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2.1 Understanding the Drawable

The main visual component in the SLOG-2 visualization program, Jumpshot-4, is the timeline canvas which is zoomable and scrollable in both horizontal and vertical axes. The timeline canvas can be thought of as a TIMELINE vs TIME coordinate system. Each point on the canvas is identified by two numbers, a timestamp and a timeline ID. The canvas is where the graphical objects contained in SLOG-2 file are being drawn on. These objects are called Drawables. There are 2 kinds of drawable objects. They are Primitive and Composite drawables. The primitive drawables are the simplest drawables and are considered to be basic elements of SLOG-2 file. They are categorized based on their topological structures. Currently, there are 3 topologies supported in SLOG-2. They are State, Arrow and Event. Both state and arrow are drawables identified by 2 points in the timeline canvas, i.e. a pair of (timestamp, timeline ID) coordinates. State's start timeline ID is the same as its final timeline ID, but arrow is different from state in the way that arrow's start and final timeline IDs may be different. Event consists of only 1 point in the timeline canvas, i.e. it has only 1 timestamp and 1 timeline ID. Composite drawable is more complicated and is constructed by a collection of primitive drawables2.1. In order to centralize the properties of drawables, all the displayable attributes of a drawable are stored in its corresponding Category object, e.g. color, legend name, topology and other shared description of a drawable. Both the category and drawable definitions are stored in the SLOG-2 file. These definitions are interpreted and displayed by the display program, Jumpshot-4.

One of the distinct features of Jumpshot is that it uses nested states to show the relationship of functions in the call stack, i.e. nested states corresponds to the nested subroutine calls. Current implementation of the SLOG-2 format stores some of the state nesting information to optimize the performance of the visualization program.



Footnotes

... drawables2.1
In general, composite drawable can be seen as composed of other simpler composite drawables.

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Next: 2.2 Understanding the Preview Up: 2. Data Model Previous: 2. Data Model   Contents