**flexmenu**

Source: https://gentoo.com/tcl/flexmenu.tcl  (version 1.1)

[bll] 2018-9-20: An alternative menu system.

****Disadvantages:****

Does not work with `.toplevel configure -menu .mymenu`.  Tk uses the internal menu API to attach menus.
flexmenu cannot work with the `-menu` option.  

Must use pack or grid (or place) to attach the menu.  Converting an existing program to use flexmenu 
could be quite painful.

The main menu must be created with either `-type menubar` or `-type menuleft`.

It has not been tested much.

****Features:****

   * Checkbuttons and Radiobuttons are ttk widgets.
   * Supports left side menus (`-type menuleft`).
   * Scrolling menus (`-maxheight`).
   * Configure `-columnbreak <value>` at the menu level to automatically break every <value> items.
   * `-keepopen` option will leave the menu open after invoking an item.
   * `-acceleratorfont`, `-acceleratorforeground` and `-acceleratoractiveforeground` options.
   * `-activerelief` option.
   * `-hidearrows` option.
   * `-hideaccelerators` option.
   * Uses ttk widgets where possible.
   * Is more dynamic than the standard `menu`.  Many things can be reconfigured and the changes will be picked up.

****Item Features:****

   * Any widget can be put into the menu (`.mymenu add widget -widget .mymenu.mycombobox`).
   * Margin images (`-marginimage`).  It is quite common nowadays to use small icons on the left margin of the menu as an aid for the user.
   * Accelerator labels are automatically generated based on either an `&` prefix in the label, the `-underline` option, or the `-accelerator` option.
   * Accelerator bindings are automatically generated.
   * `-activerelief` option.

****Notes:****

Ignored: `-bitmap`, `-tearoff`, `-tearoffcommand`, `-title`, `-selectcolor`.

`-hidemargin` works properly on a per-entry basis. `menu` seems to treat it as a menu option even though it is specified per entry.
I think `-hidemargin` would be better off as a menu option rather than an item option, but backwards compatibility is an issue. 

****Problems:****

May be overeager in generating accelerator labels.  The user may not want accelerator labels displayed for every item.

Has not been tested much.

At this time, flexmenu does not check to see if the entire menu is visible, and does not do any relocation of the menu.

****Known Issues:****

'''Fixed in 1.1''': Active item highlighting for scrolling menus is not working right.

The accelerator key prefix is set to `Alt`.  This needs to be set correctly for Mac OS X, but I do not recall
which meta key the Mac sends.

****Example:****

======
package require Tk
source flexmenu.tcl

# standard checkbutton widgets
# -keepopen set
flexmenu .mcb -keepopen true
.mcb add checkbutton -variable ::x -text Check -onvalue 0 -offvalue 1 \
    -accelerator Ctrl-4
.mcb add checkbutton -variable ::x -text Check -onvalue 0 -offvalue 1 \
    -accelerator Ctrl-5 -indicatoron false
.mcb add checkbutton -variable ::x -text Check -onvalue 0 -offvalue 1 \
    -state disabled

flexmenu .mrb -keepopen true
.mrb add radiobutton -variable ::x -value 0 -text Radio-0 \
    -accelerator Ctrl-2
.mrb add radiobutton -variable ::x -value 1 -text Radio-1 \
    -accelerator Ctrl-3
.mrb add radiobutton -variable ::x -value 2 -text Radio-2 \
    -accelerator Ctrl-4 -state disabled

# automatic column break every fifth item.
# frame widgets in the menu
set clist {#000000 #ff0000 #00ff00 #0000ff #ff8000 #ff0080 #80ff00
    #00ff80 #8000ff #0080ff #ffff00 #ff00ff #00ffff #ffff80 #ff80ff
    #80ffff #ffffff #ff4040 #40ff40 #4040ff #404040 #808080 #ffff40
    #ff40ff #40ffff}
set col [flexmenu .col -columnbreak 5]
set count 0
foreach {c} $clist {
  set tf [frame .col.x$c \
      -background $c -relief raised -borderwidth 2 \
      -width 20 -height 20 ]
  .col add widget -widget $tf -hidemargin 1
  incr count
}

# scrolling menu
# frame widgets in the menu
set clist {#000000 #ff0000 #00ff00 #0000ff #ff8000 #ff0080 #80ff00
    #00ff80 #8000ff #0080ff #ffff00 #ff00ff #00ffff #ffff80 #ff80ff
    #80ffff #ffffff #ff4040 #40ff40 #4040ff #404040 #808080 #ffff40
    #ff40ff #40ffff}
set colsc [flexmenu .colsc -keepopen true -maxheight 5]
foreach {c} $clist {
  set tf [frame .colsc.bbb$c \
      -background $c -relief raised -borderwidth 2 \
      -width 20 -height 20 ]
  .colsc add widget -widget $tf -hidemargin 1
}

# combobox widget
flexmenu .mw 
ttk::combobox .mw.cb -values {aa bb cc dd ee ff gg} \
    -textvariable ::y -state readonly -width 5
.mw add widget -widget .mw.cb

# main cascade
flexmenu .m
.m add cascade -menu .col -label {Colors}
.m add cascade -menu .colsc -label {Scrolling Colors}
.m add cascade -menu .mcb -label {Check Buttons}
.m add cascade -menu .mrb -label {Radio Buttons}
.m add cascade -menu .mw -label {Widgets}
.m add command -label E&xit -command exit

flexmenu .mtop -type menubar
.mtop add cascade -label Test -menu .m
.mtop add command -label E&xit -command exit
pack .mtop -side top -fill x -expand 1 -anchor nw
frame .f -width 200 -height 200 
pack .f
======