[Richard Suchenwirth] 2002-03-13 - Here is a little proc that brings up a username/password
widget, the password field being made unreadable as is usual, and grabs focus until
terminated with "OK", "Cancel" or <Return>. 
It returns a list of two elements: username and password, or an empty list if canceled.

[WikiDbImage login.jpg]

Much can be done to improve this - just take it as a first shot!

 proc tk_login {w {title "Login please"}} {
    toplevel $w -borderwidth 10
    wm title $w $title
    label  $w.u -text "User name:"
    entry  $w.user -textvar _username
    label  $w.p -text "Password:"
    entry  $w.pass -show * -textvar _password
    label  $w.dummy -text ""
    button $w.ok -text OK -command {set _res [list $_username $_password]}
    button $w.cancel -text Cancel -command {set _res {}}
    grid   $w.u $w.user -         -sticky wns
    grid   $w.p $w.pass -         -sticky wns
    grid   $w.dummy x   x
    grid   x    $w.ok   $w.cancel -sticky news
    bind $w <Return> [list $w.ok invoke]
    bind $w <Escape> [list $w.cancel invoke]
    raise $w
    grab set $w
    vwait _res
    destroy $w
    unset ::_username ::_password
    return $::_res
 }
# Silly little test...
 pack [text .t]
 update
 set password ""
 while {$password != "secret"} {
    set userpass [tk_login .login]
    set password [lindex $userpass 1]
 }
 .t insert end "[lindex $userpass 0] logged in\n"

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[KPV] Here's a slight tweak of the above code to get better resize behavior. 
Of course, you could just make the windows un-resizable but I think it's 
better to allow it to get wider. 
Also, there's no need for the dummy label widget to get the spacing you want--just 
use [grid] to create an empty row with ''-minsize'' set.

 proc tk_login2 {w {title "Login please"}} {
    toplevel $w -borderwidth 10
    wm title $w $title
  
    # change the following to 'wm resizable $w 0 0' to prevent resizing
    wm resizable $w 1 0
    label  $w.u -text "User name:"
    entry  $w.user -textvar _username
    label  $w.p -text "Password:"
    entry  $w.pass -show * -textvar _password
    button $w.ok -text OK -width 8 -command {set _res [list $_username $_password]}
    button $w.cancel -text Cancel -width 8 -command {set _res {}}
    grid   $w.u $w.user -     -         -sticky news
    grid   $w.p $w.pass -     -         -sticky news
    grid   rowconfigure $w 10 -minsize 20
    grid   x    x       $w.ok $w.cancel -sticky news -row 11 -padx 2 -pady 2
    grid columnconfigure $w 1 -weight 1
    
    bind $w <Return> [list $w.ok invoke]
    bind $w <Escape> [list $w.cancel invoke]
    raise $w
    grab set $w
    
    focus $w.user

    vwait _res
    destroy $w
    unset ::_username ::_password
    return $::_res
 }

[http://www.frbc-va.org/misc/login.gif]

[Scott NIchols] I like this login window. I tweaked the above to set focus on the user entry.

[RLH]: Gave the buttons a uniform width and padding to make them look better.

[rdt]: Well, the problem that I see with this, is that reducing the size covers the buttons instead of using the left-side space.  To me, this is real no-no!

[RLH]: I just re-ran the second version and it looks better. The original has the buttons side-by-side, a ui design no-no. The second one spaces them and makes the buttons uniform in size. I guess I do not see your point.

[rdt]: Now that it's resizable, reduce its size from the beginning value.  The Cancel button gets truncated!  A no-no!

[RLH]: I agree and disagree. I agree that truncating the buttons is a no-no. 
I disagree because the original change states that you could make the dialog "un-resizable" to prevent that, which is what I would do for a login dialog. So I was not thinking about resizing only aesthetics.

[rdt]: I understand.  If its made resizable in order that the entry boxes can be made larger, 
then the resizing should _never_ truncate a button. [RLH]: No argument from me there. 

[RS] 2004-09-14: Added a line each to unset ::_username and ::_password...

[LV] So what could be added to the second login to keep it from being resized so small that the buttons disappear?

[JJ] Added keybinding for <Escape> to both examples

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See also [Authentication by formula]
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[Tk] | [Arts and crafts of Tcl-Tk programming] | [Category Dialog] | [Category GUI]