[sugar] Of TreeViews, TreeModels, and Custom Object Graphs

[Andrew Clunis]

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Hey folks,

I've been having a real bear of a time in implementing a sane and
functional TreeView in Develop to represent the source tree of an
activity.

I opted to use a so-called GenericTreeModel to bind the GTK TreeView to
the "activity/directory/file" object graph Develop maintains in memory
to describe the activity.

However, I've hung up on an issue.  The TreeModel interface specifies
that it (and, by extension, the TreeView) need to be informed when the
data they represent changes.  Thus, I've implemented an observer pattern
in which whenever the directory/file object graph changes it calls a
list of callbacks of interested Develop components.  These callbacks are
given a single argument, the directory that changed.  If a file or
directory is removed, moved, or added the changed handler is invoked on
the parent of that object.  This is intuitive because creating a new
file involves writing to the directory that will contain it.

However, dragging and dropping confounds (after Develop has changed the
object graph, of course) the TreeView and displays the message "There is
a disparity between the internal view of the GtkTreeVew and the
GtkTreeModel." on stdout.

I'm not sure why this can be happening.  Perhaps I made a mistake in
assuming that row-changed will cause the TreeView to rescan the children
of the specified row.  The PyGTK and GTK documentation alike are very
light on information. :(

The Code in question:

TreeModel: http://dev.laptop.org/git.do?p=projects/develop-activity;a=blob;h=52cff8687f03e0485bec7d6535aa16e5e84d53c6;hb=4472bb428afef58bc4efcf74b9bb2b0044e1ed27;f=develop/activity_treemodel.py

TreeView:  http://dev.laptop.org/git.do?p=projects/develop-activity;a=blob;h=07ab77f4f1875916ca96891d2cd8cfc98224beab;hb=4472bb428afef58bc4efcf74b9bb2b0044e1ed27;f=develop/activity_tree.py

Any suggestions?  Thanks!

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Regards,
Andrew Clunis
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