[dia] [warningectomy] implicit declaration of function 'filter_unregister_callback'

[Hans Breuer <hans src gnome org>]

commit ce0b3223b9b4438d72fa4bf589938096a1fbdab2
Author: Hans Breuer <hans breuer org>
Date:   Sat May 4 14:44:26 2013 +0200

    [warningectomy] implicit declaration of function 'filter_unregister_callback'
    
    The non-win32 build was referencing a function not implemented at all.
    It could not be called, due to being protected by plugin_can_unload(),
    but that was just coincidence.
    Now filter_unregister_callback() is defined and implemented, including
    some error handling for callback's being invoked after unloading of
    the providing plug-in.

 app/menus.c               |    6 ++++++
 lib/filter.c              |   14 ++++++++++++++
 lib/filter.h              |    1 +
 lib/libdia.def            |    1 +
 plug-ins/cairo/diacairo.c |    4 ++--
 5 files changed, 24 insertions(+), 2 deletions(-)
---
diff --git a/app/menus.c b/app/menus.c
index 1de172d..be00f27 100644
--- a/app/menus.c
+++ b/app/menus.c
@@ -1249,6 +1249,11 @@ plugin_callback (GtkWidget *widget, gpointer data)
 {
   DiaCallbackFilter *cbf = data;
 
+  /* check if the callback filter is still available */
+  if (!g_list_find (filter_get_callbacks (), cbf)) {
+    message_error (_("The function is not available anymore."));
+    return;
+  }
   /* and finally invoke it */
   if (cbf->callback) {
     DDisplay *ddisp = NULL;
@@ -1280,3 +1285,4 @@ plugin_callback (GtkWidget *widget, gpointer data)
     }
   }
 }
+
diff --git a/lib/filter.c b/lib/filter.c
index 63c84e2..fc6644e 100644
--- a/lib/filter.c
+++ b/lib/filter.c
@@ -304,9 +304,23 @@ filter_register_callback(DiaCallbackFilter *cbfilter)
   callback_filters = g_list_append (callback_filters, (gpointer)cbfilter);
 }
 
+void
+filter_unregister_callback(DiaCallbackFilter *cbfilter)
+{
+  /* Unregistering a callback filter should remove it from the menu, too.
+   * But that would involve quite some additional code, maybe some
+   * notification to update menus ...
+   * We take the easy approach to let the caller check if the callback
+   * is still valid, i.e. the filter still exists.
+   */
+  callback_filters = g_list_remove (callback_filters, cbfilter);
+}
+
+
 /* return the registered callbacks list, called once to build menus */
 GList *
 filter_get_callbacks(void)
 {
   return g_list_first (callback_filters);
 }
+
diff --git a/lib/filter.h b/lib/filter.h
index 107c657..1c80c7f 100644
--- a/lib/filter.h
+++ b/lib/filter.h
@@ -125,6 +125,7 @@ DiaImportFilter *filter_guess_import_filter(const gchar *filename);
 DiaImportFilter *filter_import_get_by_name(const gchar *name);
 
 void filter_register_callback(DiaCallbackFilter *cbfilter);
+void filter_unregister_callback(DiaCallbackFilter *cbfilter);
 /* returns all registered callbacks */
 GList *filter_get_callbacks(void);
 
diff --git a/lib/libdia.def b/lib/libdia.def
index 44be57c..a903c10 100644
--- a/lib/libdia.def
+++ b/lib/libdia.def
@@ -440,6 +440,7 @@ EXPORTS
  filter_register_callback
  filter_register_export
  filter_register_import
+ filter_unregister_callback
  filter_unregister_export
  filter_unregister_import
 
diff --git a/plug-ins/cairo/diacairo.c b/plug-ins/cairo/diacairo.c
index 6cb87b5..ef5ac10 100644
--- a/plug-ins/cairo/diacairo.c
+++ b/plug-ins/cairo/diacairo.c
@@ -523,9 +523,9 @@ _plugin_unload (PluginInfo *info)
 #if DIA_CAIRO_CAN_EMF
   filter_unregister_export(&emf_export_filter);
   filter_unregister_export(&wmf_export_filter);
-  /* filter_unregister_callback (&cb_clipboard); */
+  filter_unregister_callback (&cb_clipboard);
 #endif
-  /* filter_unregister_callback (&cb_gtk_print); */
+  filter_unregister_callback (&cb_gtk_print);
 }
 
 /* --- dia plug-in interface --- */