+reference_manual (GtkMenuItem *menu, gpointer data)
+{
+ GError *err = NULL;
+ gchar *cmd = g_strdup_printf ("yelp file://%s", relocate (DOCDIR "/pspp.xml"));
+
+ if ( ! g_spawn_command_line_async (cmd, &err) )
+ {
+ msg (ME, _("Cannot open reference manual: %s"), err->message);
+ }
+
+ g_free (cmd);
+ g_clear_error (&err);
+}
+
+
+extern struct dataset *the_dataset;
+extern struct source_stream *the_source_stream;
+extern PsppireDataStore *the_data_store;
+
+/* Lazy casereader callback function used by execute_syntax. */
+static struct casereader *
+create_casereader_from_data_store (void *data_store_)
+{
+ PsppireDataStore *data_store = data_store_;
+ return psppire_data_store_get_reader (data_store);
+}
+
+gboolean
+execute_syntax (struct getl_interface *sss)
+{
+ struct lexer *lexer;
+ gboolean retval = TRUE;
+
+ struct casereader *reader;
+ size_t value_cnt;
+ casenumber case_cnt;
+ unsigned long int lazy_serial;
+
+ /* When the user executes a number of snippets of syntax in a
+ row, none of which read from the active file, the GUI becomes
+ progressively less responsive. The reason is that each syntax
+ execution encapsulates the active file data in another
+ datasheet layer. The cumulative effect of having a number of
+ layers of datasheets wastes time and space.
+
+ To solve the problem, we use a "lazy casereader", a wrapper
+ around the casereader obtained from the data store, that
+ only actually instantiates that casereader when it is
+ needed. If the data store casereader is never needed, then
+ it is reused the next time syntax is run, without wrapping
+ it in another layer. */
+ value_cnt = psppire_data_store_get_value_count (the_data_store);
+ case_cnt = psppire_data_store_get_case_count (the_data_store);
+ reader = lazy_casereader_create (value_cnt, case_cnt,
+ create_casereader_from_data_store,
+ the_data_store, &lazy_serial);
+ proc_set_active_file_data (the_dataset, reader);
+
+ g_return_val_if_fail (proc_has_active_file (the_dataset), FALSE);
+
+ lexer = lex_create (the_source_stream);
+
+ getl_append_source (the_source_stream, sss, GETL_BATCH, ERRMODE_CONTINUE);
+
+ for (;;)
+ {
+ enum cmd_result result = cmd_parse (lexer, the_dataset);
+
+ if ( cmd_result_is_failure (result))
+ {
+ retval = FALSE;
+ if ( source_stream_current_error_mode (the_source_stream)
+ == ERRMODE_STOP )
+ break;
+ }
+
+ if ( result == CMD_EOF || result == CMD_FINISH)
+ break;
+ }
+
+ getl_abort_noninteractive (the_source_stream);
+
+ lex_destroy (lexer);
+
+ psppire_dict_replace_dictionary (the_data_store->dict,
+ dataset_dict (the_dataset));
+
+ reader = proc_extract_active_file_data (the_dataset);
+ if (!lazy_casereader_destroy (reader, lazy_serial))
+ psppire_data_store_set_reader (the_data_store, reader);
+
+ som_flush ();
+
+ psppire_output_window_reload ();
+
+ return retval;
+}
+
+
+
+/* Create a deep copy of SRC */
+GtkListStore *
+clone_list_store (const GtkListStore *src)