Add filter for currency symbol for GNCAmountEdit widget

When pasting an amount that includes the currency symbol the validation
will silently fail which may lead to unusual behaviour.

libgnucash/app-utils/gnc-ui-util.c

@@ -2784,3 +2784,28 @@ gnc_filter_text_for_currency_symbol (const gchar *incoming_text,
     g_strfreev (split);
     return ret_text;
 }
+
+gchar *
+gnc_filter_text_for_currency_commodity (const gnc_commodity *comm,
+                                        const gchar *incoming_text,
+                                        const gchar **symbol)
+{
+    if (!incoming_text)
+    {
+        *symbol = NULL;
+        return NULL;
+    }
+
+    if (!gnc_commodity_is_currency (comm))
+    {
+        *symbol = NULL;
+        return g_strdup (incoming_text);
+    }
+
+    if (comm)
+        *symbol = gnc_commodity_get_nice_symbol (comm);
+    else
+        *symbol = gnc_commodity_get_nice_symbol (gnc_default_currency ());
+
+    return gnc_filter_text_for_currency_symbol (incoming_text, *symbol);
+}

libgnucash/app-utils/gnc-ui-util.h

@@ -433,6 +433,20 @@ void gnc_filter_text_set_cursor_position (const gchar *incoming_text,
 gchar * gnc_filter_text_for_currency_symbol (const gchar *incoming_text,
                                              const gchar *symbol);
 
+/** Returns the incoming text removed of currency symbol
+ * 
+ * @param comm commodity of entry if known
+ * 
+ * @param incoming_text The text to filter
+ *
+ * @param symbol return the symbol used
+ *
+ * @return The incoming text with symbol removed to be freed by the caller
+*/
+gchar * gnc_filter_text_for_currency_commodity (const gnc_commodity *comm,
+                                                const gchar *incoming_text,
+                                                const gchar **symbol);
+
 #endif
 /** @} */
 /** @} */