Plug-in Development for Google Desktop

Getting Started

Things you need

• .Net Framework 1.1
• Visual Studio .Net
• Google Desktop SDK

How to get started

You need to create a COM object.

What is a COM object and why do I need to create it?

GD uses COM objects as plugins. Actually these are like ActiveX components. They are meant to be reusable.

How to create a COM object

In Visual Studio, create a C# Class Library.

Preliminary code for the Class Library project

You should implement two (2) methods:

static void ComRegisterFunctionAttribute(Type t) {
include initialization code here
}

This function is called whenever you register your COM object to the system. You can put initialization code here, like code that will register our plugin to GD (Details later).

static void ComUnregisterFunctionAttribute(Type t) {
}

This function is called whenever you unregister your COM object.

You should have the following statement:

using System.Runtime.InteropServices;

What kind of files are created when I compile my Class Library project?

After building your Class Library project, Visual Studio will generate the following file types in your output folder: .dll and .tlb

The .dll file generated is actually a COM object that we need to register to the system.

How to load/register a COM object

Use: regasm [dllfile] /tlb

Regasm.exe is located in your .Net Framework bin folder.

What method/code is first executed after I load a COM object?

The system makes a call to ComRegisterFunctionAttribute so it is necessary that you implement this method. It is here where we put our initialization, like a block of code that will register our plugin to GD.

Registering the plugin to GD

try {
GoogleDesktopRegistrarClass registrar = new GoogleDesktopRegistrarClass();
// Start component registration by specifying our attributes
object[] descriptions = {
"Title", pluginName,
"Description", pluginName,
"Icon", ""
};

registrar.StartComponentRegistration(controlGuid, descriptions);

IGoogleDesktopRegisterDisplayPlugin displayRegistration = 
(IGoogleDesktopRegisterDisplayPlugin)

registrar.GetRegistrationInterface("GoogleDesktop.DisplayPluginRegistration");

displayRegistration.RegisterPlugin(controlGuid, false);
// Done with component registration.
registrar.FinishComponentRegistration();
}
catch (Exception e) {
MessageBox.Show("Exception thrown during registration. Description=" + e.Message);
}

What happens when my plugin is registered in GD?

Your plugin will appear in the add/remove panel list in Google Desktop.