pointer-constraints-v1: add cursor_hint.enabled

This allows compositors to check whether the cursor hint is set.

include/wlr/types/wlr_pointer_constraints_v1.h

@@ -33,6 +33,7 @@ struct wlr_pointer_constraint_v1_state {
 
 	// only valid for locked_pointer
 	struct {
+		bool enabled;
 		double x, y;
 	} cursor_hint;
 };

types/wlr_pointer_constraints_v1.c

@@ -97,6 +97,7 @@ static void pointer_constraint_set_cursor_position_hint(struct wl_client *client
 		return;
 	}
 
+	constraint->pending.cursor_hint.enabled = true;
 	constraint->pending.cursor_hint.x = wl_fixed_to_double(x);
 	constraint->pending.cursor_hint.y = wl_fixed_to_double(y);
 	constraint->pending.committed |= WLR_POINTER_CONSTRAINT_V1_STATE_CURSOR_HINT;