backends: Unify touch sequence to slot conversion

We had code in both backends that sort of independently associated
sequences to slots. Make both transform slots to sequences the same
way, so they may share the implementation convert those back to slots.

This helper now lives in Clutter API.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1623>

clutter/clutter/clutter-event.c

@@ -2134,3 +2134,11 @@ clutter_event_get_event_code (const ClutterEvent *event)
 
   return 0;
 }
+
+int32_t
+clutter_event_sequence_get_slot (const ClutterEventSequence *sequence)
+{
+  g_return_val_if_fail (sequence != NULL, -1);
+
+  return GPOINTER_TO_INT (sequence) - 1;
+}

clutter/clutter/clutter-event.h

@@ -788,6 +788,9 @@ gboolean                 clutter_event_get_pad_event_details         (const Clut
 CLUTTER_EXPORT
 uint32_t                 clutter_event_get_event_code                (const ClutterEvent     *event);
 
+CLUTTER_EXPORT
+int32_t                  clutter_event_sequence_get_slot (const ClutterEventSequence *sequence);
+
 G_END_DECLS
 
 #endif /* __CLUTTER_EVENT_H__ */

src/backends/native/meta-event-native.c

@@ -154,23 +154,3 @@ meta_event_native_get_relative_motion (const ClutterEvent *event,
   else
     return FALSE;
 }
-
-/**
- * meta_event_native_sequence_get_slot:
- * @sequence: a #ClutterEventSequence
- *
- * Retrieves the touch slot triggered by this @sequence
- *
- * Returns: the libinput touch slot.
- *
- * Since: 1.20
- * Stability: unstable
- **/
-int32_t
-meta_event_native_sequence_get_slot (const ClutterEventSequence *sequence)
-{
-  if (!sequence)
-    return -1;
-
-  return GPOINTER_TO_INT (sequence) - 1;
-}

src/backends/native/meta-event-native.h

@@ -42,6 +42,4 @@ gboolean          meta_event_native_get_relative_motion (const ClutterEvent *eve
                                                          double             *dx_unaccel,
                                                          double             *dy_unaccel);
 
-int32_t           meta_event_native_sequence_get_slot (const ClutterEventSequence *sequence);
-
 #endif /* META_EVENT_NATIVE_H */

src/backends/native/meta-seat-impl.c

@@ -2890,7 +2890,7 @@ meta_seat_impl_query_state (MetaSeatImpl         *seat_impl,
       MetaTouchState *touch_state;
       int slot;
 
-      slot = meta_event_native_sequence_get_slot (sequence);
+      slot = clutter_event_sequence_get_slot (sequence);
       touch_state = meta_seat_impl_lookup_touch_state_in_impl (seat_impl, slot);
       if (!touch_state)
         goto out;

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

@@ -691,7 +691,7 @@ meta_backend_x11_finish_touch_sequence (MetaBackend          *backend,
 
   XIAllowTouchEvents (priv->xdisplay,
                       META_VIRTUAL_CORE_POINTER_ID,
-                      meta_x11_event_sequence_get_touch_detail (sequence),
+                      clutter_event_sequence_get_slot (sequence),
                       DefaultRootWindow (priv->xdisplay), event_mode);
 
   if (state == META_SEQUENCE_REJECTED)

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

@@ -113,11 +113,3 @@ out:
 
   return result;
 }
-
-guint
-meta_x11_event_sequence_get_touch_detail (const ClutterEventSequence *sequence)
-{
-  g_return_val_if_fail (sequence != NULL, 0);
-
-  return GPOINTER_TO_UINT (sequence);
-}

src/backends/x11/meta-event-x11.h

@@ -28,8 +28,6 @@
 
 #include "clutter/x11/clutter-x11.h"
 
-guint meta_x11_event_sequence_get_touch_detail (const ClutterEventSequence *sequence);
-
 ClutterX11FilterReturn meta_x11_handle_event (XEvent *xevent);
 
 #endif /* META_EVENT_X11_H */

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

@@ -2213,7 +2213,8 @@ meta_seat_x11_translate_event (MetaSeatX11  *seat,
                                              GUINT_TO_POINTER (xev->detail));
           }
 
-        event->touch.sequence = GUINT_TO_POINTER (xev->detail);
+        /* "NULL" sequences are special cased in clutter */
+        event->touch.sequence = GINT_TO_POINTER (MAX (1, xev->detail + 1));
 
         if (xev->flags & XITouchEmulatingPointer)
           _clutter_event_set_pointer_emulated (event, TRUE);
@@ -2242,7 +2243,8 @@ meta_seat_x11_translate_event (MetaSeatX11  *seat,
         event->touch.type = event->type = CLUTTER_TOUCH_UPDATE;
         event->touch.stage = stage;
         event->touch.time = xev->time;
-        event->touch.sequence = GUINT_TO_POINTER (xev->detail);
+        /* "NULL" sequences are special cased in clutter */
+        event->touch.sequence = GINT_TO_POINTER (MAX (1, xev->detail + 1));
         translate_coords (stage_x11, xev->event_x, xev->event_y, &event->touch.x, &event->touch.y);
 
         clutter_event_set_source_device (event, source_device);

src/wayland/meta-wayland-touch.c

@@ -188,7 +188,7 @@ touch_get_info (MetaWaylandTouch     *touch,
   if (!touch_info && create)
     {
       touch_info = g_new0 (MetaWaylandTouchInfo, 1);
-      touch_info->slot = meta_event_native_sequence_get_slot (sequence);
+      touch_info->slot = clutter_event_sequence_get_slot (sequence);
       g_hash_table_insert (touch->touches, sequence, touch_info);
     }