I still do something wrong with Scrollpane and zoom capability

Question

Hi all!
I thought I was successful in creating a working ScrollPane with centered zoom capability, but now I noticed that it doesn't work like it should, if the content node's PrefSize is larger then the scrollpane's size.
The probleme is: if the contentNode is smaller then everything works how it should. The scrollbars update accordingly to the scale transformation. The scale transformation is applied to a node X and this node is a child of a flowPane node. The flowpane node ist the actual contentNode for the scrollpane.
The node X has a changeListener for node.boundsInParent property and updates the flowpane's prefSize.
Like I mentioned, everything works fine if the node and with that the flowpane's initial prefSize is at most same size like the scrollpane's.
The probleme is that if the scaling is smaller than the scrollpane's size, the scrollbars don't update anymore, they keep the state for the initial prefSize of the flowpane While debugging I noticed that the actual size of the flowpane doesn't change if the changeListener sets the new prefSize to a down scaled size, smaller than the initial size (scalefactor = 1), but the prefSize of the flowpane changes if the scaled size is bigger then the initial size. And I think this behaviour of the flowpane ist stange (actually it is the same for stackpane and maybe for the other panes too).
I couldn't find a way for the case that the initial contentNode is bigger than the scrollpane size.
I didn't expect that implementing a scroll pane with zoom capability would be such a probleme. I really need a solution for this probleme.
EDIT: Ok after a lot of testing I noticed, that StackPane and FlowPane behave like I had described it above, but Pane itself does behave like it should, at least how I would expect it. Now the probleme is, even if the Pane reduces its size and the scrollpane adaptes to it accordingly, the scale transformation is always centered and therefore the node with the transformation will be outside the Pane.
It's like I never find a complete solution for my probleme. Everything I do has one fault.
Thanks in advange.
Edited by: user965407 on 25.12.2011 04:28

Answer 1

ScrollPane documentation (http://docs.oracle.com/javafx/2.0/api/javafx/scene/control/ScrollPane.html) states:
"If an application wants the scrolling to be based on the visual bounds of the node (for scaled content etc.), they need to wrap the scroll node in a Group."
Not sure if that is what is causing your issues or not, but something to consider anyway.
Also, you may want to try running and reviewing this example code (https://gist.github.com/1442298) for a centered node in a scrollpane with various effects and transformations (such as scaling) applied.