Geoscience Reference
In-Depth Information
3.2 Finger-Count Shortcuts: a novel interaction technique for QGIS
Gestural interaction is especially relevant for interactive surfaces not only
for practical reasons (such as the absence of a mouse and a keyboard), but
also because of various advantages such as ability to exploit spatial mem-
ory effectively (Wobbrock et al. 2009). Most gesture vocabularies on in-
teractive surfaces are based on straightforward connections with their ref-
erents, this making them easy to learn. However, the number of “natural”
gestures is limited and too small for selecting the numerous commands that
are needed in real applications. Arbitrary gestures (gestures without direct
connections with their referents) offer more possibilities, but require guid-
ance to learn. Interaction techniques such as Marking menus (Kurtenbach
et al. 1991) or their variants (Bailly et al. 2008), which are based on arbi-
trary gestures, have been proved very efficient, because they combine cir-
cular menus (for guidance) and gestural interaction. This makes it possible
to favor a fluid transition from novice to expert usage. However, a com-
mon problem with Marking menus on interactive surfaces is that they use
drag events. They may thus conflict with gestural interaction techniques
based on pan, rotate or pinch gestures.
Finger-Count Shortcuts (Bailly et al. 2010) is an alternate technique, which
was recently proposed for avoiding those problems. It makes it possible to
use common pan, zoom, rotate gestures together with arbitrary gestures for
selecting numerous commands. It is based on a very simple principle: the
selected command just depends on the number of fingers that the user
places on the interactive surface using his left hand and his right hand.
Besides, as explained below, this technique fits well with traditional menu
systems, so that it can serve to enhance existing systems without the need
to redesign them from scratch. This paper proposes an improvement of
Finger-Count Shortcuts that is specifically adapted for the QGIS software.
Finger-Count Shortcuts (FC shortcuts) work as follow. Each N-finger
touch with the non-dominant hand is associated with a menu of the menu-
bar, the correspondence being recalled to users by a digit displayed next to
each corresponding item (
Figure 4
). Likewise, the dominant hand is asso-
ciated with an item in the currently selected menu. Hence, the user simply
selects an item by putting N fingers with each hand in contact with the in-
teractive surface. The corresponding command is activated when the user
lifts all his fingers. This technique makes it possible to quickly explore the
different menus just by adding or removing the appropriate number of
fingers. The current operation can be canceled by first releasing the non-
dominant hand.
