ch01.htm

用VC开发activeX控件的电子书,很不错的

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<B>NOTE:</B> The fastest execution times are from Servers that
are in-process to the Controllers using them. But remember that
using an in-process Automation Server does not guarantee in-process
performance. If an in-process Automation Server is created in
one process space and then handed to a Controller in another process
space, the Server becomes local and suffers from the same performance
degradation as a Local Server. See Part II of this book for more
information on process spaces and their impact on Server performance.
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<H3><A NAME="Heading6">Automation Controllers</A></H3>
<P>
Automation Controllers are those applications that can use and
manipulate Automation Servers. A good example of an Automation
Controller is VB. With the VB programming language, you are able
to create, use, and destroy Automation Servers as though they
are an integral part of the language.</P>
<P>
An Automation Controller can be any type of application, DLL or
EXE, and can access the Automation Server either in-process, locally,
or remotely. Typically, the registry entries and the implementation
of the Automation Server indicate which process space the server
will execute in relation to the Controller.
<H3><A NAME="Heading7">Controls</A></H3>
<P>
ActiveX Controls are equivalent to what is referred to as OLE
Controls or OCXs. A typical Control consists of a UI representation
both at design-time and runtime, a single <TT>IDispatch</TT> interface
defining all of the methods and properties of the Control, and
a single <TT>IConnectionPoint</TT> interface for the events that
the Control can fire. In addition, the Control may have support
for persistence across its execution lifetimes and support for
various UI features, such as cut-and-paste and drag-and-drop features.
Architecturally, a Control has a large number of COM interfaces
that must be supported in order to take advantage of these features.</P>
<P>
With the release of the new OLE Control and ActiveX guidelines
for Control development, a Control is no longer limited to the
feature set defined in the preceding text. Rather, the developer
can now choose to implement only those features that are most
useful and interesting to users of the applications. The Control
and Container guidelines published by Microsoft list all the interfaces
and their specific requirements. You can find this information
at the Microsoft Web site: <A HREF="http://www.microsoft.com"><B>http://www.microsoft.com</B></A>.</P>
<P>
ActiveX Controls always execute in-process to the Container in
which they reside. The extension of a Control is typically OCX,
but in terms of execution models, it is nothing more than a standard
windows DLL.
<H3><A NAME="Heading8">COM Objects</A></H3>
<P>
COM Objects are similar in architecture to Automation Servers
and Controllers. They contain one or more COM interfaces and probably
little or no UI. These Objects, however, cannot be used by the
typical Controller application the way Automation Servers can.
The Controller must have specific knowledge of the COM interface
that it &quot;talks&quot; to in order to use the interface, which
is not the case for Automation interfaces. The Windows 95 and
NT operating systems contain hundreds of COM Objects and Custom
interfaces as extensions to the operating systems for controlling
everything from the appearance of the desktop to the rendering
of 3-D images on the screen. COM Objects are a good way to organize
a related set of functions and data, while still maintaining the
needed high-speed performance of a DLL. <BR>
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<B>NOTE:</B> Automation Servers can also benefit from COM interfaces.
These servers are known as dual-interface Servers. The <TT>IDispatch</TT>
interface of the Automation Server also has a companion COM interface
describing the methods and properties of the Object. Automation
Controllers such as VB can take advantage of these dual interfaces
to provide even greater performance when using the Server. The
one drawback to dual-interface Servers is that they are limited
to the set of data types supported by OLE Automation when defining
methods and properties. 
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<H3><A NAME="Heading9">Documents</A></H3>
<P>
ActiveX Documents, or DocObjects as they were originally called,
represent Objects that are more than a simple Control or Automation
Server. A document can be anything from a spread- sheet to a complete
invoice in an accounting application. Documents, like Controls,
have UI and are hosted by a Container application. Microsoft Word
and Excel are examples of ActiveX Document Servers, and the Microsoft
Office Binder and Microsoft Internet Explorer are examples of
ActiveX Document Containers.</P>
<P>
The ActiveX Document architecture is an extension of the OLE Linking
and Embedding model and allows the document more control over
the container in which it is being hosted. The most obvious change
is how the menus are presented. A standard OLE Document's menu
will merge with the Container, providing a combined feature set;
whereas an ActiveX Document will take over the entire menu system,
thus presenting the feature set of only the document and not that
of both the Document and the Container. The fact that the feature
set of the Document is exposed is the premise for all the differences
between ActiveX Documents and OLE Documents. The Container is
just a hosting mechanism, and the Document has all of the control.</P>
<P>
Another difference is printing and storage. An OLE Document is
intended to be a part of the Containers Document that is hosting
it and, thus, is printed and stored as a piece of the host Containers
Document. ActiveX Documents are expected to support their native
printing and storage functions and are not integrated with the
Containers Document.</P>
<P>
ActiveX Documents are used within a uniform presentation architecture,
rather than within an embedded document architecture, which is
the basis for OLE Documents. Microsoft Internet Explorer is a
perfect example of this. The Explorer merely presents the Web
pages to the user, but they are viewed, printed, and stored as
a single entity. Microsoft Word and Microsoft Excel are examples
of the OLE Document architecture. If an Excel spreadsheet is embedded
in a Word document, the spreadsheet is actually stored with the
Word document and is an integral part of it.</P>
<P>
ActiveX Documents also have the added capability of being published
as Web pages on the Internet or on a corporate intranet. Imagine
an in-house tracking system for purchase orders run from the same
Web browsers that are used to connect to the Internet.
<H3><A NAME="Heading10">Containers</A></H3>
<P>
ActiveX Containers are applications that can host Automation Servers,
Controls, and Documents. VB and the ActiveX Control Pad are examples
of Containers that can host Automation Servers and Controls. The
Microsoft Office Binder and the Microsoft Internet Explorer can
host Automation Servers, Controls, and Documents.</P>
<P>
With the decreasing requirements defined by the ActiveX Control
and Document specifications, a Container must be robust enough
to handle the cases where a Control or Document lacks certain
interfaces. Container applications may allow little or no interaction
with the Document or Control they host, or they may provide significant
interaction capabilities in both manipulation and presentation
of the hosted component. This capability, however, is dependent
upon the Container hosting the component and is not defined by
any of the Container guidelines as being required.
<H2><A NAME="Heading11">From Here...</A></H2>
<UL>
<LI><A HREF="ch02.htm">Chapter 2</A> takes a slightly more detailed
look at the specific ActiveX and OLE technologies available and
how best to apply them to your requirements.</P> 
</UL>
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<CENTER></P><FONT SIZE=1>&copy; 1997, QUE Corporation, an imprint
of Macmillan Publishing USA, a Simon and Schuster Company.</P></FONT>
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