Professional Microsoft® SharePoint® Designer 2007

14.1. What Is the Web Part Page Services Component?

A SharePoint Web Part Page is a complicated beast. It must support the loading and display of components from a variety of sources. In addition, it must be able to adapt to the changes as users add and remove Web Parts (and connections between them) at run time. Coordinating all of this is the job of the Web Part Page Services Component (WPSC).

In code, the component's object ID is WPSC. The rest of this chapter uses WPSC for all references to the component in the text as well.

The functions of the WPSC fall into two general categories:

• Page initialization

• Page services

14.1.1. Page Initialization

SharePoint detects which browser is being used, and takes slightly different actions based on what it finds. A variety of JavaScript objects, typically including the WPSC, are instantiated at run time by including the file IE50UP.JS, IE55UP.JS, or NON_IE.JS, depending upon what functions the user's browser supports.

As implied by their titles, IE55UP.JS is used for IE 5.5 or higher browsers, while IE50UP.JS is used for down-level versions of IE, and NON_IE.JS is for other browsers. This allows calls made to the WPSC to degrade gracefully on older versions of Internet Explorer. The WPSC is not implemented in NONIE.JS. As always, test your code on multiple browsers.

As a Web Part Page loads, the WPSC receives information about the Web Parts on the page, and performs various housekeeping tasks. Among other things, the WPSC is responsible ...