think-cell technical report TC2003/01 A GUI-based Interaction ...

5 Implementation
IMPLEMENTATION
The prototype that was developed in the course of this work is based on a product
by think-cell Software. The think-cell product is an add-in to Microsoft PowerPoint
that uses a variety of techniques to interact with PowerPoint (Fig. 36). The Micro-
soft Office Object Model and the Active Document Interface, which are designed
for add-ins like the think-cell product, allow only limited access to the PowerPoint
engine. Therefore, in the think-cell implementation, these techniques are supple-
mented by Window Subclassing for message interception. Moreover, think-cell uses
DirectX to create custom on-screen UI widgets.
My implementation does not make immediate use of any of the techniques men-
tioned. The classes that I implemented merely interact with the high-level C++
programming interface of the think-cell product and are compiled as part of that
product.
User Interface
think-cell Add-In
PowerPoint
Excel
Win 32 API
DirectX
Object Model Active Document Interface Active Document Interface Office Object Model SubclassingOffice Window
Figure 36: The think-cell architecture uses a variety of techniques to interact with
PowerPoint.
5.1 Program Architecture
To get an understanding of the program architecture in general and the user inter-
face code in particular, in this section a number of structural diagrams are discussed
in turn. I begin with an overview of the major entities and relations, followed by
a close-up look at a hierarchy of UI-related subclasses and finally I examine some
interaction scenarios involving a couple of classes.
5.1.1 Overview: Entity-Relation
Figure 37 provides an overview of the most important inter-class relationships of the
C++ code. The CPPTFrame class relates to a runtime instance of PowerPoint. It
contains presentations and document windows. PowerPoint is an MDI 11 application
and each instance of CPPTDocWnd relates to a runtime document window. Both
classes intercept Windows messages, most prominently repaint requests and user
input like mouse movements and key presses. They process and forward those
messages at application or window level, respectively.
11 Multiple Document Interface (MDI): A single running application instance can open and edit
multiple independent documents at a time.
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