**flexmenu**

Source: https://gentoo.com/tcl/flexmenu.tcl

[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 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.

****Known Issues:****

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
======