backend == NULL || backend == I_(CLUTTER_WINDOWING_EGL))
-    retval = g_object_new (CLUTTER_TYPE_BACKEND_EGL_NATIVE, NULL);
-  else
-#endif
-#ifdef CLUTTER_WINDOWING_GDK
-  if (backend == NULL || backend == I_(CLUTTER_WINDOWING_GDK))
-    retval = g_object_new (CLUTTER_TYPE_BACKEND_GDK, NULL);
-  else
-#endif
-  if (backend == NULL)
-    g_error ("No default Clutter backend found.");
-  else
-    g_error ("Unsupported Clutter backend: '%s'", backend);
-
-  return retval;
-}
-
 static ClutterMainContext *
 clutter_context_get_default_unlocked (void)
 {
@@ -1449,7 +1402,7 @@ clutter_context_get_default_unlocked (void)
       ctx->is_initialized = FALSE;
 
       /* create the windowing system backend */
-      ctx->backend = clutter_create_backend ();
+      ctx->backend = _clutter_create_backend ();
 
       /* create the default settings object, and store a back pointer to
        * the backend singleton
diff --git a/clutter/clutter.symbols b/clutter/clutter.symbols
index 7b4bffd..7226492 100644
--- a/clutter/clutter.symbols
+++ b/clutter/clutter.symbols
@@ -1193,6 +1193,7 @@ clutter_settings_get_type
 clutter_set_default_frame_rate
 clutter_set_font_flags
 clutter_set_motion_events_enabled
+clutter_set_windowing_backend
 clutter_shader_compile
 clutter_shader_effect_get_program
 clutter_shader_effect_get_shader