Auto open tree node during drag and drop operation
Recently one of the project I’m working requires this feature, during a drag and drop operation, when user drag the item over and stay on top of one node in the Tree component for a second or two, that node will be automatically opened, just like those found in Windows Explorer or Outlook.
It sounds easy but actually not, it’s part of the huge revision we did on Tree component, another interesting thing to note is when dragging the item over one node, that node’s background is highlighted, instead of the flex-standard-drag-over behavior: showing a cross-line on top or bottom of the node.
By providing this drag-over-highlight, user got a feeling of s/he is actually dropping the item “into” that node, instead of on top or below that node, small things but have huge impact on user experience, I would really love to see this be integrated into the framework code someday.
Back to the auto open thing, ended up we totally rewrote the logic inside Tree.showDropFeedBack() and calculate which item is rollovered then see if we need to open it or not.
It’s always fun hacking the framework code and achieve things like this 
