[Tile-dev] Upcoming treeview changes

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

First off: the syntax of the [$tv identify] command is
being replaced with something more sensible.

The new syntax is:

| pathname identify _component_ _x_ _y_
|     Returns a description of the specified component under the point given
|     by x and y, or the empty string if no such component is present at
|     that position. The following subcommands are supported:
|
|     pathname identify row _x_ _y_
| 	Returns the item ID of the item at position y.
|
|     pathname identify column _x_ _y_
| 	Returns the data column identifier of the cell at position x.
| 	The tree column has ID #0.


More subcommands will be added as needed, these two seem
to be the most useful.  The old, horrible, 4-argument form
[$tv identify $x $y] will stick around for a while, but
I hope to phase it out as soon as it's convenient to do so.

Next: the built-in selection behavior is only appropriate
for (at most) 75% of the typical use cases (see #1328192,
#1389202).  To make things worse, it's really, *really* hard
for applications to change things -- partly because [$tv identify]
is so horrible, but mostly because the selection logic
is tightly coupled to the rest of the bindings.

So, new plan: The ttk::treeview's default bindings will not
include any behavior for modifying the selection (this is
how the BWidget Tree works).  There will be a small set of
predefined selection modes (to be determined, will probably
include 'single', 'multiple', and 'extended' a la the core Listbox
widget).  Selection modes can be activated with:

    ttk::treeview::selectMode $tv $mode

This procedure will (probably) be implemented by adjusting
the widget's bindtags; I haven't worked out the details yet.

As a transition strategy, the default bindings will remain
as they are for the rest of the 0.7 series, and [ttk::treeview::selectMode]
will be available (initially) as a no-op.  Existing code
should add calls to [ttk::treeview::selectMode $tv multiple]
at their earliest convenience to ensure forward-compatibility
when 0.8 comes out.


Sound reasonable?  Any comments?


--Joe English

  jen...@fl...