Index: trunk/src/data.c
===================================================================
--- trunk/src/data.c	(revision 14676)
+++ trunk/src/data.c	(revision 14677)
@@ -716,4 +716,36 @@
 }
 
 
+/*** poly clip inhibit mechanism ***/
+void pcb_data_clip_inhibit_inc(pcb_data_t *data)
+{
+	int old = data->clip_inhibit;
+	data->clip_inhibit++;
 
+	if (old > data->clip_inhibit) {
+		pcb_message(PCB_MSG_ERROR, "Internal error: overflow on poly clip inhibit\n");
+		abort();
+	}
+}
+
+void pcb_data_clip_inhibit_dec(pcb_data_t *data, pcb_bool enable_progbar)
+{
+	if (data->clip_inhibit == 0) {
+		pcb_message(PCB_MSG_ERROR, "Internal error: overflow on poly clip inhibit\n");
+		assert(!"clip_inhibit underflow");
+		return;
+	}
+	data->clip_inhibit--;
+
+	pcb_data_clip_dirty(data, enable_progbar);
+}
+
+void pcb_data_clip_dirty(pcb_data_t *data, pcb_bool enable_progbar)
+{
+	if (data->clip_inhibit != 0)
+		return;
+
+	PCB_POLY_ALL_LOOP(data); {
+#warning TODO: do the clipping here
+	} PCB_ENDALL_LOOP;
+}
Index: trunk/src/data.h
===================================================================
--- trunk/src/data.h	(revision 14676)
+++ trunk/src/data.h	(revision 14677)
@@ -63,6 +63,9 @@
 /**/
 	pcb_parenttype_t parent_type;
 	pcb_parent_t parent;
+
+/* poly clip inhibit */
+	int clip_inhibit; /* counter: >0 means we are in inhibit mode */
 };
 
 #define pcb_max_group(pcb) ((pcb)->LayerGroups.len)
@@ -184,4 +187,20 @@
 #define PCB_REAL_DATA(pcb) \
 	((pcb)->is_footprint ? (pcb_subclist_first(&(pcb)->Data->subc)->data) : ((pcb)->Data))
 
+
+/*** Polygon clipping inhibit ***/
+
+/* increase the inhibit counter (stop clipping polygons) */
+void pcb_data_clip_inhibit_inc(pcb_data_t *data);
+
+/* decrease the inhibit counter - if it's zero, reclip all dirty polygons;
+   enable_progbar controls whether a progress bar is drawn for reclips
+   that take longer than a few seconds. */
+void pcb_data_clip_inhibit_dec(pcb_data_t *data, pcb_bool enable_progbar);
+
+/* attempt to reclip all dirty polygons; normally called by
+   pcb_data_clip_inhibit_dec(). */
+void pcb_data_clip_dirty(pcb_data_t *data, pcb_bool enable_progbar);
+
+
 #endif