2.4. A graphic viewer based on multiple tool balls
With the above-mentioned tool balls, a new GUI for graphic
viewers can be created with multiple tool balls aligned in a circle,
which is called the “tool area” in this study. The circular arrangement
of multiple tool balls uses a pie menu (Hopkins,1991). The pie
menu of the late 1980s is a circular context menu where the
selection depends on direction (Callahan et al., 1988). Compared to
traditional linear menus, pie menus enjoy the advantages by
reducing target seek time, lowering error rates by fixing the
distance factor and increasing the target size. It is said that pie
menus are faster and more reliable to select from than linear menus
because selection depends more on direction and less on distance
(Shneiderman et al., 1991).