Roassal is a visualization engine largely used within the Pharo community. Roassal is used to visualize any set of data. In particular, it is often used to visualize large software source code base to assess their internal quality.
What is the goal of the tutorial?
The following tutorial has been designed to introduce users to the Roassal visualization engine. At the end of the tutorial, users will be familiar to the basic API of Roassal as well with the domain-specific builders. Users will know how to visualize objects within a domain to enable exploration and analysis. They will visualize properties and relationships using the features offered by the engine such as shapes, layout, color, size, interactions (to name a few). Users should also be able to know where to find answers to further questions and to get deeper knowledge in the engine. Let's start.
Roassal is easy to install and the installation will not polute your file system. Simply download Moose as indicated on http://moosetechnology.org. You need three downloads: Moose 6.1 image, Pharo60.sources, and a virtual machine. The virtual machine depends on your operating system.
On Max OSX, you can open Moose (which contains Roassal) by drag and dropping the file moose-6.1.image on top of the virtual machine. You should obtain something like in Figure .
1.2. Hand's on: Basic Roassal API
In the following section we are going to incrementally use the basics of the Roassal API. In each step we (1) define a goal, (2) list required actions to achieve the goal, (3) show the changes to be made to the source code of the previous step (second step on), and (4) how the code of the visualization should look like after the changes (that you can copy/paste).
1.2.1. View, Shape, Layout and Interaction
Visualize the Collection class hierarchy using a grid layout
Create an RTView object
Create elements using an RTBox shape to represent each class
Add the elements to the view
Lay the elements out using an RTGridLayout
1.2.2. Size, Color and Customize Popup
Map to the size and color of each box metrics of classes
When creating the elements send the messages color:, size:
Customize the text: of the popup
Show the class hierarchy using edges and a tree layout.
Add edges from the superclass to the subclass
Change the layout to a RTTreeLayout
Adjust the visualization using normalization to map color and size, and apply a more scalable layout.
Remove messages color: and size: sent during the creation of elements
Add an RTMetricNormalizer object to map the color and size
Change the shape of elements to use RTEllipse
Push edges to the back of the circles
1.2.5. Bezier Edges
Add a different kind of edges to depict class dependencies
Add bezier edges from each class to dependent classes
1.3. Does it scale to larger software?
Let's see. Now we are going to load a model of Tomcat into the Moose image and ajdust the visualization to analyze it. The model contains a description of the main properties of the software such as classes, methods and invocations. Also, we are going to link the model to the software's source code, so we can inspect it within the visualization.
In Moose open from the menu the Moose panel and load the MSE model file
Once the model is loaded, decompress the zip file that contains the sources. In the panel right-click the model and select utilities>Set root folder, then specify the local folder that contains Tomcat's sources.
1.3.2. Visualizing Tomcat's class hierarchy and dependencies
Show how the visualization performs on larger software (~1 min.).
Adapt the data source to point to the classes within the Tomcat's model
Modify the calls accordingly to obtain the dependent classes (other calls use similar signatures)
1.3.3. Adapting the visualization for larger software
Distinguish Tomcat classes from libraries (Java core and external libs) and change the layout to ease the analysis of dependencies (~2.5 mins.)
When creating elements use the message color: to distinguish the source of a class (whether or not it belongs to Tomcat) and remove the previous definition from the normalizer
Change the layout to RTForceBasedLayout
2.1. Using Roassal API build a visualization to analyze Tomcat's class hierarchy.
2.1.1. Build a visualizatiom that uses a Treemap to depict class hierarchy and that maps to the area of the tiles the number of lines of code of the class they represent. Use two different colors to identify the classes that contain deprecated methods and the ones that might be tests. Hint: (1) you can assume that the name of test classes contain the Test word. (2) Include in the visualization stubs of the Java core and libs classes (.e.g., Object). (3) Notice that the model of the methods of a class contain its annotations.
2.2. Polymetric Views provides insights of the various aspects of a software by mapping multiple metrics to the attributes of rectangles that represent software entities (e.g., classes). In this exercise you have to create a visualization that maps Tomcat classes to rectangles. Each rectangle has to encode: (1) the #hierarchyNestingLevel in its height, (2) the #numberOfAttributes to its width, (3) #fanOut in its color; and the x-position of rectangles must encode #fanOut and y-position =#fanIn. The resulting visualization should look like the one below. Analysis of the visualization and highlight insights that you found. Hint: How fanOut relates to other metrics?
Links to resources for more detail on the Pharo language, the Moose plataform and the Roassal visualization engine.