[Tile-dev] Tree API draft round 2

[Joe E. <jen...@fl...>]

Did some more work on this over the weekend.  I'm pretty happy
with the current data model; the primitives provided seem just
about right.

The display and interaction model needs work next.
At a minimum, the widget should support an 'active' item
and a set of 'selected' items like the listbox widget.
We might want to support column selections as well.

It also needs a set of virtual events and/or callbacks
to report interactions, and a way to associate commands
with column headings, plus whatever internal mechanisms
are necessary to make headings look and act like pushbuttons.

Jeff Hobbs made a suggestion about item tags.  I'm waiting
for him to elaborate on that idea :-) but it sounds like
a promising approach.

If anyone has use cases for the widget, now would be a good
time to post them.


Updated manpage here:

    <URL: http://tktable.sourceforge.net/tile/doc/treeview.html >

New stuff since first draft:

    + Added 'column' command to query/configure column attributes.

    + Added 'set' command to query/set item values.

    + Added 'exists' command

    + Added 'move', 'next', and 'prev' commands


Changes since first draft:

    + The 'insert' command now has the form:

	  $tree insert $parent $index ?-id $id? ...options....

      This worked out better.

    + 'remove' is now 'detach' as per AKU's suggestion.

    + 'delete' now takes a list of items.

    + 'children' takes an optional fourth argument; if supplied
      it replaces the list of children.

    + -columns is always a list of column names.  It's also
      a read-only option now, and can only be set at widget
      creation time [*].

    + The -width option is gone; instead the width is calculated
      from the sum of the widths of the -displaycolumns and
      the tree column #0 [**].

    + As discussed earlier, 'itemconfigure' and 'itemcget'
      have been replaced with an 'item' data accessor.
      'open', 'close', and 'opened' widget commands have been
      replaced with '-open' item option.

    + Clarified meaning of out-of-range $index values:
      if $index < 0, insert at the beginning, if >= #children
      append to end.


--Joe English

  jen...@fl...


[*] The main reason for making -columns readonly is to prevent
the widget from getting into an inconsistent state under certain
error conditions.  If this is a problem, I'll try to figure
out how to avoid the inconsistency or just live with it --
it's not a fatal condition, just a possibly confusing one.

[**] -width will probably need to be added back in again later;
I anticipate problems with interactive column resizing.