[TCLCORE] TIP #740 Enhanced Treeview Widget Update

[Brian O'H. <bri...@co...>]

I've made much progress in addressing many of the changes mentioned in 
previous discussions on TIP 740 in addition to a few new features. Some 
of the big ones are:

1. Fixed the long-standing issue with Treeview auto row height sizing. 
The default is to now auto size rows based on the theme and font. There 
are also manual options to control these too.

2. Revamped the focus ring implementation to use the focus ring element. 
This made it possible to get the focus ring to look accurate in the Aqua 
theme.

3. Fixed many of the issues with the CheckTreeview style. See below for 
last open issue.

4. Made a bunch of theme improvements.

5. Added an example cell edit function to the new treeview demo.

6. Added B1 double click on divider will auto size column to contents. 
Alt or Option plus B1-Double will auto size all columns. Works best when 
all columns are set to -stretch 0. Added an option to the demo to set 
all columns stretch to true or false.

See the repo timeline for all of the changes.


Open Issues

1. There are still some improvements needed for the Aqua theme. (I need 
some help from the Mac folks on these.)

    a. For the CheckTreeview style, selected check-boxes are all white
    or not visible.

    b.The open/close indicator, sort indicator, buttons, checkbutton
    indicators, radiobutton indicators, etc. don't scale with tk scaling
    changes.

    c. The Aqua theme seems to ignore the heading -anchor option.
    Changing the anchor is needed to match Finder which uses left
    justification (w anchor).

2. Windows theme

    a. I think I figured out how to get the sort arrows at the top
    center of a heading cell. I need feedback on whether that is
    desirable or not.

    b. I plan to change to use Chevron type open/close and sort
    indicators like Windows 10/11 use. This seems to closely match what
    Aqua is doing too. Maybe it would be good to add this to
    ttkElements.c so all themes can use it. Any thoughts?

    c. Windows theme elements don't seem to scale either.

3. Need feedback on column resizing issues in 
https://core.tcl-lang.org/tk/tktview/62a760c20c.

4. I need feedback on the core function changes outlined in the TIP too.

Thanks


TIP: https://core.tcl-lang.org/tips/doc/trunk/tip/740.md

Code: https://chiselapp.com/user/bohagan/repository/Treeview/index