Index: operation.h
===================================================================
--- operation.h	(revision 28844)
+++ operation.h	(revision 28845)
@@ -135,7 +135,7 @@
 
 /* pointer to low-level operation (copy, move and rotate) functions */
 typedef struct {
-	void (*common_pre)(pcb_opctx_t *ctx, pcb_any_obj_t *ptr2, void *ptr3);  /* called before anything else (not object-type-dependent) */
+	int (*common_pre)(pcb_opctx_t *ctx, pcb_any_obj_t *ptr2, void *ptr3);  /* called before anything else (not object-type-dependent); skip the rest of the call for the object if returns 1 */
 	void (*common_post)(pcb_opctx_t *ctx, pcb_any_obj_t *ptr2, void *ptr3); /* called after everything else (not object-type-dependent) */
 
 	void *(*Line)(pcb_opctx_t *ctx, pcb_layer_t *, pcb_line_t *);