How to Develop Writer Plug-ins

Wed, 02 Jul 2008 18:50:05 GMT

Catherine Heller (Channel 9) interviews Charles Teague (our Dev Lead) on Windows Live Writer.

Charles discusses the Windows Live Writer SDK which includes a managed API for extending Live Writer. He demonstrates the Polaroid Picture Plug-in and also shows how to build a "Hello World" plug-in in Visual Studio.

Charles Teague: Building Windows Live Writer Plug-ins

Changes That Affect Plug-in Developers

Wed, 29 Aug 2007 15:53:48 GMT

In an upcoming release of Windows Live Writer, we are changing the location that Windows Live Writer’s program files are installed into as well as the location of our registry settings. These changes could have an impact upon plug-in authors, though we have done our best to maintain backward compatibility. The following describes the changes in more detail and specifically discusses the impact that this will have upon existing plug-ins.

Installation Directory

In an upcoming release of Windows Live Writer, the location where Writer’s program files are installed will change. In previous betas, Writer the files would be installed to

<program files>\Windows Live Writer\

Starting in the next release, they will be installed to

<program files>\Windows Live\Writer\

Many plug-ins that are currently distributed simply install into <program files>\Windows Live Writer\plugins\. Though this isn't the most desirable installation location, we will continue to load plug-ins that are installed into <program files>\Windows Live Writer\plugins\. However, there are still cases where this change could cause problems for existing plug-ins.

1) At install time, the plug-in installer may validate that Writer is installed by looking in <program files>\Windows Live Writer\ . This validation will fail starting with the next release, and so the plug-in will not be installable. The installer should be updated to use this registry key to detect the directory in which Writer is installed into:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Live Writer\InstallDir

This value will only be present when Writer is installed (Writer un-installs the key when Writer is uninstalled).

2) At runtime, the plug-in may rely on loading assemblies or other resources based upon the application working directory. If the resource is located in <program files>\Windows Live Writer\plugins\ and the current working directory is <program files>\Windows Live\Writer\plugins\ then the resource may fail to load. Starting with Beta 2 of Windows Live Writer, plug-in authors could install their plug-ins into independent directories and register those directories with Writer, as described here (http://msdn2.microsoft.com/en-us/library/aa738841.aspx). For plug-ins with external dependencies, this is probably the best model since you will then have the freedom to create arbitrary file and directory structure without risk of collision with other installed plug-ins. If you do continue to install into the ‘plugins’ directory, it would be best if your plug-in did not depend on the working directory of the current application to resolve full paths to resources or external dependencies.

Since the above scenarios can cause install time or runtime errors, these scenarios should be addressed as soon as possible. The changes suggested above can be made immediately and will work correctly with the existing version of Windows Live Writer that is currently available as well as the upcoming release.

Registry Key Paths

In addition, the registry path where plug-ins should register themselves will also be updated from

HKEY_LOCAL_MACHINE\SOFTWARE\Windows Live Writer\PluginAssemblies
or
HKEY_CURRENT_USER\SOFTWARE\Windows Live Writer\PluginAssemblies

to

HKEY_LOCAL_MACHINE\SOFTWARE\Windows Live\Writer\PluginAssemblies
or
HKEY_CURRENT_USER\SOFTWARE\Windows Live\Writer\PluginAssemblies

We will continue to load plug-ins registered in the old registry locations, so plug-in installers should be updated to use the correct location when the opportunity presents itself. Since the old location is used by both Beta 2 and the upcoming release of Writer, plug-in developers should likely wait to make this change until the upcoming release is broadly distributed.

If you haven’t read the most recent version of the SDK documentation for Windows Live Writer, you may want to take a quick look.

Windows Live Writer SDK (http://msdn2.microsoft.com/en-us/library/aa738906.aspx )
Distributing Plug-ins (http://msdn2.microsoft.com/en-us/library/aa738841.aspx )

As always, we really appreciate the community of developers out there that are making Writer better for our users - thanks!

If you have questions or comments, please feel free to drop us a line!

-Charles Teague

Writer DevZone: SDK

How to Develop Writer Plug-ins

Changes That Affect Plug-in Developers

Installation Directory

Registry Key Paths