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Tom Nies

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TreeView Drag and Drop

In prior releases it was too easy to get into trouble when dragging and dropping items or subtrees between two different TreeViewCtrls. There was a cluster of ARs on this topic, so we decided to take all of them into account at the same time and really rework this area. Here is a list of the related ARs closed for 8.4:

55761    Dropping a dragged item from a treeview on a blank area of the treeview gives an unhandled exception

58126    Drag/Drop between two TreeViews throws an UHE: Message not understood: #listIndex

58168    TreeView-Option “Allow Drag” does not work (or erroneous)

58346    Drag and drop treeview nodes between different treeviews

60642    TreeView Sub-nodes disappear after inserting a node in subnode and collapsing current node

64519    The method TreeViewNode>>deepSortUsing: does not work in ObjectStudio8

65148    Dropping a treeview node on empty space in another treeview causes duplicate nodes

65149    TreeViewCtrl: use #copyTreeStructure instead of #deepCopy, and create >>copyContentsTo: to copy full contents to another treeview

65185    Dropped node should keep current state (expanded, collapsed) in new treeview

65212    TreeViewCtrl>>removeNode: should use identity comparison to remove the exact specified node and not a similar one

65237    Copying nodes from one to another TreeviewCtrl lost open subnodes below level two

You’ll find some new,  interesting protocol as you’re browsing code related to this, especially in the FormTreeView, TreeViewCtrl and TreeViewNode classes. We always recommend that you carefully review any method overrides you have when updating to a new release, and in regard to this topic you should look particularly closely at your overrides to methods in those classes. There is one significant change in semantics to note as well: the methods >>expand: and >>expandAt: used to actually mean ‘toggle the expanded/collapsed state.’ If you sent #expand: to a treeview that was already expanded, it would collapse. In ObjectStudio 8.4, that behavior is now in the >>toggle: / >>toggleAt: methods. See the release notes for 8.4 for more detail.

For those of you doing drag and drop between treeviews in ObjectStudio, we hope you see significant improvement in 8.4, and as always, we look forward to your feedback.