Annual Report 2010 - Fachgruppe Informatik an der RWTH Aachen ...

Stacksplorer: Understanding Dynamic Program Behavior
Jan-Peter Krämer, Thorsten Karrer, Jonathan Diehl, Jan Borchers
To thoroughly comprehend application behavior, programmers need to understand the
interactions of objects at runtime. Today, these interactions are often poorly visualized in
common IDEs except during live debugging. In an exploratory user study we could confirm,
that programmers are often unsatisfied with available tools for code browsing, because the
common file-based representation of source code does not reflect how methods call each
other at runtime to create the application behavior developers intended.
The information about potential call stacks can mostly be obtained from the source code.
Stacksplorer introduces a novel visualization technique for this information and allows to
navigate through these potential call stacks. It is realized as a plugin for Xcode, Apple’s
standard IDE.
The figure below shows the user interface of Stacksplorer. The central editor is equivalent to
Xcode’s standard editor, retaining all its features and functionality. The method, in which the
cursor is placed, is called focus method. The left column shows methods calling the focus
method, the right column shows all methods called from the focus method.
Besides navigating through a class by scrolling vertically in the editor, our design allows
navigating horizontally through the call stack, by clicking a method in one of the side
columns. For example, navigating to a method that calls the focus method, will cause all 3
columns to shift to the right. The method that was selected moves to the center and opens in
the central editor, the previous focus method appears in the list of called methods to the right,
and the left column is updated with new information. Important paths through the code may
also be stored for later reference.
Initial results of a user study, which tests quantitatively if users can solve tasks faster using
Stacksplorer than without it and qualitatively how satisfied users are with our plugin, indicate,
that our visualization technique is highly appreciated and helps users to perform maintenance
tasks in large software more efficiently.
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