Bug 796896 - Button to complete an export not intuitively placed or discoverable

The assistant file page is made up of an embedded GtkFileChooser widget
and associated OK button which seems out of place. Remove the OK button
and use the selection-changed signal to control the 'Forward' button.

gnucash/import-export/csv-exp/assistant-csv-export.c

@@ -73,7 +73,7 @@ void csv_export_show_range_cb (GtkRadioButton *button, gpointer user_data);
 void csv_export_start_date_cb (GtkWidget *radio, gpointer user_data);
 void csv_export_end_date_cb (GtkWidget *radio, gpointer user_data);
 
-void csv_export_file_chooser_confirm_cb (GtkWidget *button, CsvExportInfo *info);
+void csv_export_file_chooser_selection_changed_cb (GtkFileChooser *chooser, CsvExportInfo *info);
 
 static const gchar *finish_tree_string = N_(
             /* Translators: %s is the file name string. */
@@ -121,55 +121,43 @@ static const gchar *start_trans_simple_string = N_(
 
 
 /**************************************************
- * csv_export_file_chooser_confirm_cb
+ * csv_export_file_chooser_selection_changed_cb
  *
- * call back for ok button in file chooser widget
+ * call back for GtkFileChooser widget
  **************************************************/
 void
-csv_export_file_chooser_confirm_cb (GtkWidget *button, CsvExportInfo *info)
+csv_export_file_chooser_selection_changed_cb (GtkFileChooser *chooser, CsvExportInfo *info)
 {
     GtkAssistant *assistant = GTK_ASSISTANT(info->window);
     gint num = gtk_assistant_get_current_page (assistant);
     GtkWidget *page = gtk_assistant_get_nth_page (assistant, num);
-
     gchar *file_name;
 
     gtk_assistant_set_page_complete (assistant, page, FALSE);
 
     file_name = gtk_file_chooser_get_filename (GTK_FILE_CHOOSER(info->file_chooser));
 
-    if (file_name)
+    /* Test for a valid filename and not a directory */
+    if (file_name && !g_file_test (file_name, G_FILE_TEST_IS_DIR))
     {
-        if (g_file_test (file_name, G_FILE_TEST_EXISTS))
-        {
-            const char *format = _("The file %s already exists. "
-                                   "Are you sure you want to overwrite it?");
-
-            /* if user says cancel, we should break out */
-            if (!gnc_verify_dialog (GTK_WINDOW (assistant), FALSE, format, file_name))
-                return;
-        }
+        gchar *filepath = gnc_uri_get_path (file_name);
+        gchar *filedir = g_path_get_dirname (filepath);
 
+        g_free (info->file_name);
         info->file_name = g_strdup (file_name);
-        gtk_assistant_set_page_complete (assistant, page, TRUE);
-    }
 
-    if (file_name)
-    {
-        gchar *filepath = gnc_uri_get_path (file_name);
-        gchar *filedir = g_path_get_dirname (filepath);
+        g_free (info->starting_dir);
         info->starting_dir = g_strdup (filedir);
+
         g_free (filedir);
         g_free (filepath);
+
+        gtk_assistant_set_page_complete (assistant, page, TRUE);
     }
     g_free (file_name);
 
     DEBUG("file_name selected is %s", info->file_name);
     DEBUG("starting directory is %s", info->starting_dir);
-
-    /* Step to next page if page is complete */
-    if(gtk_assistant_get_page_complete (assistant, page))
-        gtk_assistant_set_current_page (assistant, num + 1);
 }
 
 
@@ -268,7 +256,6 @@ csv_export_custom_entry_cb (GtkWidget *widget, gpointer user_data)
     info->separator_str = strdup (custom_str);
 
     if (info->use_custom == TRUE && gtk_entry_get_text_length (GTK_ENTRY(info->custom_entry)) == 0)
-
         gtk_assistant_set_page_complete (assistant, page, FALSE);
     else
         gtk_assistant_set_page_complete (assistant, page, TRUE);
@@ -701,6 +688,16 @@ csv_export_assistant_finish_page_prepare (GtkAssistant *assistant,
     gtk_label_set_text (GTK_LABEL(info->finish_label), text);
     g_free (text);
 
+    /* Test if the filename exists */
+    if (g_file_test (info->file_name, G_FILE_TEST_EXISTS))
+    {
+        const char *format = _("The file %s already exists. "
+                               "Are you sure you want to overwrite it?");
+
+        /* if user says cancel, we should go back a page */
+        if (!gnc_verify_dialog (GTK_WINDOW (assistant), FALSE, format, info->file_name))
+            gtk_assistant_previous_page (assistant);
+    }
     /* Enable the Assistant Buttons */
     gtk_assistant_set_page_complete (assistant, page, TRUE);
 }
@@ -921,15 +918,9 @@ csv_export_assistant_create (CsvExportInfo *info)
     /* File chooser Page */
     info->file_page = GTK_WIDGET(gtk_builder_get_object(builder, "file_page"));
     info->file_chooser = gtk_file_chooser_widget_new (GTK_FILE_CHOOSER_ACTION_SAVE);
-    button = gtk_button_new_with_mnemonic (_("_OK"));
-    gtk_widget_set_size_request (button, 100, -1);
-    gtk_widget_show (button);
-    h_box = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 0);
-    gtk_box_set_homogeneous (GTK_BOX (h_box), TRUE);
-    gtk_box_pack_start(GTK_BOX(h_box), button, FALSE, FALSE, 0);
-    gtk_file_chooser_set_extra_widget (GTK_FILE_CHOOSER(info->file_chooser), h_box);
-    g_signal_connect (G_OBJECT(button), "clicked",
-                      G_CALLBACK(csv_export_file_chooser_confirm_cb), info);
+
+    g_signal_connect (G_OBJECT(info->file_chooser), "selection-changed",
+                      G_CALLBACK(csv_export_file_chooser_selection_changed_cb), info);
 
     box = GTK_WIDGET(gtk_builder_get_object (builder, "file_page"));
     gtk_box_pack_start (GTK_BOX (box), info->file_chooser, TRUE, TRUE, 6);