plugin-manager: Guard MetaPluginClass.xevent_filter

As we are getting close to have a Wayland-only build, guard those usages
so we don't 'regress'.
Once Kiosk figures it use case, we can revert both this commit and the
previous one.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3652>

src/backends/x11/meta-backend-x11.c

@@ -348,9 +348,11 @@ handle_host_xevent (MetaBackend *backend,
   MetaBackendX11Private *priv = meta_backend_x11_get_instance_private (x11);
   ClutterBackend *clutter_backend = meta_backend_get_clutter_backend (backend);
   ClutterSeat *seat = clutter_backend_get_default_seat (clutter_backend);
-  MetaContext *context = meta_backend_get_context (backend);
   gboolean bypass_clutter = FALSE;
+#ifdef HAVE_X11
+  MetaContext *context = meta_backend_get_context (backend);
   MetaDisplay *display;
+#endif
 
   switch (event->type)
     {
@@ -365,6 +367,7 @@ handle_host_xevent (MetaBackend *backend,
 
   XGetEventData (priv->xdisplay, &event->xcookie);
 
+#ifdef HAVE_X11
   display = meta_context_get_display (context);
   if (display)
     {
@@ -375,6 +378,7 @@ handle_host_xevent (MetaBackend *backend,
       if (meta_plugin_manager_xevent_filter (plugin_mgr, event))
         bypass_clutter = TRUE;
     }
+#endif
 
   bypass_clutter = (meta_backend_x11_handle_host_xevent (x11, event) ||
                     bypass_clutter);

src/compositor/meta-plugin-manager.c

@@ -26,7 +26,6 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "backends/x11/meta-clutter-backend-x11.h"
 #include "compositor/compositor-private.h"
 #include "compositor/meta-module.h"
 #include "core/meta-inhibit-shortcuts-dialog-default-private.h"
@@ -332,6 +331,7 @@ meta_plugin_manager_filter_keybinding (MetaPluginManager *plugin_mgr,
   return FALSE;
 }
 
+#ifdef HAVE_X11
 gboolean
 meta_plugin_manager_xevent_filter (MetaPluginManager *plugin_mgr,
                                    XEvent            *xev)
@@ -340,6 +340,7 @@ meta_plugin_manager_xevent_filter (MetaPluginManager *plugin_mgr,
 
   return _meta_plugin_xevent_filter (plugin, xev);
 }
+#endif
 
 void
 meta_plugin_manager_confirm_display_change (MetaPluginManager *plugin_mgr)

src/compositor/meta-plugin-manager.h

@@ -70,10 +70,12 @@ gboolean meta_plugin_manager_switch_workspace (MetaPluginManager   *mgr,
 gboolean meta_plugin_manager_filter_keybinding (MetaPluginManager  *mgr,
                                                 MetaKeyBinding     *binding);
 
+#ifdef HAVE_X11
 gboolean meta_plugin_manager_xevent_filter (MetaPluginManager *mgr,
                                             XEvent            *xev);
 gboolean _meta_plugin_xevent_filter (MetaPlugin *plugin,
                                      XEvent     *xev);
+#endif
 
 void     meta_plugin_manager_confirm_display_change (MetaPluginManager *mgr);
 

src/compositor/meta-plugin.c

@@ -30,12 +30,16 @@
 #include "meta/meta-plugin.h"
 
 #include <string.h>
+#ifdef HAVE_X11
 #include <X11/Xlib.h>
 #include <X11/extensions/Xfixes.h>
 #include <X11/extensions/shape.h>
+#endif
 
-#include "backends/meta-monitor-manager-private.h"
+#ifdef HAVE_X11
 #include "backends/x11/meta-clutter-backend-x11.h"
+#endif
+#include "backends/meta-monitor-manager-private.h"
 #include "compositor/compositor-private.h"
 #include "compositor/meta-window-actor-private.h"
 #include "compositor/meta-plugin-manager.h"
@@ -71,6 +75,7 @@ meta_plugin_get_info (MetaPlugin *plugin)
   return NULL;
 }
 
+#ifdef HAVE_X11
 gboolean
 _meta_plugin_xevent_filter (MetaPlugin *plugin,
                             XEvent     *xev)
@@ -82,6 +87,7 @@ _meta_plugin_xevent_filter (MetaPlugin *plugin,
   else
     return FALSE;
 }
+#endif
 
 void
 meta_plugin_switch_workspace_completed (MetaPlugin *plugin)

src/meta/meta-plugin.h

@@ -21,7 +21,6 @@
 
 #pragma once
 
-#include <X11/extensions/Xfixes.h>
 #include <gmodule.h>
 
 #include "clutter/clutter.h"
@@ -38,6 +37,9 @@ G_DECLARE_DERIVABLE_TYPE (MetaPlugin, meta_plugin, META, PLUGIN, GObject)
 
 typedef struct _MetaPluginInfo    MetaPluginInfo;
 
+/* Allows us to keep the xevent_filter vfunc even when building Mutter without X11 */
+typedef union _XEvent XEvent;
+
 /**
  * MetaPluginClass:
  * @start: virtual function called when the compositor starts managing a screen