Added support for preview the conversion

Now allows to choose how many cores to use during conversion

src/devede/preview.py

@@ -0,0 +1,46 @@
+# Copyright 2014 (C) Raster Software Vigo (Sergio Costas)
+#
+# This file is part of DeVeDe-NG
+#
+# DeVeDe-NG is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# DeVeDe-NG is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>
+
+from gi.repository import Gtk
+import os
+import devede.configuration_data
+
+class preview_window:
+
+    def __init__(self):
+
+        self.config = devede.configuration_data.configuration.get_config()
+
+    def run(self):
+
+        builder = Gtk.Builder()
+        builder.set_translation_domain(self.config.gettext_domain)
+
+        builder.add_from_file(os.path.join(self.config.glade,"wpreview.ui"))
+        builder.connect_signals(self)
+        wpreview_window = builder.get_object("dialog_preview")
+        wlength = builder.get_object("length")
+
+        wpreview_window.show_all()
+        wlength.set_value(60.0)
+        retval = wpreview_window.run()
+        self.lvalue = int(wlength.get_value())
+        wpreview_window.destroy()
+        if (retval == 1):
+            return True
+        else:
+            return False