Python Gtk widgets support

## Python Gtk widgets support Add python support to your catalog — How to write and install a catalog for a python widget library |

## Introduction

Glade supports loading widgets coded in python by linking and running the python interpreter from the gladepython catalog plugin.

So in order for glade to include your python gtk widgets you will have to:

  a) specify gladepython support code as your plugin library.
  b) set glade_python_init as you init function.
  c) make sure your catalog name is the same as your python import library since `glade_python_init()` will use this name to import your widgets into the interpreter.

    <glade-catalog name="pythonplugin" library="gladepython"
    domain="glade-3" depends="gtk+">
     <init-function>glade_python_init</init-function>

     <glade-widget-classes>
       <glade-widget-class title="MyBox" name="MyBox" generic-name="mybox"/>
     </glade-widget-classes>

     <glade-widget-group name="python" title="Python">
       <glade-widget-class-ref name="MyBox"/>
     </glade-widget-group>
    </glade-catalog>

Glade's python interpreter will look up for your widgets in the same places it looks for regular catalogs plugins, that is $GLADE_ENV_CATALOG_PATH enviroment variable and `pkg-config --variable=catalogdir gladeui-1.0` So the easiest thing would be to make a symlink in one of those directory, just do not forget that the name should be the one specified in your catalog name.

pythonplugin.py

    import gobject
    import gtk

    class MyBox(gtk.HBox):
           __gtype_name__ = 'MyBox'

           def __init__(self):
                   gtk.HBox.__init__(self)