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

4.3 Specifying the User Interface INTERACTION CONCEPT
1. In addition to Power-
Point AutoShapes, “smart elements”
can be inserted from the
think-cell menu.
Single-Click Insertion
2a. In insertion mode,
when the mouse cursor is moved, the
software proposes reasonable placements
for the new element.
2b. Alternatively, an arbitrary
area can be selected by drag-and-drop.
Borders are snapped to existing gridlines,
if close enough.
Figure 16: Inserting a new shape into the smart grid
3. New gridlines are
generated, if required.
4. Layout optimization:
Shapes are sized appropriately,
the layout is centered, etc.
The single-click insertion is strictly optimized to make the common case fast. The
idea is to detect common cases based on the mouse pointer position and existing
shapes on the slide. The most typical insertion location that is detected by my
software is shown to the user by a transparent rectangle that serves as a placeholder
for the new element. If the user is satisfied with the system’s proposition, a single
click suffices to insert the new element.
This concept is enabled by the smart grid and the solver. In plain PowerPoint,
it would be pointless to suggest one pixel position or another. However, with the
solver taking care of the details, the space of distinct solutions for placement is
drastically reduced: Each edge of the new element’s bounding box can either be
bound to an existing gridline, or it creates a new gridline between two existing ones.
As long as all edges that share the same position are bound to the same gridline and
the total order of gridlines is preserved, the absolute placement in terms of pixels
does not make a difference. The solver would fix it, anyway.
Figures 17 through 20 show the effect of some heuristics that propose common
placements. All figures are live screenshots from my prototypical implementation
that is presented in chapter 5.
The proposed placement is based on the dimensions of the nearest shapes that
are found in the horizontal and vertical projection of the mouse pointer position.
When no shapes are found, some arbitrary default size is proposed, centered around
the mouse pointer (Fig. 17(a)). On the other hand, if some shape is found and the
mouse pointer is sufficiently close to that shape, the new element is placed flush
next to it, taking on the same height or width, respectively (Fig. 17(b)). If in both
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