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

5.1 Program Architecture IMPLEMENTATION
The interface to PowerPoint is complemented by the CPPTShape class. There
is an instance of this class for each shape – rectangle, arrow, text box and the like –
in a PowerPoint document. The methods of this class provide ways to add, modify
and displace PowerPoint shapes.
While each document window contains precisely one presentation, the same
presentation may be opened in multiple document windows simultaneously. Hence,
presentations are represented independently from document windows by the class
CPresentation. Presentation objects contain static or user specified information
about a PowerPoint document. Each presentation consists of a number of slides,
which in our data model are represented by instances of CSmartGrid. The smart
grid is the link between a presentation and its smart elements. Because a document
window can edit one slide at a time, each instance of CPPTDocWnd needs only
a single reference to the smart grid that is currently visible.
A priori, each slide has a smart grid and a container, which is an instance
of CContainerSE. The container spans the entire slide and holds gridlines to
represent the positions and spatial relations of its contained smart elements. The
container itself is invisible to the user and indifferent against user action.
Gridlines, being represented by CGridLine objects, are partitioned by their
orientation – vertical and horizontal – and held by one of two CGridLineGroup
objects per container. Each group of gridlines always contains at least two gridlines,
which indicate the lower and upper bounds of their container in the respective
dimension.
Smart elements – i. e., instances of CSmartElement – are placed relative to a
slide’s container, their location being determined by the gridlines they are bound to.
Each smart element represents a self-contained composition of arbitrary complexity
that is placed and sized in its entirety. Each smart element is made up of one
or more features, which in the case of a chart correspond to columns and labels
and are represented by the class CFeature. Features usually have user specified
options, but cannot be moved or resized independently from their smart element.
A feature, in turn, usually consists of one or more PowerPoint shapes. However,
certain features serve only mediating purposes in the user interface and do not have
a corresponding PowerPoint shape.
In fact, the objects which I call features are essential for the user interface. On
request, a feature generates a number of instances of CUIObject – handles or
menu items, for example – that provide means for the user to modify the feature
(cf. Sect. 5.1.3). All UI objects of all currently visible features are registered with
the document window and receive messages therefrom. The visual representation
of a UI object involves mapping texture coordinates to screen coordinates and is
implemented in the class CVisualElement.
This same pattern applies to the user interface representation for gridlines. To be
visible and user-modifiable, CGridLine objects generate instances of CUIGridLine
and CGridLineHotDragHandle. Indeed, these latter classes are subclasses of
CUIObject (cf. Fig. 38(a)) and as such also own visual elements and are message-
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