main: Add test initialization function

Since Clutter's backend relies on MetaBackend now, initialzation has
to go through meta_init(), both in mutter and in gnome-shell.

However the compositor enum and backend gtype used to enforce the
environment used for tests are private, so instead expose a test
initialization function that can be used from both mutter and
gnome-shell.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/750

src/core/main.c

@@ -87,6 +87,7 @@
 #ifdef HAVE_WAYLAND
 #include "backends/x11/nested/meta-backend-x11-nested.h"
 #include "wayland/meta-wayland.h"
+#include "wayland/meta-xwayland.h"
 #endif
 
 #ifdef HAVE_NATIVE_BACKEND
@@ -741,3 +742,22 @@ meta_get_x11_display_policy (void)
 
   return META_DISPLAY_POLICY_MANDATORY;
 }
+
+void
+meta_test_init (void)
+{
+#if defined(HAVE_WAYLAND)
+  g_autofree char *display_name = g_strdup ("mutter-test-display-XXXXXX");
+  int fd = g_mkstemp (display_name);
+
+  meta_override_compositor_configuration (META_COMPOSITOR_TYPE_WAYLAND,
+                                          META_TYPE_BACKEND_X11_NESTED);
+  meta_wayland_override_display_name (display_name);
+  meta_xwayland_override_display_number (512 + rand() % 512);
+  meta_init ();
+
+  close (fd);
+#else
+  g_error ("Tests require wayland support");
+#endif
+}

src/meta/main.h

@@ -75,4 +75,8 @@ void meta_exit (MetaExitCode code) G_GNUC_NORETURN;
 META_EXPORT
 void meta_quit (MetaExitCode code);
 
+META_EXPORT
+void            meta_test_init               (void);
+
+
 #endif

src/tests/clutter-test-utils.h

@@ -86,13 +86,7 @@ G_BEGIN_DECLS
 int \
 main (int argc, char *argv[]) \
 { \
-  char *display_name = g_strdup ("mutter-test-display-XXXXXX");\
-  int fd = g_mkstemp (display_name);\
-  meta_wayland_override_display_name (display_name);\
-  meta_override_compositor_configuration (META_COMPOSITOR_TYPE_WAYLAND,\
-                                          META_TYPE_BACKEND_X11_NESTED);\
-\
-  meta_init ();\
+  meta_test_init ();\
 \
   clutter_test_init (&argc, &argv); \
 \
@@ -100,8 +94,6 @@ main (int argc, char *argv[]) \
     units \
   } \
 \
-  close (fd);\
-  g_free (display_name);\
   return clutter_test_run (); \
 }