Developing a MySQL Workbench plugin

The MySQL Workbench tool is great for development and administration tasks. Also it's available on Windows, Linux and Mac OS X which, according to information from third party sources, is more than you can say for most of the other equivalent tools. And Workbench is free.
Having said that, most of the provided functionalities are intuitive and of daily use for developer and DBA staff alike. Moving beyond this rich out-of-the-box features set, Workbench empowers it's users to extend and develop their own custom features. For this purpose, we use both of the following:

• GRT: Generic RunTime is the internal system used by Workbench to hold model document data. It is also the mechanism by which Workbench can interact with Modules and Plugins.
• MForms: MForms is a small GUI toolkit library written for use in the MySQL Workbench project. 

MySQL Workbench is implemented with a C++ core back-end, and a native front-end for each supported platform. The custom plugins or extensions can be developed in python, using a general module structure, saved on a file named "*_grt.py".
I've developed a small proof of concept to learn how to code a custom plugin. The purpose is to provide a simple refactoring feature for the script on the SQL editor (basically it's a find and replace):
To briefly explain the code, first we import all of the workbench (wb) modules, grt and mforms:

# import the wb module
from wb import *
# import the grt module
import grt
# import the mforms module for GUI stuff
import mforms

Then we declare the module information, its name, author and version:

# define this Python module as a GRT module
ModuleInfo = DefineModule(name="Refactor", author="mjlmo", version="0.1")

@ModuleInfo.plugin("wb.text.refactor", caption = "Refactor Selection", input=[wbinputs.currentQueryBuffer()],  pluginMenu= "SQL/Utilities")
@ModuleInfo.export(grt.INT, grt.classes.db_query_QueryBuffer)

Finally, we insert the code to perform tha task in hand, in this case replace a selected text on the SQL editor with a given one on an input box. If there is no text selected, a message box will appear on screen stating that. Otherwise, we proceed with the refactoring operation.
To install this plugin, simply open MySQL Workbench, choose the "Scripting > Install Plugin/Module ..." option, browse to the "refactor_grt.py" file location and open it. Close and re-open the tool. There should be a new option on the "Tools > Utilities" menu called "Refactor Selection". Also, the plugin appear on the plugin manager:

You can read another full example regarding MySQL Workbench on how to define a module and define a plugin in Python here:
http://mysqlworkbench.org/workbench/doc/