Index: trunk/src/plug_io.c
===================================================================
--- trunk/src/plug_io.c	(revision 2641)
+++ trunk/src/plug_io.c	(revision 2642)
@@ -148,35 +148,52 @@
 	return f1->prio > f2->prio;
 }
 
-/* Find the plugin that offers the highest write prio for the format */
-static plug_io_t *find_writer(plug_iot_t typ, const char *fmt)
+/* Find all plugins that can handle typ/wr and build an ordered list in available[], 
+   highest prio first. If fmt is NULL, use the default fmt for each plugin.
+   Return the length of the array. */
+static int find_io(find_t *available, int avail_len, plug_iot_t typ, const char *fmt)
 {
-	find_t available[32]; /* wish we had more than 32 IO plugins... */
 	int len = 0;
 
-	if (fmt == NULL) {
-#warning TODO: rather save format information on load
-		fmt = "pcb";
-	}
 
 #define cb_append(pl, pr) \
 	do { \
 		if (pr > 0) { \
-			assert(len < sizeof(available)/sizeof(available[0])); \
+			assert(len < avail_len ); \
 			available[len].plug = pl; \
 			available[len++].prio = pr; \
 		} \
 	} while(0)
 
-	HOOK_CALL_ALL(plug_io_t, plug_io_chain, fmt_support_prio, cb_append, typ, 1, fmt);
+	HOOK_CALL_ALL(plug_io_t, plug_io_chain, fmt_support_prio, cb_append, typ, 1, (fmt == NULL ? __ch__->default_fmt : fmt));
+
+	if (len > 0)
+		qsort(available, len, sizeof(available[0]), find_prio_cmp);
+#undef cb_append
+
+	return len;
+}
+
+/* Find the plugin that offers the highest write prio for the format */
+static plug_io_t *find_writer(plug_iot_t typ, const char *fmt)
+{
+	find_t available[PCB_IO_MAX_FORMATS];
+	int len;
+
+	if (fmt == NULL) {
+#warning TODO: rather save format information on load
+		fmt = "pcb";
+	}
+
+	len = find_io(available, sizeof(available)/sizeof(available[0]), typ, fmt);
+
 	if (len == 0)
 		return NULL;
 
-	qsort(available, len, sizeof(available[0]), find_prio_cmp);
 	return available[0].plug;
-#undef cb_append
 }
 
+
 int WriteBuffer(FILE *f, BufferType *buff, const char *fmt)
 {
 	int res;
@@ -781,3 +798,38 @@
 	return (fclose(fp) ? STATUS_ERROR : result);
 }
 
+
+int pcb_io_list(pcb_io_formats_t *out, plug_iot_t typ, int wr, int do_digest)
+{
+	find_t available[PCB_IO_MAX_FORMATS];
+	int n;
+
+	memset(out, 0, sizeof(pcb_io_formats_t));
+	out->len = find_io(available, sizeof(available)/sizeof(available[0]), typ, NULL);
+
+	if (out->len == 0) 
+		return 0;
+
+	for(n = 0; n < out->len; n++)
+		out->plug[n] = available[n].plug;
+
+	if (do_digest) {
+		for(n = 0; n < out->len; n++)
+			out->digest[n] = pcb_strdup_printf("%s (%s)", out->plug[n]->default_fmt, out->plug[n]->description);
+		out->digest[n] = NULL;
+	}
+	return out->len;
+}
+
+void pcb_io_list_free(pcb_io_formats_t *out)
+{
+	int n;
+
+	for(n = 0; n < out->len; n++) {
+		if (out->digest[n] != NULL) {
+			free(out->digest[n]);
+			out->digest[n] = NULL;
+		}
+	}
+}
+
Index: trunk/src/plug_io.h
===================================================================
--- trunk/src/plug_io.h	(revision 2641)
+++ trunk/src/plug_io.h	(revision 2642)
@@ -31,7 +31,7 @@
 #include "global.h"
 #include "conf.h"
 
-typedef enum {
+typedef enum { /* I/O type bitmask; each bit is one thing to save or load, not all formats support all things */
 	PCB_IOT_PCB        = 1,
 	PCB_IOT_FOOTPRINT  = 2,
 	PCB_IOT_FONT       = 4,
@@ -111,4 +111,23 @@
 void RemoveTMPData(void);
 #endif
 
+/********** helpers **********/
+
+/* wish we had more than 32 IO plugins... */
+#define PCB_IO_MAX_FORMATS 32
+
+/* A list of format plugins available for a given purpose */
+typedef struct {
+	int len;
+	const plug_io_t *plug[PCB_IO_MAX_FORMATS+1];
+	char *digest[PCB_IO_MAX_FORMATS+1];           /* string that contains the format identifier and the description */
+} pcb_io_formats_t;
+
+/* Search all io plugins to see if typ/wr is supported. Return an ordered
+   list in out. If do_digest is non-zero, fill in the digest field. Returns
+   number of suitable io plugins. Call pcb_io_list_free() on out when it is not
+   needed anymore. */
+int pcb_io_list(pcb_io_formats_t *out, plug_iot_t typ, int wr, int do_digest);
+void pcb_io_list_free(pcb_io_formats_t *out);
+
 #endif