Cursor caging: Enhancing focus targeting in interactive fisheye views

Fisheye view is an effective approach to visualizing and navigating large data sets by offering both local details and global context in the same view. However, by using different magnification factors for detail and context information, fisheye view also leads to new usability issues, one of which is the focus targeting difficulty. This challenge happens when a user tries to select a target to either shift the focus to a new place or chooses the target. Because of the magnification factors applied to the fisheye view, the target moves when the cursor moves, and consequently, the moving distance the cursor actually needs to travel to reach the target does not match the distance between the cursor and target shown on the screen. Task accuracy and efficiency can be affected. This paper analyzes the mechanism of this difficulty and proposes a new technique, cursor caging, as a method to alleviate the focus targeting difficulty in interactive fisheye views. This technique extends the fisheye magnification approach from one element to a focal region, which can contain several elements, and allows the mouse cursor to move freely inside this region without affecting the magnification of objects inside the focal region. In addition to the mathematical representation of this technique, we also develop two designs that incorporate the cursor caging concept in fisheye views, and describe a usability study on the technique. Our results showed that cursor caging can significantly improve the task completion time and reduce the error rate in focusing targeting tasks.