[clutter/multi-backend: 4/16] Allow checking the backend type at run-time

[Emmanuele Bassi <ebassi src gnome org>]

commit 9d3952bc90ca4193e9f992900108fca9f1e8ad91
Author: Emmanuele Bassi <ebassi linux intel com>
Date:   Mon Sep 26 13:14:26 2011 +0100

    Allow checking the backend type at run-time
    
    Portable code should be allowed to check type backend currently being
    used, so that it can use platform-specific API (not just Clutter's).
    
    We don't want to go down the GDK route, with public types for
    ClutterBackend and ClutterStageWindow implementations, and use the type
    system, e.g.:
    
      #ifdef GDK_WINDOWING_X11
        if (GDK_IS_WINDOW_X11 (window))
          use_x11_api (window);
        else
      #endif
      #ifdef GDK_WINDOWING_WIN32
        if (GDK_IS_WINDOW_WIN32 (window))
          use_win32_api (window);
        else
      #endif
        g_critical ("Unsupported backend");
    
    This system would make us expose the backend system, and we want to
    still reserve us the option to change the backend system to increase its
    granularity â e.g. choosing different input event systems regardless of
    the windowing system.
    
    This commit adds a simple function that checks the backend type against
    a symbolic constant â the same constant string that can be used to
    select the backend at run-time through the CLUTTER_BACKEND environment
    variable.

 clutter/clutter-backend.h    |   67 ++++++++++++++++++++++++++++++++++++++++
 clutter/clutter-main.c       |   70 ++++++++++++++++++++++++++++++++++++++---
 clutter/clutter-version.h.in |    2 +
 3 files changed, 133 insertions(+), 6 deletions(-)
---
diff --git a/clutter/clutter-backend.h b/clutter/clutter-backend.h
index 22707fc..c51c8dd 100644
--- a/clutter/clutter-backend.h
+++ b/clutter/clutter-backend.h
@@ -49,6 +49,73 @@ G_BEGIN_DECLS
 #define CLUTTER_IS_BACKEND(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), CLUTTER_TYPE_BACKEND))
 
 /**
+ * CLUTTER_OSX_BACKEND:
+ *
+ * Evaluates to the symbolic name of the Quartz Clutter backend.
+ *
+ * This macro should be used with clutter_check_backend().
+ *
+ * Since: 1.10
+ */
+#define CLUTTER_OSX_BACKEND             "osx"
+
+/**
+ * CLUTTER_X11_BACKEND:
+ *
+ * Evaluates to the symbolic name of the X11 Clutter backend.
+ *
+ * This macro should be used with clutter_check_backend().
+ *
+ * Since: 1.10
+ */
+
+#define CLUTTER_X11_BACKEND             "x11"
+
+/**
+ * CLUTTER_WIN32_BACKEND:
+ *
+ * Evaluates to the symbolic name of the Windows Clutter backend.
+ *
+ * This macro should be used with clutter_check_backend().
+ *
+ * Since: 1.10
+ */
+#define CLUTTER_WIN32_BACKEND           "win32"
+
+/**
+ * CLUTTER_EGL_NATIVE_BACKEND:
+ *
+ * Evaluates to the symbolic name of the EGL framebuffer Clutter backend.
+ *
+ * This macro should be used with clutter_check_backend().
+ *
+ * Since: 1.10
+ */
+#define CLUTTER_EGL_NATIVE_BACKEND      "eglnative"
+
+/**
+ * CLUTTER_WAYLAND_BACKEND:
+ *
+ * Evaluates to the symbolic name of the Wayland client Clutter backend.
+ *
+ * This macro should be used with clutter_check_backend().
+ *
+ * Since: 1.10
+ */
+#define CLUTTER_WAYLAND_BACKEND         "wayland"
+
+/**
+ * CLUTTER_GDK_BACKEND:
+ *
+ * Evaluates to the symbolic name of the GDK Clutter backend.
+ *
+ * This macro should be used with clutter_check_backend().
+ *
+ * Since: 1.10
+ */
+#define CLUTTER_GDK_BACKEND             "gdk"
+
+/**
  * ClutterBackend:
  *
  * <structname>ClutterBackend</structname> is an opaque structure whose
diff --git a/clutter/clutter-main.c b/clutter/clutter-main.c
index f1ed16d..7e4eb62 100644
--- a/clutter/clutter-main.c
+++ b/clutter/clutter-main.c
@@ -1314,32 +1314,32 @@ clutter_context_get_default_unlocked (void)
       backend = g_getenv ("CLUTTER_BACKEND");
 
 #ifdef CLUTTER_WINDOWING_OSX
-      if (backend == NULL || strcmp (backend, "osx") == 0)
+      if (backend == NULL || strcmp (backend, CLUTTER_OSX_BACKEND) == 0)
         ctx->backend = g_object_new (CLUTTER_TYPE_BACKEND_OSX, NULL);
       else
 #endif
 #ifdef CLUTTER_WINDOWING_WIN32
-      if (backend == NULL || strcmp (backend, "win32") == 0)
+      if (backend == NULL || strcmp (backend, CLUTTER_WIN32_BACKEND) == 0)
         ctx->backend = g_object_new (CLUTTER_TYPE_BACKEND_WIN32, NULL);
       else
 #endif
 #ifdef CLUTTER_WINDOWING_WAYLAND
-      if (backend == NULL || strcmp (backend, "wayland") == 0)
+      if (backend == NULL || strcmp (backend, CLUTTER_WAYLAND_BACKEND) == 0)
         ctx->backend = g_object_new (CLUTTER_TYPE_BACKEND_WAYLAND, NULL);
       else
 #endif
 #ifdef CLUTTER_WINDOWING_EGL
-      if (backend == NULL || strcmp (backend, "eglnative") == 0)
+      if (backend == NULL || strcmp (backend, CLUTTER_EGL_NATIVE_BACKEND) == 0)
         ctx->backend = g_object_new (CLUTTER_TYPE_BACKEND_EGLNATIVE, NULL);
       else
 #endif
 #ifdef CLUTTER_WINDOWING_X11
-      if (backend == NULL || strcmp (backend, "x11") == 0)
+      if (backend == NULL || strcmp (backend, CLUTTER_X11_BACKEND) == 0)
         ctx->backend = g_object_new (CLUTTER_TYPE_BACKEND_X11, NULL);
       else
 #endif
 #ifdef CLUTTER_WINDOWING_GDK
-      if (backend == NULL || strcmp (backend, "gdk") == 0)
+      if (backend == NULL || strcmp (backend, CLUTTER_GDK_BACKEND) == 0)
         ctx->backend = g_object_new (CLUTTER_TYPE_BACKEND_GDK, NULL);
       else
 #endif
@@ -3589,3 +3589,61 @@ _clutter_context_get_motion_events_enabled (void)
 
   return context->motion_events_per_actor;
 }
+
+/**
+ * clutter_check_backend:
+ * @backend_type: the name of the backend to check
+ *
+ * Checks the run-time name of the Clutter backend, using the symbolic
+ * macros like %CLUTTER_OSX_BACKEND or %CLUTTER_X11_BACKEND.
+ *
+ * Return value: %TRUE if the current Clutter backend is the one checked,
+ *   and %FALSE otherwise
+ *
+ * Since: 1.10
+ */
+gboolean
+clutter_check_backend (const char *backend_type)
+{
+  ClutterMainContext *context = _clutter_context_get_default ();
+
+  g_return_val_if_fail (backend_type != NULL, FALSE);
+
+#ifdef CLUTTER_WINDOWING_OSX
+  if (strcmp (backend_type, CLUTTER_OSX_BACKEND) == 0 &&
+      CLUTTER_IS_BACKEND_OSX (context->backend))
+    return TRUE;
+  else
+#endif
+#ifdef CLUTTER_WINDOWING_WIN32
+  if (strcmp (backend_type, CLUTTER_WIN32_BACKEND) == 0 &&
+      CLUTTER_IS_BACKEND_WIN32 (context->backend))
+    return TRUE;
+  else
+#endif
+#ifdef CLUTTER_WINDOWING_WAYLAND
+  if (strcmp (backend_type, CLUTTER_WAYLAND_BACKEND) == 0 &&
+      CLUTTER_IS_BACKEND_WAYLAND (context->backend))
+    return TRUE;
+  else
+#endif
+#ifdef CLUTTER_WINDOWING_EGL
+  if (strcmp (backend_type, CLUTTER_EGL_BACKEND) == 0 &&
+      CLUTTER_IS_BACKEND_EGL_NATIVE (context->backend))
+    return TRUE;
+  else
+#endif
+#ifdef CLUTTER_WINDOWING_X11
+  if (strcmp (backend_type, CLUTTER_X11_BACKEND) == 0 &&
+      CLUTTER_IS_BACKEND_X11 (context->backend))
+    return TRUE;
+  else
+#endif
+#ifdef CLUTTER_WINDOWING_GDK
+  if (strcmp (backend_type, CLUTTER_GDK_BACKEND) == 0 &&
+      CLUTTER_IS_BACKEND_GDK (context->backend))
+    return TRUE;
+  else
+#endif
+  return FALSE;
+}
diff --git a/clutter/clutter-version.h.in b/clutter/clutter-version.h.in
index 835e29f..5b38ee0 100644
--- a/clutter/clutter-version.h.in
+++ b/clutter/clutter-version.h.in
@@ -195,6 +195,8 @@ gboolean clutter_check_version (guint major,
                                 guint minor,
                                 guint micro);
 
+gboolean clutter_check_backend (const char *backend_type);
+
 G_END_DECLS
 
 #endif /* __CLUTTER_VERSION_H__ */