Debugging Your Algorithm

The Eclipse Layout Kernel SDK provides two views built specifically for debugging your layout algorithm: the layout graph view and the execution time view.

Layout Graph View

The layout graph view registers with the DiagramLayoutEngine to be notified whenever a layout run finishes and displays the layout graph exactly as it comes out of the layout algorithm, without any modifications applied. Use this view to check if your algorithm works and if you got the coordinate system right.

Note that the layout graph view allows you to export the displayed graph as a PNG image file. It also allows you to display debug graph files (see below).

Open the layout graph view by clicking Window -> Show View -> Other and select Layout Graph from the Eclipse Diagram Layout category.

Layout Time View

The layout time view registers with the DiagramLayoutEngine to be notified whenever a layout run finishes and displays which steps the layout run consisted of and, if enabled, how much time each step took to run. Measuring these execution times has to be explicitly enabled in the preferences:

Enabling layout time measurements

Once enabled, the view displays two values for each item: the time and the local time. The former is the amount of time spent for an item and all of its sub-items. Local time is the time spent on the item alone, without any sub-items (this value is omitted for items that do not have any sub-items, since it would be equal to the normal time value anyway).

To take advantage of the layout time view, your algorithm must make proper use of the IElkProgressMonitor passed to it. The tree of progress monitors (and sub-monitors) is what gets displayed in the layout time view. Be sure to do something like this:

monitor.begin("My rather good layout algorithm", 2);

executePhase1(monitor.subTask(1));
executePhase2(monitor.subTask(1));

monitor.done();

Open the layout graph view by clicking Window -> Show View -> Other and select Layout Time from the Eclipse Diagram Layout category.

Debug Files

The ELK preference page (see above) contains another setting: Debug graph output. Enabling this will cause the DiagramLayoutEngine to save the layout graph just before automatic layout is run. The graphs are placed in your user folder, in a subfolder called elk/diagram_layout_engine. The graph files can be displayed by the layout graph view, even though that usually is not very helpful since they may not contain any valid layout data yet.