Index: trunk/src/libcschem/abstract.c
===================================================================
--- trunk/src/libcschem/abstract.c	(revision 777)
+++ trunk/src/libcschem/abstract.c	(revision 778)
@@ -111,6 +111,7 @@
 	fprintf(f, "%s%sAttributes:\n", prefix1, prefix2);
 	for(e = htsp_first(attr); e != NULL; e = htsp_next(attr, e)) {
 		const csch_attrib_t *a = e->value;
+		if (a->deleted) continue;
 		fprintf(f, "%s%s %s=%s\n", prefix1, prefix2, a->key, a->val);
 	}
 }
Index: trunk/src/libcschem/attrib.c
===================================================================
--- trunk/src/libcschem/attrib.c	(revision 777)
+++ trunk/src/libcschem/attrib.c	(revision 778)
@@ -2,7 +2,7 @@
  *                            COPYRIGHT
  *
  *  cschem - modular/flexible schematics editor - libcschem (core library)
- *  Copyright (C) 2018 Tibor 'Igor2' Palinkas
+ *  Copyright (C) 2018,2019 Tibor 'Igor2' Palinkas
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Lesser General Public
@@ -176,3 +176,16 @@
 
 	return dst;
 }
+
+int csch_attrib_del(csch_attribs_t *attribs, int prio, const char *key, const csch_source_arg_t source)
+{
+	csch_attrib_t *a = htsp_get((csch_attribs_t *)attribs, key);
+	if (a == NULL)
+		return -1;
+
+	a->deleted = 1;
+	append_src(a, prio, source, 0);
+}
+
+
+
Index: trunk/src/libcschem/attrib.h
===================================================================
--- trunk/src/libcschem/attrib.h	(revision 777)
+++ trunk/src/libcschem/attrib.h	(revision 778)
@@ -41,6 +41,8 @@
 	char *key;
 	int prio;
 
+	unsigned int deleted:1;
+
 	char *val;  /* scalar; if NULL, use arr */
 	vts0_t arr;
 	vts0_t source;
@@ -93,9 +95,9 @@
 
 /* Del a key from an attribute hash; if history is not NULL, the key is kept
    and the value is emptied so source history is preserved. */
-int csch_attrib_del(csch_attribs_t *attribs, int prio, const char *key, const char *source);
-int csch_attrib_delptr(csch_attribs_t *attribs, int prio, const char *key, char *source);
+int csch_attrib_del(csch_attribs_t *attribs, int prio, const char *key, const csch_source_arg_t source);
 
+
 /* Build an ordered list of attributes; vector items point to
    (const csch_attrib_t *) */
 void csch_attrib_sort(vtp0_t *dst, const csch_attribs_t *attribs);
@@ -108,7 +110,7 @@
 csch_inline const char *csch_attrib_get_str(csch_attribs_t *attribs, const char *key)
 {
 	csch_attrib_t *a = csch_attrib_get(attribs, key);
-	if (a == NULL) return NULL;
+	if ((a == NULL) || (a->deleted)) return NULL;
 	return a->val;
 }
 
@@ -115,7 +117,7 @@
 csch_inline const vts0_t *csch_attrib_get_arr(csch_attribs_t *attribs, const char *key)
 {
 	csch_attrib_t *a = csch_attrib_get(attribs, key);
-	if (a != NULL) return NULL;
+	if ((a != NULL) || (a->deleted)) return NULL;
 	return &a->arr;
 }
 
Index: trunk/src/libcschem/engine.c
===================================================================
--- trunk/src/libcschem/engine.c	(revision 777)
+++ trunk/src/libcschem/engine.c	(revision 778)
@@ -75,12 +75,12 @@
 
 /* returns argc or -1 on error; arguments are packed starting from skip_first+1,
    making room for caller supplied arguments before argv[1] if skip_first > 0 */
-static int eng_load_args(csch_sheet_t *sheet, fgw_arg_t *argv, int max_argc, va_list ap, int skip_first)
+static int eng_load_args(csch_hook_call_ctx_t *cctx, fgw_arg_t *argv, int max_argc, va_list ap, int skip_first)
 {
 	int argc;
 
 	argv[0].type = FGW_FUNC;
-	argv[0].val.argv0.user_call_ctx = sheet;
+	argv[0].val.argv0.user_call_ctx = cctx;
 
 	for(argc = 1 + skip_first;;argc++) {
 		fgw_type_t type = va_arg(ap, fgw_type_t);
@@ -127,6 +127,7 @@
 	long n;
 	const char *sres;
 	fgw_arg_t argv[MAX_ARGS], ares;
+	csch_hook_call_ctx_t cctx;
 
 	v = vtp0_get(&proj->views, proj->curr, 0);
 	if (v == NULL)
@@ -134,7 +135,7 @@
 	view = *v;
 
 	va_start(ap, defval);
-	argc = eng_load_args(sheet, argv, (sizeof(argv)/sizeof(argv[0])), ap, 1);
+	argc = eng_load_args(&cctx, argv, (sizeof(argv)/sizeof(argv[0])), ap, 1);
 	va_end(ap);
 	if (argc < 0)
 		goto error;
@@ -141,6 +142,7 @@
 
 
 	sres = defval;
+	cctx.sheet = sheet;
 
 	for(n = 0; n < view->engines.used; n++) {
 		csch_view_eng_t *eng = view->engines.array[n];
@@ -148,6 +150,7 @@
 		if (hk == NULL)
 			continue;
 
+		cctx.view_eng = eng;
 		ares.type = FGW_INT;
 		ares.val.nat_int = 0;
 		argv[0].val.argv0.func = hk;
@@ -185,6 +188,7 @@
 	int argc;
 	long n;
 	fgw_arg_t argv[MAX_ARGS], ares;
+	csch_hook_call_ctx_t cctx;
 
 	v = vtp0_get(&proj->views, proj->curr, 0);
 	if (v == NULL)
@@ -192,11 +196,13 @@
 	view = *v;
 
 	va_start(ap, hkid);
-	argc = eng_load_args(sheet, argv, (sizeof(argv)/sizeof(argv[0])), ap, 0);
+	argc = eng_load_args(&cctx, argv, (sizeof(argv)/sizeof(argv[0])), ap, 0);
 	va_end(ap);
 	if (argc < 0)
 		return -1;
 
+	cctx.sheet = sheet;
+
 	for(n = 0; n < view->engines.used; n++) {
 		csch_view_eng_t *eng = view->engines.array[n];
 		fgw_func_t *hk = eng->hook[hkid];
@@ -203,6 +209,7 @@
 		if (hk == NULL)
 			continue;
 
+		cctx.view_eng = eng;
 		ares.type = FGW_INT;
 		ares.val.nat_int = 0;
 		argv[0].val.argv0.func = hk;
Index: trunk/src/libcschem/engine.h
===================================================================
--- trunk/src/libcschem/engine.h	(revision 777)
+++ trunk/src/libcschem/engine.h	(revision 778)
@@ -51,6 +51,11 @@
 
 };
 
+typedef struct csch_hook_call_ctx_s {
+	csch_sheet_t *sheet;
+	const csch_view_eng_t *view_eng;
+} csch_hook_call_ctx_t;
+
 csch_view_eng_t *csch_eng_alloc(csch_view_t *view, const char *user_name, const char *eng_name, const char *file_name);
 
 /* temporary until fungw C binding installation is sorted out */