There are two ways to specify constraints in
a style sheet:
- In an external file that contains the constraints
- By means of style rules in the style file directly
When you do not use a diagram component with
style sheet capabilities, you can still use constraints.
Writing style rules that specify constraints is very powerful but
complex. It is illustrated in section For
experts: specifying constraints in CSS directly (HL). This topic
concentrates on specifying constraints in an external file.
In the CSS file, you can write:
GraphLayout {
graphLayout : "Hierarchical";
constraintsURL : "url(Constraints.txt)";
}
This means that the layout constraints are specified in a separate
file named
Constraints.txt
. This file contains the constraint in a very simple format, for
example:
SameLevelConstraint {
firstNode: node2
secondNode: node5
}
RelativeLevelConstraint {
lowerSubject: { node5 }
higherSubject: { node9 }
priority: 50.0
}
LevelRangeConstraint {
subject: { node11, node12 }
minLevel: 3
maxLevel: 4
}
The complete example can be found at:
The style files are in the subdirectory
data
. The example shows how to specify constraints by loading an
external file as well as how to specify constraints by writing
style rules directly.