to Flex Visual Graph Library

hmm - strange thing: i can't change default layout to "Hierarchical"
in initData function.... if i do there is

Error: Invisible root node, this is probably due to wrong
initialisation of nodes or wrong defaults
at org.un.flex.graphLayout.layout::HierarchicalLayouter/layoutPass()
[C:\Documents and Settings\Bellone\My Documents\Flex Builder
3\graphLayout\org\un\flex\graphLayout\layout\HierarchicalLayouter.as:
177]
at org.un.flex.graphLayout.visual::VisualGraph/draw()[C:\Documents
and Settings\Bellone\My Documents\Flex Builder 3\graphLayout\org\un
\flex\graphLayout\visual\VisualGraph.as:1096]
at VGExplorer/updateScale()[C:\Documents and Settings\ilya\My
Documents\Flex Builder 3\vgExplorer\VGExplorer.mxml:637]
at VGExplorer/setLayouter()[C:\Documents and Settings\ilya\My
Documents\Flex Builder 3\vgExplorer\VGExplorer.mxml:502]
at VGExplorer/initData()[C:\Documents and Settings\ilya\My Documents
\Flex Builder 3\vgExplorer\VGExplorer.mxml:172]
at VGExplorer/init()[C:\Documents and Settings\ilya\My Documents\Flex
Builder 3\vgExplorer\VGExplorer.mxml:137]
at VGExplorer/getResultOk()[C:\Documents and Settings\ilya\My
Documents\Flex Builder 3\vgExplorer\VGExplorer.mxml:1147]
at VGExplorer/__serverXML_result()[C:\Documents and Settings\ilya\My
Documents\Flex Builder 3\vgExplorer\VGExplorer.mxml:1142]
at flash.events::EventDispatcher/dispatchEventFunction()
at flash.events::EventDispatcher/dispatchEvent()

Such problem (Invisible root node....) often throwed when changing
some parameters (node, edge styles) can anyone explain what is that
means?

to Flex Visual Graph Library

Hi Seth,

yes, the issue is that invisible nodes are not rendered and
do not exist for the sake of the layout calculation. Invisible
nodes are usually nodes which are farther away from the current
root node than the current degree of separation setting.
There are some exception, e.g. when you turn history on,
all nodes previously visited will still be visible, even if
farther away.

Invisible nodes also typically do not have a DisplayObject associated
with it.

The reason for all this, is that if you have a large graph with 100s
or
1000s of nodes, having so many DisplayObject slows things down.
Also if they should not be displayed, they should be ignored
by the layouter.

Now one thing most layouters have in common is that they require
a root node (most actually work only on trees and thus need a root).
This also means the root must be visible for them, so it is available
for the layout calculation.

The source of the problem is that probably the root node is not
set to valid root node at the moment during whatever change was
performed.

Whenever you change something, just make sure the current root
node is still valid before you do the layout calculation.

Hope this gives you sufficient background to track down your
problem.

Cheers,
Daniel

Ілля Романенко

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