** Summary **

[HJG] 2016-01-28: This is a fork of [A little value dialog] by [Richard Suchenwirth],
a small edit-value-dialog.

The immediate upcoming intended use is in [MINISS - Mini Spread Sheet],
together with that nice and short [m+]-menu routine. 

** Description **

This is a custom dialog - a toplevel that prompts for a value.

I have some ideas on how to modify the original value_dialog - routine,
so I made a separate page here:

   * Avoid double-returning the result (return + global var)
   * Undo/discard when pressing the Cancel-button
   * controlling the position of the dialog
...

-----
**Code**
======tcl
  package require Tk

 #
 # Input-Dialog: (from http://wiki.tcl.tk/8692 "A little value dialog" by R.Suchenwirth)
 #
 proc edit_val {string } {
    set w [toplevel .edit]
    wm resizable $w 0 0
    wm title $w "Edit cell"

    label  $w.l -text    $string
    entry  $w.e -textvar ::val -width 20
    set old  $::val

    button $w.ok     -text "  OK  " -command {set ::done 0}
    button $w.clear  -text "Clear " -command "set ::val {}"
    button $w.cancel -text "Cancel" -command "set ::val $old; set ::done 1"

    bind   $w.e <Return> {set done 1}
    bind   $w.e <Escape> "$w.cancel invoke"

    grid $w.l  -    -        -sticky news
    grid $w.e  -    -        -sticky news
    grid $w.cancel  $w.clear  $w.ok

    raise $w .
    focus $w.e

    vwait ::done
    destroy $w
    return $::done
 }

 # Demo:

 wm withdraw .
 update
 wm deiconify .;           # window-manager needs to update size and position

 set zz [wm geometry .];   # get size and position
 wm title . $zz

 set val 123;  # global var, for use with `-textvar`
 set done -1

 set res [edit_val "Enter value:"]
#puts  val:$val
 pack [ label .l -text "Result: $res --> '$val' " -pady 30 -padx 30 ]
 focus -f .
======
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**Comments**

Features:
   * acts on the global variable `val`, because `-textvar` uses global vars.
   * uses the global variable `done`, because [vwait] uses global vars.

   * The dialog comes up on top of the parent-window, focus on the entry-field.

   * Return-key for OK.
   * ESC-key for Cancel = exit dialog with no changes.

   * Returns 0 if OK was pressed, 1 if cancel was pressed, (2+ for errors)


-----

**See also** 
   * [entry]
   * [Mentry] - [tklib]
   * [ttk::entry]
   * [widget:entry]
!!!!!!
!!!!!!
   * [Tktable]
   * [Simple Tktable]
   * [Inserting an Entry Widget in TkTable] - This looks like a better start to display a spreadsheet.
!!!!!!
!!!!!!
   * [A little value dialog]
   * [Another little value dialog]
   * [A not-so-little value dialog]
!!!!!!
!!!!!!
   * [Simple Entry Demo] - Tk-demo: label, entry, button, image. Calculation, but no validation .<<br>>Uses a simple layout with frames and pack: enter 3 numbers, show their sum and product.
   * [grid] - the "Basic Example" for an entry-form with several fields, using labels and entries.
!!!!!!
!!!!!!
   * [Integer entry validation with range check]
   * [Entry Validation]
   * [Entry Field Processing]
!!!!!!
!!!!!!
   * [how do i do $$var - double dereferencing a variable]
   * [Practical Introduction to Upvar and Uplevel]


<<categories>> GUI | Dialog | Widget