Internet Explorer uses Microsoft ActiveX Controls and Active Document interfaces to connect components. IExplore.exe is at the top level; it is a small application that is instantiated when Internet Explorer is loaded. This executable application uses Internet Explorer components to perform the navigation, history maintenance, favorites maintenance, HTML parsing and rendering, and so on, while it supplies the toolbar and frame for the stand-alone browser. IExplorer.exe directly hosts the Shdocvw.dll component. Shdocvw.dll in turn hosts the Mshtml.dll component, as well as any other Active Document component (such as a Microsoft Office application) that can be loaded in place in the browser when the user navigates to a specific document type. Shdocvw.dll supplies the functionality associated with navigation, in-place linking, favorites and history management, and PICS support. This dynamic-link library (DLL) also exposes interfaces to its host to allow it to be hosted separately as an ActiveX control. The Shdocvw.dll component is more frequently referred to as the WebBrowser Control. In-place linking refers to the ability to click a link in the HTML of the loaded document and to load a new HTML document in the same instance of the WebBrowser Control. If only Mshtml.dll is being hosted, a click on the link results in a new instance of the browser. Mshtml.dll is the component that performs the HTML parsing and rendering in Internet Explorer 4.0 and later, and it also exposes the HTML document through the Dynamic HTML Object Model. This component hosts the scripting engines, Microsoft virtual machine, ActiveX Controls, plug-ins, and other objects that might be referenced in the loaded HTML document. Mshtml.dll implements the Active Document server interfaces, which allows it to be hosted using standard Component Object Model (COM) interfaces. The WebBrowser Control provides a rich set of functionality that a host typically requires, such as that for in-place linking. Therefore, it is much more applicable for most applications to host this control instead of MSHTML for browsing or viewing HTML documents. Hosting MSHTML is recommended only for specialized applications, such as parsing HTML. The WalkAll Sample Source Page demonstrates how to host MSHTML. It should also be noted that although hosting MSHTML is slightly more lightweight than hosting the WebBrowser Control, the savings rarely justify the extra work involved in implementing functionality that is already available in the WebBrowser Control. It is very likely that the WebBrowser Control will already be loaded in memory, and navigating to a frameset page will also result in the WebBrowser Control being loaded as part of the standard working set. Excerpted from the MSDN Library article About the Browser. 2005 Microsoft Corporation. |