TreeMapLayout

Quicksilver uses tree maps for its visualization. As part of the development of Quicksilver, we implemented and contributed a tree map layout to Roassal, an agile visualization engine included in Pharo.

Roassal is included in all Pharo releases, if one would like to work with he bleeding edge developement version though, the code can be found here: http://smalltalkhub.com/#!/~ObjectProfile/Roassal

Lets look at an example how the TreeMapLayout can be used. (These and more can be found in ROTreeMapLayoutTests).

First let us draw a tree with a tree layout as reference:

| view |
view := ROMondrianViewBuilder new.
view nodes: (0 to: 999).
view edgesFrom: [ :each | each // 10 ].	
view treeLayout.
view open. 

This code draws us a very simple, but very large regular tree from the numbers 0 to 999.

The tree is very wide, a tree map seems to fit much better to look at the tree structure. So let us see what the same looks like as a treemap:

| view |
view := ROMondrianViewBuilder new.

"The treemap should have a dimension of 500 by 500"	
view shape size: 500.

view nodes: (0 to: 999).
view edgesFrom: [ :each | each // 10 ].

"The weights we use to draw the treemap are the models itself: the numbers."	
view layout: (ROTreeMapLayout withWeightBlock: [ :e | e model ]).
view open.

In this case, we get a much better overview of the data when using a treemap instead of a tree.

Now as final step, let us look at a more useful example. We will create a treemap of all subclasses of the Collection class, weighted by lines of code (LOC):

view := ROMondrianViewBuilder new.

"Adding basic interaction capabilities to nodes: 
 - Add a menu item which lets one explore the model of the node.
 - Another menu item which lets one browse the class represented by the node.
 - Show the node name on hover."
view interaction 
	item: 'Explore Class' action: #explore;
	item: 'Browse Class' action: #browse;
	popupText: [ :node | node ].

"The treemap should have a dimension of 500 by 500."	
view shape size: 500.

"Our nodes are all subclasses of Collection."
view nodes: Collection withAllSubclasses.
view edgesFrom: #superclass.

"The weights we use to draw the treemap are the classes lines of code (LOC)."
view layout: (ROTreeMapLayout withWeightBlock: [ :e | 
	e model numberOfLinesOfCode ]).
view open.
Last changed by admin on 21 April 2009