Stuart Marks has written up part II of the three-part series on the scenegraph warning message that you have seen in JavaFX1.2. I covered and linked to the first version previously. It really is a terrific read, and details some of the subtle semantics of bind. Stuart always does such an excellent job describing these subtle issues.
In my earlier post on this topic I hinted that we had found a resolution to the issue surrounding the warning message, I hinted further in some of my replies to comments, and I even left it as sort of a cliffhanger as to what the resolution was. So, here’s the resolution.
We’ve decided that when a node is added to a group, that node is automatically removed from the group that previously owned it, if any. (Let’s call this the “auto-remove” feature.) We’ve also decided to turn off the warning message by default, but to have it be enabled optionally, possibly via a system property, for debugging purposes. Finally, we’ve relaxed the enforcement of some scene graph invariants in cases where the group’s content sequence is bound.
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During the development of our current release, we kept running into this issue. A couple of us wrote code that we thought was reasonable, yet it surprised us when the warning message came out! We had a few hallway conversations from time to time, but a clear-cut answer never emerged. Finally, we realized that we had to get the interested parties in a room and have a knock-down, drag-out meeting to resolve the issue. And so on October 7, 2009, Amy Fowler, Kevin Rushforth, Richard Bair, and I got into a conference room to decide the issue. Three hours later — with no breaks! — we had decided. Actually, it was a great meeting, without a lot of conflict. There were just a lot of issues to cover. Each of us came into the meeting with our initial opinions, but the issues were so close that I think each one of us switched sides at least once during the meeting.
