Figuring Out This Shell Game

This book is clearly for advanced shell programmers only.

• By Paul G. Brown
• 03/01/2001

When you fly an airplane you learn one fact quickly - you're judged by the quality of your landing. No matter how perfect the flight, one little bump on landing will often lower your passenger's perception of your skills.

Application development suffers from the same fate in that we're often judged by the feature from another application that is missing in ours. Until now, the realm of the Windows shell was reserved for the hardcore C++ developer with time to wade through the limited documentation available.

Visual Basic Shell Programming from O'Reilly & Associates gathers all the required knowledge and presents it in a concise and focused manner that will have you integrating these features fairly quickly. The book presents ways to make your application behave in a Windows standard manner using the same techniques and calls as the Microsoft folks.

The term feature in this context is really describing extensions to the Windows shell. In other words, ways of making it do more than was originally programmed but in a manner that is consistent with the way other features are implemented. One of the key tools is a handler, an object that performs an action when an event occurs. This can be a right-click, double-click or deletion. The main idea is to make Windows behave the way you want. Let's start with a handler that we see in action all the time.

Icon Handlers allow the developer to change a desktop icon based on a specified criteria. Say you had a module of your application that allowed the manager to approve purchase orders. You could place a link on the desktop for starting that module. For an icon you use an empty inbox tray. When there are purchase orders that need approval, the tray can appear full. Now, the manager simply looks at the icon and knows if they need to approve anything. Sound familiar? It should, it's the same as the Recycle Bin. This is one of the many tricks available and is called an Icon Handler.

Other handlers include InfoTip, which controls the ToolTip text displayed in Explorer for a file. A CopyHook can prevent the copying or deletion of a file or printer. How about custom drag-and-drop handling in Explorer - Data Handlers. Expose data in Windows Explorer as if it were folders and directories using Windows Namespace Extensions. All of these options allow you to customize the user's environment, improving their experience. Application developers will find their users are more satisfied because their custom client tracking system behaves exactly the way they expect. Network administrators will find that they get fewer support calls for the same reason - things do what the user expects. Because we're extending the Windows, rather than coding everything ourselves, the cost of implementing these features can be very low.

Before you rush out and buy this book, be aware that it's not targeted at beginners. The book assumes you're a proficient programmer and will be able to understand the topics presented. In the preface, the author states that audience is for developers who have done just a few projects. This may be rather optimistic but the required information is there for the taking; the reader just needs to spend sometime working with the tools. At a minimum you should have a solid understanding of event handling with some exposure to the Windows Registry and C.

My only real complaint with the book was the binding. I hadn't opened it twice and the spine was loose. While this makes it lay flat I can see this being a frequently used volume where you don't want to lose any pages. There should also be something on the back that identifies it as an advanced concepts book. The only real comment is a quote that recommends everyone from novice to expert that is misleading.

Nonetheless, if you're a developer looking to take the next step with your apps then this is the book for you.