For various reasons you cannot do it inline. Here is one way to center
import java.awt.*
import groovy.swing.*
sb = new SwingBuilder()
sb.build {
f = frame(pack:true) {
label "<html>" + (("This is a very long label."*3) + "<BR>")*5
}
Point cp = GraphicsEnvironment.localGraphicsEnvironment.centerPoint
f.location = new Point((int)(cp.x - f.width), (int) (cp.y - f.height))
f.show()
}
The reason you cannot set it in the attributes is that when the attributes are evaluated a child node has not yet been created or stored anywhere. One alternative is to set it as part of the child content block:
frame(show:true)
{
label "<html>" + (("This is a very long label."*3) + "<BR>")*5
current.pack()
Point cp = GraphicsEnvironment.localGraphicsEnvironment.centerPoint
current.location = new Point((int)(cp.x -current.width/2), (int)(cp.y - current.height/2))
}
(current is a meta-variable for the containing node).