PCNET 2006 September - Disc 1/PCNET_CD_2006_09.iso/linux/puppy-barebones-2.01r2.iso/pup_201.sfs/usr/lib/combobox-2.3/combobox.tcl

Text File | 2003-08-18 | 62.9 KB | 2,189 lines

# Copyright (c) 1998-2003, Bryan Oakley
# All Rights Reservered
#
# Bryan Oakley
# [e-mail]
#
# combobox v2.3 August 16, 2003
#
# a combobox / dropdown listbox (pick your favorite name) widget
# written in pure tcl
#
# this code is freely distributable without restriction, but is
# provided as-is with no warranty expressed or implied.
#
# thanks to the following people who provided beta test support or
# patches to the code (in no particular order):
#
# Scott Beasley     Alexandre Ferrieux      Todd Helfter
# Matt Gushee       Laurent Duperval        John Jackson
# Fred Rapp         Christopher Nelson
# Eric Galluzzo     Jean-Francois Moine        Oliver Bienert
#
# A special thanks to Martin M. Hunt who provided several good ideas,
# and always with a patch to implement them. Jean-Francois Moine,
# Todd Helfter and John Jackson were also kind enough to send in some
# code patches.
#
# ... and many others over the years.

package require Tk 8.0
package provide combobox 2.3

namespace eval ::combobox {

    # this is the public interface
    namespace export combobox

    # these contain references to available options
    variable widgetOptions

    # these contain references to available commands and subcommands
    variable widgetCommands
    variable scanCommands
    variable listCommands
}

# ::combobox::combobox --
#
#     This is the command that gets exported. It creates a new
#     combobox widget.
#
# Arguments:
#
#     w        path of new widget to create
#     args     additional option/value pairs (eg: -background white, etc.)
#
# Results:
#
#     It creates the widget and sets up all of the default bindings
#
# Returns:
#
#     The name of the newly create widget

proc ::combobox::combobox {w args} {
    variable widgetOptions
    variable widgetCommands
    variable scanCommands
    variable listCommands

    # perform a one time initialization
    if {![info exists widgetOptions]} {
    Init
    }

    # build it...
    eval Build $w $args

    # set some bindings...
    SetBindings $w

    # and we are done!
    return $w
}


# ::combobox::Init --
#
#     Initialize the namespace variables. This should only be called
#     once, immediately prior to creating the first instance of the
#     widget
#
# Arguments:
#
#    none
#
# Results:
#
#     All state variables are set to their default values; all of
#     the option database entries will exist.
#
# Returns:
#
#     empty string

proc ::combobox::Init {} {
    variable widgetOptions
    variable widgetCommands
    variable scanCommands
    variable listCommands
    variable defaultEntryCursor

    array set widgetOptions [list \
        -background          {background          Background} \
        -bd                  -borderwidth \
        -bg                  -background \
        -borderwidth         {borderWidth         BorderWidth} \
        -buttonbackground    {buttonBackground    Background} \
        -command             {command             Command} \
        -commandstate        {commandState        State} \
        -cursor              {cursor              Cursor} \
        -disabledbackground  {disabledBackground  DisabledBackground} \
        -disabledforeground  {disabledForeground  DisabledForeground} \
            -dropdownwidth       {dropdownWidth       DropdownWidth} \
        -editable            {editable            Editable} \
        -elementborderwidth  {elementBorderWidth  BorderWidth} \
        -fg                  -foreground \
        -font                {font                Font} \
        -foreground          {foreground          Foreground} \
        -height              {height              Height} \
        -highlightbackground {highlightBackground HighlightBackground} \
        -highlightcolor      {highlightColor      HighlightColor} \
        -highlightthickness  {highlightThickness  HighlightThickness} \
        -image               {image               Image} \
        -listvar             {listVariable        Variable} \
        -maxheight           {maxHeight           Height} \
        -opencommand         {opencommand         Command} \
        -relief              {relief              Relief} \
        -selectbackground    {selectBackground    Foreground} \
        -selectborderwidth   {selectBorderWidth   BorderWidth} \
        -selectforeground    {selectForeground    Background} \
        -state               {state               State} \
        -takefocus           {takeFocus           TakeFocus} \
        -textvariable        {textVariable        Variable} \
        -value               {value               Value} \
        -width               {width               Width} \
        -xscrollcommand      {xScrollCommand      ScrollCommand} \
    ]


    set widgetCommands [list \
        bbox      cget     configure    curselection \
        delete    get      icursor      index        \
        insert    list     scan         selection    \
        xview     select   toggle       open         \
            close    subwidget  \
    ]

    set listCommands [list \
        delete       get      \
            index        insert       size \
    ]

    set scanCommands [list mark dragto]

    # why check for the Tk package? This lets us be sourced into
    # an interpreter that doesn't have Tk loaded, such as the slave
    # interpreter used by pkg_mkIndex. In theory it should have no
    # side effects when run
    if {[lsearch -exact [package names] "Tk"] != -1} {

    ##################################################################
    #- this initializes the option database. Kinda gross, but it works
    #- (I think).
    ##################################################################

    # the image used for the button...
    if {$::tcl_platform(platform) == "windows"} {
        image create bitmap ::combobox::bimage -data {
        #define down_arrow_width 12
        #define down_arrow_height 12
        static char down_arrow_bits[] = {
            0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
            0xfc,0xf1,0xf8,0xf0,0x70,0xf0,0x20,0xf0,
            0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00;
        }
        }
    } else {
        image create bitmap ::combobox::bimage -data  {
        #define down_arrow_width 15
        #define down_arrow_height 15
        static char down_arrow_bits[] = {
            0x00,0x80,0x00,0x80,0x00,0x80,0x00,0x80,
            0x00,0x80,0xf8,0x8f,0xf0,0x87,0xe0,0x83,
            0xc0,0x81,0x80,0x80,0x00,0x80,0x00,0x80,
            0x00,0x80,0x00,0x80,0x00,0x80
        }
        }
    }

    # compute a widget name we can use to create a temporary widget
    set tmpWidget ".__tmp__"
    set count 0
    while {[winfo exists $tmpWidget] == 1} {
        set tmpWidget ".__tmp__$count"
        incr count
    }

    # get the scrollbar width. Because we try to be clever and draw our
    # own button instead of using a tk widget, we need to know what size
    # button to create. This little hack tells us the width of a scroll
    # bar.
    #
    # NB: we need to be sure and pick a window  that doesn't already
    # exist...
    scrollbar $tmpWidget
    set sb_width [winfo reqwidth $tmpWidget]
    set bbg [$tmpWidget cget -background]
    destroy $tmpWidget

    # steal options from the entry widget
    # we want darn near all options, so we'll go ahead and do
    # them all. No harm done in adding the one or two that we
    # don't use.
    entry $tmpWidget
    foreach foo [$tmpWidget configure] {
        # the cursor option is special, so we'll save it in
        # a special way
        if {[lindex $foo 0] == "-cursor"} {
        set defaultEntryCursor [lindex $foo 4]
        }
        if {[llength $foo] == 5} {
        set option [lindex $foo 1]
        set value [lindex $foo 4]
        option add *Combobox.$option $value widgetDefault

        # these options also apply to the dropdown listbox
        if {[string compare $option "foreground"] == 0 \
            || [string compare $option "background"] == 0 \
            || [string compare $option "font"] == 0} {
            option add *Combobox*ComboboxListbox.$option $value \
                widgetDefault
        }
        }
    }
    destroy $tmpWidget

    # these are unique to us...
    option add *Combobox.elementBorderWidth  1    widgetDefault
    option add *Combobox.buttonBackground    $bbg    widgetDefault
    option add *Combobox.dropdownWidth       {}     widgetDefault
    option add *Combobox.openCommand         {}     widgetDefault
    option add *Combobox.cursor              {}     widgetDefault
    option add *Combobox.commandState        normal widgetDefault
    option add *Combobox.editable            1      widgetDefault
    option add *Combobox.maxHeight           10     widgetDefault
    option add *Combobox.height              0
    }

    # set class bindings
    SetClassBindings
}

# ::combobox::SetClassBindings --
#
#    Sets up the default bindings for the widget class
#
#    this proc exists since it's The Right Thing To Do, but
#    I haven't had the time to figure out how to do all the
#    binding stuff on a class level. The main problem is that
#    the entry widget must have focus for the insertion cursor
#    to be visible. So, I either have to have the entry widget
#    have the Combobox bindtag, or do some fancy juggling of
#    events or some such. What a pain.
#
# Arguments:
#
#    none
#
# Returns:
#
#    empty string

proc ::combobox::SetClassBindings {} {

    # make sure we clean up after ourselves...
    bind Combobox <Destroy> [list ::combobox::DestroyHandler %W]

    # this will (hopefully) close (and lose the grab on) the
    # listbox if the user clicks anywhere outside of it. Note
    # that on Windows, you can click on some other app and
    # the listbox will still be there, because tcl won't see
    # that button click
    set this {[::combobox::convert %W -W]}
    bind Combobox <Any-ButtonPress>   "$this close"
    bind Combobox <Any-ButtonRelease> "$this close"

    # this helps (but doesn't fully solve) focus issues. The general
    # idea is, whenever the frame gets focus it gets passed on to
    # the entry widget
    bind Combobox <FocusIn> {::combobox::tkTabToWindow \
                 [::combobox::convert %W -W].entry}

    # this closes the listbox if we get hidden
    bind Combobox <Unmap> {[::combobox::convert %W -W] close}

    return ""
}

# ::combobox::SetBindings --
#
#    here's where we do most of the binding foo. I think there's probably
#    a few bindings I ought to add that I just haven't thought
#    about...
#
#    I'm not convinced these are the proper bindings. Ideally all
#    bindings should be on "Combobox", but because of my juggling of
#    bindtags I'm not convinced thats what I want to do. But, it all
#    seems to work, its just not as robust as it could be.
#
# Arguments:
#
#    w    widget pathname
#
# Returns:
#
#    empty string

proc ::combobox::SetBindings {w} {
    upvar ::combobox::${w}::widgets  widgets
    upvar ::combobox::${w}::options  options

    # juggle the bindtags. The basic idea here is to associate the
    # widget name with the entry widget, so if a user does a bind
    # on the combobox it will get handled properly since it is
    # the entry widget that has keyboard focus.
    bindtags $widgets(entry) \
        [concat $widgets(this) [bindtags $widgets(entry)]]

    bindtags $widgets(button) \
        [concat $widgets(this) [bindtags $widgets(button)]]

    # override the default bindings for tab and shift-tab. The
    # focus procs take a widget as their only parameter and we
    # want to make sure the right window gets used (for shift-
    # tab we want it to appear as if the event was generated
    # on the frame rather than the entry.
    bind $widgets(entry) <Tab> \
        "::combobox::tkTabToWindow \[tk_focusNext $widgets(entry)\]; break"
    bind $widgets(entry) <Shift-Tab> \
        "::combobox::tkTabToWindow \[tk_focusPrev $widgets(this)\]; break"

    # this makes our "button" (which is actually a label)
    # do the right thing
    bind $widgets(button) <ButtonPress-1> [list $widgets(this) toggle]

    # this lets the autoscan of the listbox work, even if they
    # move the cursor over the entry widget.
    bind $widgets(entry) <B1-Enter> "break"

    bind $widgets(listbox) <ButtonRelease-1> \
        "::combobox::Select [list $widgets(this)] \
         \[$widgets(listbox) nearest %y\]; break"

    bind $widgets(vsb) <ButtonPress-1>   {continue}
    bind $widgets(vsb) <ButtonRelease-1> {continue}

    bind $widgets(listbox) <Any-Motion> {
    %W selection clear 0 end
    %W activate @%x,%y
    %W selection anchor @%x,%y
    %W selection set @%x,%y @%x,%y
    # need to do a yview if the cursor goes off the top
    # or bottom of the window... (or do we?)
    }

    # these events need to be passed from the entry widget
    # to the listbox, or otherwise need some sort of special
    # handling.
    foreach event [list <Up> <Down> <Tab> <Return> <Escape> \
        <Next> <Prior> <Double-1> <1> <Any-KeyPress> \
        <FocusIn> <FocusOut>] {
    bind $widgets(entry) $event \
            [list ::combobox::HandleEvent $widgets(this) $event]
    }

    # like the other events, <MouseWheel> needs to be passed from
    # the entry widget to the listbox. However, in this case we
    # need to add an additional parameter
    catch {
    bind $widgets(entry) <MouseWheel> \
        [list ::combobox::HandleEvent $widgets(this) <MouseWheel> %D]
    }
}

# ::combobox::Build --
#
#    This does all of the work necessary to create the basic
#    combobox.
#
# Arguments:
#
#    w        widget name
#    args     additional option/value pairs
#
# Results:
#
#    Creates a new widget with the given name. Also creates a new
#    namespace patterened after the widget name, as a child namespace
#    to ::combobox
#
# Returns:
#
#    the name of the widget

proc ::combobox::Build {w args } {
    variable widgetOptions

    if {[winfo exists $w]} {
    error "window name \"$w\" already exists"
    }

    # create the namespace for this instance, and define a few
    # variables
    namespace eval ::combobox::$w {

    variable ignoreTrace 0
    variable oldFocus    {}
    variable oldGrab     {}
    variable oldValue    {}
    variable options
    variable this
    variable widgets

    set widgets(foo) foo  ;# coerce into an array
    set options(foo) foo  ;# coerce into an array

    unset widgets(foo)
    unset options(foo)
    }

    # import the widgets and options arrays into this proc so
    # we don't have to use fully qualified names, which is a
    # pain.
    upvar ::combobox::${w}::widgets widgets
    upvar ::combobox::${w}::options options

    # this is our widget -- a frame of class Combobox. Naturally,
    # it will contain other widgets. We create it here because
    # we need it in order to set some default options.
    set widgets(this)   [frame  $w -class Combobox -takefocus 0]
    set widgets(entry)  [entry  $w.entry -takefocus 1]
    set widgets(button) [label  $w.button -takefocus 0]

    # this defines all of the default options. We get the
    # values from the option database. Note that if an array
    # value is a list of length one it is an alias to another
    # option, so we just ignore it
    foreach name [array names widgetOptions] {
    if {[llength $widgetOptions($name)] == 1} continue

    set optName  [lindex $widgetOptions($name) 0]
    set optClass [lindex $widgetOptions($name) 1]

    set value [option get $w $optName $optClass]
    set options($name) $value
    }

    # a couple options aren't available in earlier versions of
    # tcl, so we'll set them to sane values. For that matter, if
    # they exist but are empty, set them to sane values.
    if {[string length $options(-disabledforeground)] == 0} {
        set options(-disabledforeground) $options(-foreground)
    }
    if {[string length $options(-disabledbackground)] == 0} {
        set options(-disabledbackground) $options(-background)
    }

    # if -value is set to null, we'll remove it from our
    # local array. The assumption is, if the user sets it from
    # the option database, they will set it to something other
    # than null (since it's impossible to determine the difference
    # between a null value and no value at all).
    if {[info exists options(-value)] \
        && [string length $options(-value)] == 0} {
    unset options(-value)
    }

    # we will later rename the frame's widget proc to be our
    # own custom widget proc. We need to keep track of this
    # new name, so we'll define and store it here...
    set widgets(frame) ::combobox::${w}::$w

    # gotta do this sooner or later. Might as well do it now
    pack $widgets(button) -side right -fill y    -expand no
    pack $widgets(entry)  -side left  -fill both -expand yes

    # I should probably do this in a catch, but for now it's
    # good enough... What it does, obviously, is put all of
    # the option/values pairs into an array. Make them easier
    # to handle later on...
    array set options $args

    # now, the dropdown list... the same renaming nonsense
    # must go on here as well...
    set widgets(dropdown)   [toplevel  $w.top]
    set widgets(listbox) [listbox   $w.top.list]
    set widgets(vsb)     [scrollbar $w.top.vsb]

    pack $widgets(listbox) -side left -fill both -expand y

    # fine tune the widgets based on the options (and a few
    # arbitrary values...)

    # NB: we are going to use the frame to handle the relief
    # of the widget as a whole, so the entry widget will be
    # flat. This makes the button which drops down the list
    # to appear "inside" the entry widget.

    $widgets(vsb) configure \
        -borderwidth 1 \
        -command "$widgets(listbox) yview" \
        -highlightthickness 0

    $widgets(button) configure \
        -background $options(-buttonbackground) \
        -highlightthickness 0 \
        -borderwidth $options(-elementborderwidth) \
        -relief raised \
        -width [expr {[winfo reqwidth $widgets(vsb)] - 2}]

    $widgets(entry) configure \
        -borderwidth 0 \
        -relief flat \
        -highlightthickness 0

    $widgets(dropdown) configure \
        -borderwidth $options(-elementborderwidth) \
        -relief sunken

    $widgets(listbox) configure \
        -selectmode browse \
        -background [$widgets(entry) cget -bg] \
        -yscrollcommand "$widgets(vsb) set" \
        -exportselection false \
        -borderwidth 0


#    trace variable ::combobox::${w}::entryTextVariable w \
#        [list ::combobox::EntryTrace $w]

    # do some window management foo on the dropdown window
    wm overrideredirect $widgets(dropdown) 1
    wm transient        $widgets(dropdown) [winfo toplevel $w]
    wm group            $widgets(dropdown) [winfo parent $w]
    wm resizable        $widgets(dropdown) 0 0
    wm withdraw         $widgets(dropdown)

    # this moves the original frame widget proc into our
    # namespace and gives it a handy name
    rename ::$w $widgets(frame)

    # now, create our widget proc. Obviously (?) it goes in
    # the global namespace. All combobox widgets will actually
    # share the same widget proc to cut down on the amount of
    # bloat.
    proc ::$w {command args} \
        "eval ::combobox::WidgetProc $w \$command \$args"


    # ok, the thing exists... let's do a bit more configuration.
    if {[catch "::combobox::Configure [list $widgets(this)] [array get options]" error]} {
    catch {destroy $w}
    error "internal error: $error"
    }

    return ""

}

# ::combobox::HandleEvent --
#
#    this proc handles events from the entry widget that we want
#    handled specially (typically, to allow navigation of the list
#    even though the focus is in the entry widget)
#
# Arguments:
#
#    w       widget pathname
#    event   a string representing the event (not necessarily an
#            actual event)
#    args    additional arguments required by particular events

proc ::combobox::HandleEvent {w event args} {
    upvar ::combobox::${w}::widgets  widgets
    upvar ::combobox::${w}::options  options
    upvar ::combobox::${w}::oldValue oldValue

    # for all of these events, if we have a special action we'll
    # do that and do a "return -code break" to keep additional
    # bindings from firing. Otherwise we'll let the event fall
    # on through.
    switch $event {

        "<MouseWheel>" {
        if {[winfo ismapped $widgets(dropdown)]} {
                set D [lindex $args 0]
                # the '120' number in the following expression has
                # it's genesis in the tk bind manpage, which suggests
                # that the smallest value of %D for mousewheel events
                # will be 120. The intent is to scroll one line at a time.
                $widgets(listbox) yview scroll [expr {-($D/120)}] units
            }
        }

    "<Any-KeyPress>" {
        # if the widget is editable, clear the selection.
        # this makes it more obvious what will happen if the
        # user presses <Return> (and helps our code know what
        # to do if the user presses return)
        if {$options(-editable)} {
        $widgets(listbox) see 0
        $widgets(listbox) selection clear 0 end
        $widgets(listbox) selection anchor 0
        $widgets(listbox) activate 0
        }
    }

    "<FocusIn>" {
        set oldValue [$widgets(entry) get]
    }

    "<FocusOut>" {
        if {![winfo ismapped $widgets(dropdown)]} {
        # did the value change?
        set newValue [$widgets(entry) get]
        if {$oldValue != $newValue} {
            CallCommand $widgets(this) $newValue
        }
        }
    }

    "<1>" {
        set editable [::combobox::GetBoolean $options(-editable)]
        if {!$editable} {
        if {[winfo ismapped $widgets(dropdown)]} {
            $widgets(this) close
            return -code break;

        } else {
            if {$options(-state) != "disabled"} {
            $widgets(this) open
            return -code break;
            }
        }
        }
    }

    "<Double-1>" {
        if {$options(-state) != "disabled"} {
        $widgets(this) toggle
        return -code break;
        }
    }

    "<Tab>" {
        if {[winfo ismapped $widgets(dropdown)]} {
        ::combobox::Find $widgets(this) 0
        return -code break;
        } else {
        ::combobox::SetValue $widgets(this) [$widgets(this) get]
        }
    }

    "<Escape>" {
#        $widgets(entry) delete 0 end
#        $widgets(entry) insert 0 $oldValue
        if {[winfo ismapped $widgets(dropdown)]} {
        $widgets(this) close
        return -code break;
        }
    }

    "<Return>" {
        # did the value change?
        set newValue [$widgets(entry) get]
        if {$oldValue != $newValue} {
        CallCommand $widgets(this) $newValue
        }

        if {[winfo ismapped $widgets(dropdown)]} {
        ::combobox::Select $widgets(this) \
            [$widgets(listbox) curselection]
        return -code break;
        }

    }

    "<Next>" {
        $widgets(listbox) yview scroll 1 pages
        set index [$widgets(listbox) index @0,0]
        $widgets(listbox) see $index
        $widgets(listbox) activate $index
        $widgets(listbox) selection clear 0 end
        $widgets(listbox) selection anchor $index
        $widgets(listbox) selection set $index

    }

    "<Prior>" {
        $widgets(listbox) yview scroll -1 pages
        set index [$widgets(listbox) index @0,0]
        $widgets(listbox) activate $index
        $widgets(listbox) see $index
        $widgets(listbox) selection clear 0 end
        $widgets(listbox) selection anchor $index
        $widgets(listbox) selection set $index
    }

    "<Down>" {
        if {[winfo ismapped $widgets(dropdown)]} {
        ::combobox::tkListboxUpDown $widgets(listbox) 1
        return -code break;

        } else {
        if {$options(-state) != "disabled"} {
            $widgets(this) open
            return -code break;
        }
        }
    }
    "<Up>" {
        if {[winfo ismapped $widgets(dropdown)]} {
        ::combobox::tkListboxUpDown $widgets(listbox) -1
        return -code break;

        } else {
        if {$options(-state) != "disabled"} {
            $widgets(this) open
            return -code break;
        }
        }
    }
    }

    return ""
}

# ::combobox::DestroyHandler {w} --
#
#    Cleans up after a combobox widget is destroyed
#
# Arguments:
#
#    w    widget pathname
#
# Results:
#
#    The namespace that was created for the widget is deleted,
#    and the widget proc is removed.

proc ::combobox::DestroyHandler {w} {

    catch {
    # if the widget actually being destroyed is of class Combobox,
    # remove the namespace and associated proc.
    if {[string compare [winfo class $w] "Combobox"] == 0} {
        # delete the namespace and the proc which represents
        # our widget
        namespace delete ::combobox::$w
        rename $w {}
    }
    }
    return ""
}

# ::combobox::Find
#
#    finds something in the listbox that matches the pattern in the
#    entry widget and selects it
#
#    N.B. I'm not convinced this is working the way it ought to. It
#    works, but is the behavior what is expected? I've also got a gut
#    feeling that there's a better way to do this, but I'm too lazy to
#    figure it out...
#
# Arguments:
#
#    w      widget pathname
#    exact  boolean; if true an exact match is desired
#
# Returns:
#
#    Empty string

proc ::combobox::Find {w {exact 0}} {
    upvar ::combobox::${w}::widgets widgets
    upvar ::combobox::${w}::options options

    ## *sigh* this logic is rather gross and convoluted. Surely
    ## there is a more simple, straight-forward way to implement
    ## all this. As the saying goes, I lack the time to make it
    ## shorter...

    # use what is already in the entry widget as a pattern
    set pattern [$widgets(entry) get]

    if {[string length $pattern] == 0} {
    # clear the current selection
    $widgets(listbox) see 0
    $widgets(listbox) selection clear 0 end
    $widgets(listbox) selection anchor 0
    $widgets(listbox) activate 0
    return
    }

    # we're going to be searching this list...
    set list [$widgets(listbox) get 0 end]

    # if we are doing an exact match, try to find,
    # well, an exact match
    set exactMatch -1
    if {$exact} {
    set exactMatch [lsearch -exact $list $pattern]
    }

    # search for it. We'll try to be clever and not only
    # search for a match for what they typed, but a match for
    # something close to what they typed. We'll keep removing one
    # character at a time from the pattern until we find a match
    # of some sort.
    set index -1
    while {$index == -1 && [string length $pattern]} {
    set index [lsearch -glob $list "$pattern*"]
    if {$index == -1} {
        regsub {.$} $pattern {} pattern
    }
    }

    # this is the item that most closely matches...
    set thisItem [lindex $list $index]

    # did we find a match? If so, do some additional munging...
    if {$index != -1} {

    # we need to find the part of the first item that is
    # unique WRT the second... I know there's probably a
    # simpler way to do this...

    set nextIndex [expr {$index + 1}]
    set nextItem [lindex $list $nextIndex]

    # we don't really need to do much if the next
    # item doesn't match our pattern...
    if {[string match $pattern* $nextItem]} {
        # ok, the next item matches our pattern, too
        # now the trick is to find the first character
        # where they *don't* match...
        set marker [string length $pattern]
        while {$marker <= [string length $pattern]} {
        set a [string index $thisItem $marker]
        set b [string index $nextItem $marker]
        if {[string compare $a $b] == 0} {
            append pattern $a
            incr marker
        } else {
            break
        }
        }
    } else {
        set marker [string length $pattern]
    }

    } else {
    set marker end
    set index 0
    }

    # ok, we know the pattern and what part is unique;
    # update the entry widget and listbox appropriately
    if {$exact && $exactMatch == -1} {
    # this means we didn't find an exact match
    $widgets(listbox) selection clear 0 end
    $widgets(listbox) see $index

    } elseif {!$exact}  {
    # this means we found something, but it isn't an exact
    # match. If we find something that *is* an exact match we
    # don't need to do the following, since it would merely
    # be replacing the data in the entry widget with itself
    set oldstate [$widgets(entry) cget -state]
    $widgets(entry) configure -state normal
    $widgets(entry) delete 0 end
    $widgets(entry) insert end $thisItem
    $widgets(entry) selection clear
    $widgets(entry) selection range $marker end
    $widgets(listbox) activate $index
    $widgets(listbox) selection clear 0 end
    $widgets(listbox) selection anchor $index
    $widgets(listbox) selection set $index
    $widgets(listbox) see $index
    $widgets(entry) configure -state $oldstate
    }
}

# ::combobox::Select --
#
#    selects an item from the list and sets the value of the combobox
#    to that value
#
# Arguments:
#
#    w      widget pathname
#    index  listbox index of item to be selected
#
# Returns:
#
#    empty string

proc ::combobox::Select {w index} {
    upvar ::combobox::${w}::widgets widgets
    upvar ::combobox::${w}::options options

    # the catch is because I'm sloppy -- presumably, the only time
    # an error will be caught is if there is no selection.
    if {![catch {set data [$widgets(listbox) get [lindex $index 0]]}]} {
    ::combobox::SetValue $widgets(this) $data

    $widgets(listbox) selection clear 0 end
    $widgets(listbox) selection anchor $index
    $widgets(listbox) selection set $index

    }
    $widgets(entry) selection range 0 end
    $widgets(entry) icursor end

    $widgets(this) close

    return ""
}

# ::combobox::HandleScrollbar --
#
#    causes the scrollbar of the dropdown list to appear or disappear
#    based on the contents of the dropdown listbox
#
# Arguments:
#
#    w       widget pathname
#    action  the action to perform on the scrollbar
#
# Returns:
#
#    an empty string

proc ::combobox::HandleScrollbar {w {action "unknown"}} {
    upvar ::combobox::${w}::widgets widgets
    upvar ::combobox::${w}::options options

    if {$options(-height) == 0} {
    set hlimit $options(-maxheight)
    } else {
    set hlimit $options(-height)
    }

    switch $action {
    "grow" {
        if {$hlimit > 0 && [$widgets(listbox) size] > $hlimit} {
        pack forget $widgets(listbox)
        pack $widgets(vsb) -side right -fill y -expand n
        pack $widgets(listbox) -side left -fill both -expand y
        }
    }

    "shrink" {
        if {$hlimit > 0 && [$widgets(listbox) size] <= $hlimit} {
        pack forget $widgets(vsb)
        }
    }

    "crop" {
        # this means the window was cropped and we definitely
        # need a scrollbar no matter what the user wants
        pack forget $widgets(listbox)
        pack $widgets(vsb) -side right -fill y -expand n
        pack $widgets(listbox) -side left -fill both -expand y
    }

    default {
        if {$hlimit > 0 && [$widgets(listbox) size] > $hlimit} {
        pack forget $widgets(listbox)
        pack $widgets(vsb) -side right -fill y -expand n
        pack $widgets(listbox) -side left -fill both -expand y
        } else {
        pack forget $widgets(vsb)
        }
    }
    }

    return ""
}

# ::combobox::ComputeGeometry --
#
#    computes the geometry of the dropdown list based on the size of the
#    combobox...
#
# Arguments:
#
#    w     widget pathname
#
# Returns:
#
#    the desired geometry of the listbox

proc ::combobox::ComputeGeometry {w} {
    upvar ::combobox::${w}::widgets widgets
    upvar ::combobox::${w}::options options

    if {$options(-height) == 0 && $options(-maxheight) != "0"} {
    # if this is the case, count the items and see if
    # it exceeds our maxheight. If so, set the listbox
    # size to maxheight...
    set nitems [$widgets(listbox) size]
    if {$nitems > $options(-maxheight)} {
        # tweak the height of the listbox
        $widgets(listbox) configure -height $options(-maxheight)
    } else {
        # un-tweak the height of the listbox
        $widgets(listbox) configure -height 0
    }
    update idletasks
    }

    # compute height and width of the dropdown list
    set bd [$widgets(dropdown) cget -borderwidth]
    set height [expr {[winfo reqheight $widgets(dropdown)] + $bd + $bd}]
    if {[string length $options(-dropdownwidth)] == 0 ||
        $options(-dropdownwidth) == 0} {
        set width [winfo width $widgets(this)]
    } else {
        set m [font measure [$widgets(listbox) cget -font] "m"]
        set width [expr {$options(-dropdownwidth) * $m}]
    }

    # figure out where to place it on the screen, trying to take into
    # account we may be running under some virtual window manager
    set screenWidth  [winfo screenwidth $widgets(this)]
    set screenHeight [winfo screenheight $widgets(this)]
    set rootx        [winfo rootx $widgets(this)]
    set rooty        [winfo rooty $widgets(this)]
    set vrootx       [winfo vrootx $widgets(this)]
    set vrooty       [winfo vrooty $widgets(this)]

    # the x coordinate is simply the rootx of our widget, adjusted for
    # the virtual window. We won't worry about whether the window will
    # be offscreen to the left or right -- we want the illusion that it
    # is part of the entry widget, so if part of the entry widget is off-
    # screen, so will the list. If you want to change the behavior,
    # simply change the if statement... (and be sure to update this
    # comment!)
    set x  [expr {$rootx + $vrootx}]
    if {0} {
    set rightEdge [expr {$x + $width}]
    if {$rightEdge > $screenWidth} {
        set x [expr {$screenWidth - $width}]
    }
    if {$x < 0} {set x 0}
    }

    # the y coordinate is the rooty plus vrooty offset plus
    # the height of the static part of the widget plus 1 for a
    # tiny bit of visual separation...
    set y [expr {$rooty + $vrooty + [winfo reqheight $widgets(this)] + 1}]
    set bottomEdge [expr {$y + $height}]

    if {$bottomEdge >= $screenHeight} {
    # ok. Fine. Pop it up above the entry widget isntead of
    # below.
    set y [expr {($rooty - $height - 1) + $vrooty}]

    if {$y < 0} {
        # this means it extends beyond our screen. How annoying.
        # Now we'll try to be real clever and either pop it up or
        # down, depending on which way gives us the biggest list.
        # then, we'll trim the list to fit and force the use of
        # a scrollbar

        # (sadly, for windows users this measurement doesn't
        # take into consideration the height of the taskbar,
        # but don't blame me -- there isn't any way to detect
        # it or figure out its dimensions. The same probably
        # applies to any window manager with some magic windows
        # glued to the top or bottom of the screen)

        if {$rooty > [expr {$screenHeight / 2}]} {
        # we are in the lower half of the screen --
        # pop it up. Y is zero; that parts easy. The height
        # is simply the y coordinate of our widget, minus
        # a pixel for some visual separation. The y coordinate
        # will be the topof the screen.
        set y 1
        set height [expr {$rooty - 1 - $y}]

        } else {
        # we are in the upper half of the screen --
        # pop it down
        set y [expr {$rooty + $vrooty + \
            [winfo reqheight $widgets(this)] + 1}]
        set height [expr {$screenHeight - $y}]

        }

        # force a scrollbar
        HandleScrollbar $widgets(this) crop
    }
    }

    if {$y < 0} {
    # hmmm. Bummer.
    set y 0
    set height $screenheight
    }

    set geometry [format "=%dx%d+%d+%d" $width $height $x $y]

    return $geometry
}

# ::combobox::DoInternalWidgetCommand --
#
#    perform an internal widget command, then mung any error results
#    to look like it came from our megawidget. A lot of work just to
#    give the illusion that our megawidget is an atomic widget
#
# Arguments:
#
#    w           widget pathname
#    subwidget   pathname of the subwidget
#    command     subwidget command to be executed
#    args        arguments to the command
#
# Returns:
#
#    The result of the subwidget command, or an error

proc ::combobox::DoInternalWidgetCommand {w subwidget command args} {
    upvar ::combobox::${w}::widgets widgets
    upvar ::combobox::${w}::options options

    set subcommand $command
    set command [concat $widgets($subwidget) $command $args]
    if {[catch $command result]} {
    # replace the subwidget name with the megawidget name
    regsub $widgets($subwidget) $result $widgets(this) result

    # replace specific instances of the subwidget command
    # with our megawidget command
    switch $subwidget,$subcommand {
        listbox,index  {regsub "index"  $result "list index"  result}
        listbox,insert {regsub "insert" $result "list insert" result}
        listbox,delete {regsub "delete" $result "list delete" result}
        listbox,get    {regsub "get"    $result "list get"    result}
        listbox,size   {regsub "size"   $result "list size"   result}
    }
    error $result

    } else {
    return $result
    }
}


# ::combobox::WidgetProc --
#
#    This gets uses as the widgetproc for an combobox widget.
#    Notice where the widget is created and you'll see that the
#    actual widget proc merely evals this proc with all of the
#    arguments intact.
#
#    Note that some widget commands are defined "inline" (ie:
#    within this proc), and some do most of their work in
#    separate procs. This is merely because sometimes it was
#    easier to do it one way or the other.
#
# Arguments:
#
#    w         widget pathname
#    command   widget subcommand
#    args      additional arguments; varies with the subcommand
#
# Results:
#
#    Performs the requested widget command

proc ::combobox::WidgetProc {w command args} {
    upvar ::combobox::${w}::widgets widgets
    upvar ::combobox::${w}::options options
    upvar ::combobox::${w}::oldFocus oldFocus
    upvar ::combobox::${w}::oldFocus oldGrab

    set command [::combobox::Canonize $w command $command]

    # this is just shorthand notation...
    set doWidgetCommand \
        [list ::combobox::DoInternalWidgetCommand $widgets(this)]

    if {$command == "list"} {
    # ok, the next argument is a list command; we'll
    # rip it from args and append it to command to
    # create a unique internal command
    #
    # NB: because of the sloppy way we are doing this,
    # we'll also let the user enter our secret command
    # directly (eg: listinsert, listdelete), but we
    # won't document that fact
    set command "list-[lindex $args 0]"
    set args [lrange $args 1 end]
    }

    set result ""

    # many of these commands are just synonyms for specific
    # commands in one of the subwidgets. We'll get them out
    # of the way first, then do the custom commands.
    switch $command {
    bbox -
    delete -
    get -
    icursor -
    index -
    insert -
    scan -
    selection -
    xview {
        set result [eval $doWidgetCommand entry $command $args]
    }
    list-get     {set result [eval $doWidgetCommand listbox get $args]}
    list-index     {set result [eval $doWidgetCommand listbox index $args]}
    list-size     {set result [eval $doWidgetCommand listbox size $args]}

    select {
        if {[llength $args] == 1} {
        set index [lindex $args 0]
        set result [Select $widgets(this) $index]
        } else {
        error "usage: $w select index"
        }
    }

    subwidget {
        set knownWidgets [list button entry listbox dropdown vsb]
        if {[llength $args] == 0} {
        return $knownWidgets
        }

        set name [lindex $args 0]
        if {[lsearch $knownWidgets $name] != -1} {
        set result $widgets($name)
        } else {
        error "unknown subwidget $name"
        }
    }

    curselection {
        set result [eval $doWidgetCommand listbox curselection]
    }

    list-insert {
        eval $doWidgetCommand listbox insert $args
        set result [HandleScrollbar $w "grow"]
    }

    list-delete {
        eval $doWidgetCommand listbox delete $args
        set result [HandleScrollbar $w "shrink"]
    }

    toggle {
        # ignore this command if the widget is disabled...
        if {$options(-state) == "disabled"} return

        # pops down the list if it is not, hides it
        # if it is...
        if {[winfo ismapped $widgets(dropdown)]} {
        set result [$widgets(this) close]
        } else {
        set result [$widgets(this) open]
        }
    }

    open {

        # if this is an editable combobox, the focus should
        # be set to the entry widget
        if {$options(-editable)} {
        focus $widgets(entry)
        $widgets(entry) select range 0 end
        $widgets(entry) icursor end
        }

        # if we are disabled, we won't allow this to happen
        if {$options(-state) == "disabled"} {
        return 0
        }

        # if there is a -opencommand, execute it now
        if {[string length $options(-opencommand)] > 0} {
        # hmmm... should I do a catch, or just let the normal
        # error handling handle any errors? For now, the latter...
        uplevel \#0 $options(-opencommand)
        }

        # compute the geometry of the window to pop up, and set
        # it, and force the window manager to take notice
        # (even if it is not presently visible).
        #
        # this isn't strictly necessary if the window is already
        # mapped, but we'll go ahead and set the geometry here
        # since its harmless and *may* actually reset the geometry
        # to something better in some weird case.
        set geometry [::combobox::ComputeGeometry $widgets(this)]
        wm geometry $widgets(dropdown) $geometry
        update idletasks

        # if we are already open, there's nothing else to do
        if {[winfo ismapped $widgets(dropdown)]} {
        return 0
        }

        # save the widget that currently has the focus; we'll restore
        # the focus there when we're done
        set oldFocus [focus]

        # ok, tweak the visual appearance of things and
        # make the list pop up
        $widgets(button) configure -relief sunken
        wm deiconify $widgets(dropdown)
        update idletasks
        raise $widgets(dropdown)

        # force focus to the entry widget so we can handle keypress
        # events for traversal
        focus -force $widgets(entry)

        # select something by default, but only if its an
        # exact match...
        ::combobox::Find $widgets(this) 1

        # save the current grab state for the display containing
        # this widget. We'll restore it when we close the dropdown
        # list
        set status "none"
        set grab [grab current $widgets(this)]
        if {$grab != ""} {set status [grab status $grab]}
        set oldGrab [list $grab $status]
        unset grab status

        # *gasp* do a global grab!!! Mom always told me not to
        # do things like this, but sometimes a man's gotta do
        # what a man's gotta do.
        grab -global $widgets(this)

        # fake the listbox into thinking it has focus. This is
        # necessary to get scanning initialized properly in the
        # listbox.
        event generate $widgets(listbox) <B1-Enter>

        return 1
    }

    close {
        # if we are already closed, don't do anything...
        if {![winfo ismapped $widgets(dropdown)]} {
        return 0
        }

        # restore the focus and grab, but ignore any errors...
        # we're going to be paranoid and release the grab before
        # trying to set any other grab because we really really
        # really want to make sure the grab is released.
        catch {focus $oldFocus} result
        catch {grab release $widgets(this)}
        catch {
        set status [lindex $oldGrab 1]
        if {$status == "global"} {
            grab -global [lindex $oldGrab 0]
        } elseif {$status == "local"} {
            grab [lindex $oldGrab 0]
        }
        unset status
        }

        # hides the listbox
        $widgets(button) configure -relief raised
        wm withdraw $widgets(dropdown)

        # select the data in the entry widget. Not sure
        # why, other than observation seems to suggest that's
        # what windows widgets do.
        set editable [::combobox::GetBoolean $options(-editable)]
        if {$editable} {
        $widgets(entry) selection range 0 end
        $widgets(button) configure -relief raised
        }


        # magic tcl stuff (see tk.tcl in the distribution
        # lib directory)
        ::combobox::tkCancelRepeat

        return 1
    }

    cget {
        if {[llength $args] != 1} {
        error "wrong # args: should be $w cget option"
        }
        set opt [::combobox::Canonize $w option [lindex $args 0]]

        if {$opt == "-value"} {
        set result [$widgets(entry) get]
        } else {
        set result $options($opt)
        }
    }

    configure {
        set result [eval ::combobox::Configure {$w} $args]
    }

    default {
        error "bad option \"$command\""
    }
    }

    return $result
}

# ::combobox::Configure --
#
#    Implements the "configure" widget subcommand
#
# Arguments:
#
#    w      widget pathname
#    args   zero or more option/value pairs (or a single option)
#
# Results:
#
#    Performs typcial "configure" type requests on the widget

proc ::combobox::Configure {w args} {
    variable widgetOptions
    variable defaultEntryCursor

    upvar ::combobox::${w}::widgets widgets
    upvar ::combobox::${w}::options options

    if {[llength $args] == 0} {
    # hmmm. User must be wanting all configuration information
    # note that if the value of an array element is of length
    # one it is an alias, which needs to be handled slightly
    # differently
    set results {}
    foreach opt [lsort [array names widgetOptions]] {
        if {[llength $widgetOptions($opt)] == 1} {
        set alias $widgetOptions($opt)
        set optName $widgetOptions($alias)
        lappend results [list $opt $optName]
        } else {
        set optName  [lindex $widgetOptions($opt) 0]
        set optClass [lindex $widgetOptions($opt) 1]
        set default [option get $w $optName $optClass]
        if {[info exists options($opt)]} {
            lappend results [list $opt $optName $optClass \
                $default $options($opt)]
        } else {
            lappend results [list $opt $optName $optClass \
                $default ""]
        }
        }
    }

    return $results
    }

    # one argument means we are looking for configuration
    # information on a single option
    if {[llength $args] == 1} {
    set opt [::combobox::Canonize $w option [lindex $args 0]]

    set optName  [lindex $widgetOptions($opt) 0]
    set optClass [lindex $widgetOptions($opt) 1]
    set default [option get $w $optName $optClass]
    set results [list $opt $optName $optClass \
        $default $options($opt)]
    return $results
    }

    # if we have an odd number of values, bail.
    if {[expr {[llength $args]%2}] == 1} {
    # hmmm. An odd number of elements in args
    error "value for \"[lindex $args end]\" missing"
    }

    # Great. An even number of options. Let's make sure they
    # are all valid before we do anything. Note that Canonize
    # will generate an error if it finds a bogus option; otherwise
    # it returns the canonical option name
    foreach {name value} $args {
    set name [::combobox::Canonize $w option $name]
    set opts($name) $value
    }

    # process all of the configuration options
    # some (actually, most) options require us to
    # do something, like change the attributes of
    # a widget or two. Here's where we do that...
    #
    # note that the handling of disabledforeground and
    # disabledbackground is a little wonky. First, we have
    # to deal with backwards compatibility (ie: tk 8.3 and below
    # didn't have such options for the entry widget), and
    # we have to deal with the fact we might want to disable
    # the entry widget but use the normal foreground/background
    # for when the combobox is not disabled, but not editable either.

    set updateVisual 0
    foreach option [array names opts] {
    set newValue $opts($option)
    if {[info exists options($option)]} {
        set oldValue $options($option)
    }

    switch -- $option {
        -buttonbackground {
        $widgets(button) configure -background $newValue
        }
        -background {
        set updateVisual 1
        set options($option) $newValue
        }

        -borderwidth {
        $widgets(frame) configure -borderwidth $newValue
        set options($option) $newValue
        }

        -command {
        # nothing else to do...
        set options($option) $newValue
        }

        -commandstate {
        # do some value checking...
        if {$newValue != "normal" && $newValue != "disabled"} {
            set options($option) $oldValue
            set message "bad state value \"$newValue\";"
            append message " must be normal or disabled"
            error $message
        }
        set options($option) $newValue
        }

        -cursor {
        $widgets(frame) configure -cursor $newValue
        $widgets(entry) configure -cursor $newValue
        $widgets(listbox) configure -cursor $newValue
        set options($option) $newValue
        }

        -disabledforeground {
        set updateVisual 1
        set options($option) $newValue
        }

        -disabledbackground {
        set updateVisual 1
        set options($option) $newValue
        }

            -dropdownwidth {
                set options($option) $newValue
            }

        -editable {
        set updateVisual 1
         if {$newValue} {
             # it's editable...
             $widgets(entry) configure \
                 -state normal \
                 -cursor $defaultEntryCursor
         } else {
             $widgets(entry) configure \
                 -state disabled \
                 -cursor $options(-cursor)
         }
        set options($option) $newValue
        }

        -elementborderwidth {
        $widgets(button) configure -borderwidth $newValue
        $widgets(vsb) configure -borderwidth $newValue
        $widgets(dropdown) configure -borderwidth $newValue
        set options($option) $newValue
        }

        -font {
        $widgets(entry) configure -font $newValue
        $widgets(listbox) configure -font $newValue
        set options($option) $newValue
        }

        -foreground {
        set updateVisual 1
        set options($option) $newValue
        }

        -height {
        $widgets(listbox) configure -height $newValue
        HandleScrollbar $w
        set options($option) $newValue
        }

        -highlightbackground {
        $widgets(frame) configure -highlightbackground $newValue
        set options($option) $newValue
        }

        -highlightcolor {
        $widgets(frame) configure -highlightcolor $newValue
        set options($option) $newValue
        }

        -highlightthickness {
        $widgets(frame) configure -highlightthickness $newValue
        set options($option) $newValue
        }

        -image {
        if {[string length $newValue] > 0} {
            puts "old button width: [$widgets(button) cget -width]"
            $widgets(button) configure \
            -image $newValue \
            -width [expr {[image width $newValue] + 2}]
            puts "new button width: [$widgets(button) cget -width]"

        } else {
            $widgets(button) configure -image ::combobox::bimage
        }
        set options($option) $newValue
        }

        -listvar {
        if {[catch {$widgets(listbox) cget -listvar}]} {
            return -code error \
            "-listvar not supported with this version of tk"
        }
        $widgets(listbox) configure -listvar $newValue
        set options($option) $newValue
        }

        -maxheight {
        # ComputeGeometry may dork with the actual height
        # of the listbox, so let's undork it
        $widgets(listbox) configure -height $options(-height)
        HandleScrollbar $w
        set options($option) $newValue
        }

        -opencommand {
        # nothing else to do...
        set options($option) $newValue
        }

        -relief {
        $widgets(frame) configure -relief $newValue
        set options($option) $newValue
        }

        -selectbackground {
        $widgets(entry) configure -selectbackground $newValue
        $widgets(listbox) configure -selectbackground $newValue
        set options($option) $newValue
        }

        -selectborderwidth {
        $widgets(entry) configure -selectborderwidth $newValue
        $widgets(listbox) configure -selectborderwidth $newValue
        set options($option) $newValue
        }

        -selectforeground {
        $widgets(entry) configure -selectforeground $newValue
        $widgets(listbox) configure -selectforeground $newValue
        set options($option) $newValue
        }

        -state {
        if {$newValue == "normal"} {
            set updateVisual 1
            # it's enabled

            set editable [::combobox::GetBoolean \
                $options(-editable)]
            if {$editable} {
            $widgets(entry) configure -state normal
            $widgets(entry) configure -takefocus 1
            }

                    # note that $widgets(button) is actually a label,
                    # not a button. And being able to disable labels
                    # wasn't possible until tk 8.3. (makes me wonder
            # why I chose to use a label, but that answer is
            # lost to antiquity)
                    if {[info patchlevel] >= 8.3} {
                        $widgets(button) configure -state normal
                    }

        } elseif {$newValue == "disabled"}  {
            set updateVisual 1
            # it's disabled
            $widgets(entry) configure -state disabled
            $widgets(entry) configure -takefocus 0
                    # note that $widgets(button) is actually a label,
                    # not a button. And being able to disable labels
                    # wasn't possible until tk 8.3. (makes me wonder
            # why I chose to use a label, but that answer is
            # lost to antiquity)
                    if {$::tcl_version >= 8.3} {
                        $widgets(button) configure -state disabled
                    }

        } else {
            set options($option) $oldValue
            set message "bad state value \"$newValue\";"
            append message " must be normal or disabled"
            error $message
        }

        set options($option) $newValue
        }

        -takefocus {
        $widgets(entry) configure -takefocus $newValue
        set options($option) $newValue
        }

        -textvariable {
        $widgets(entry) configure -textvariable $newValue
        set options($option) $newValue
        }

        -value {
        ::combobox::SetValue $widgets(this) $newValue
        set options($option) $newValue
        }

        -width {
        $widgets(entry) configure -width $newValue
        $widgets(listbox) configure -width $newValue
        set options($option) $newValue
        }

        -xscrollcommand {
        $widgets(entry) configure -xscrollcommand $newValue
        set options($option) $newValue
        }
    }

    if {$updateVisual} {UpdateVisualAttributes $w}
    }
}

# ::combobox::UpdateVisualAttributes --
#
# sets the visual attributes (foreground, background mostly)
# based on the current state of the widget (normal/disabled,
# editable/non-editable)
#
# why a proc for such a simple thing? Well, in addition to the
# various states of the widget, we also have to consider the
# version of tk being used -- versions from 8.4 and beyond have
# the notion of disabled foreground/background options for various
# widgets. All of the permutations can get nasty, so we encapsulate
# it all in one spot.
#
# note also that we don't handle all visual attributes here; just
# the ones that depend on the state of the widget. The rest are
# handled on a case by case basis
#
# Arguments:
#    w        widget pathname
#
# Returns:
#    empty string

proc ::combobox::UpdateVisualAttributes {w} {

    upvar ::combobox::${w}::widgets     widgets
    upvar ::combobox::${w}::options     options

    if {$options(-state) == "normal"} {

    set foreground $options(-foreground)
    set background $options(-background)

    } elseif {$options(-state) == "disabled"} {

    set foreground $options(-disabledforeground)
    set background $options(-disabledbackground)
    }

    $widgets(entry)   configure -foreground $foreground -background $background
    $widgets(listbox) configure -foreground $foreground -background $background
    $widgets(button)  configure -foreground $foreground
    $widgets(vsb)     configure -background $background -troughcolor $background
    $widgets(frame)   configure -background $background

    # we need to set the disabled colors in case our widget is disabled.
    # We could actually check for disabled-ness, but we also need to
    # check whether we're enabled but not editable, in which case the
    # entry widget is disabled but we still want the enabled colors. It's
    # easier just to set everything and be done with it.

    if {$::tcl_version >= 8.4} {
    $widgets(entry) configure \
        -disabledforeground $foreground \
        -disabledbackground $background
    $widgets(button)  configure -disabledforeground $foreground
    $widgets(listbox) configure -disabledforeground $foreground
    }
}

# ::combobox::SetValue --
#
#    sets the value of the combobox and calls the -command,
#    if defined
#
# Arguments:
#
#    w          widget pathname
#    newValue   the new value of the combobox
#
# Returns
#
#    Empty string

proc ::combobox::SetValue {w newValue} {

    upvar ::combobox::${w}::widgets     widgets
    upvar ::combobox::${w}::options     options
    upvar ::combobox::${w}::ignoreTrace ignoreTrace
    upvar ::combobox::${w}::oldValue    oldValue

    if {[info exists options(-textvariable)] \
        && [string length $options(-textvariable)] > 0} {
    set variable ::$options(-textvariable)
    set $variable $newValue
    } else {
    set oldstate [$widgets(entry) cget -state]
    $widgets(entry) configure -state normal
    $widgets(entry) delete 0 end
    $widgets(entry) insert 0 $newValue
    $widgets(entry) configure -state $oldstate
    }

    # set our internal textvariable; this will cause any public
    # textvariable (ie: defined by the user) to be updated as
    # well
#    set ::combobox::${w}::entryTextVariable $newValue

    # redefine our concept of the "old value". Do it before running
    # any associated command so we can be sure it happens even
    # if the command somehow fails.
    set oldValue $newValue


    # call the associated command. The proc will handle whether or
    # not to actually call it, and with what args
    CallCommand $w $newValue

    return ""
}

# ::combobox::CallCommand --
#
#   calls the associated command, if any, appending the new
#   value to the command to be called.
#
# Arguments:
#
#    w         widget pathname
#    newValue  the new value of the combobox
#
# Returns
#
#    empty string

proc ::combobox::CallCommand {w newValue} {
    upvar ::combobox::${w}::widgets widgets
    upvar ::combobox::${w}::options options

    # call the associated command, if defined and -commandstate is
    # set to "normal"
    if {$options(-commandstate) == "normal" && \
        [string length $options(-command)] > 0} {
    set args [list $widgets(this) $newValue]
    uplevel \#0 $options(-command) $args
    }
}


# ::combobox::GetBoolean --
#
#     returns the value of a (presumably) boolean string (ie: it should
#     do the right thing if the string is "yes", "no", "true", 1, etc
#
# Arguments:
#
#     value       value to be converted
#     errorValue  a default value to be returned in case of an error
#
# Returns:
#
#     a 1 or zero, or the value of errorValue if the string isn't
#     a proper boolean value

proc ::combobox::GetBoolean {value {errorValue 1}} {
    if {[catch {expr {([string trim $value])?1:0}} res]} {
    return $errorValue
    } else {
    return $res
    }
}

# ::combobox::convert --
#
#     public routine to convert %x, %y and %W binding substitutions.
#     Given an x, y and or %W value relative to a given widget, this
#     routine will convert the values to be relative to the combobox
#     widget. For example, it could be used in a binding like this:
#
#     bind .combobox <blah> {doSomething [::combobox::convert %W -x %x]}
#
#     Note that this procedure is *not* exported, but is intended for
#     public use. It is not exported because the name could easily
#     clash with existing commands.
#
# Arguments:
#
#     w     a widget path; typically the actual result of a %W
#           substitution in a binding. It should be either a
#           combobox widget or one of its subwidgets
#
#     args  should one or more of the following arguments or
#           pairs of arguments:
#
#           -x <x>      will convert the value <x>; typically <x> will
#                       be the result of a %x substitution
#           -y <y>      will convert the value <y>; typically <y> will
#                       be the result of a %y substitution
#           -W (or -w)  will return the name of the combobox widget
#                       which is the parent of $w
#
# Returns:
#
#     a list of the requested values. For example, a single -w will
#     result in a list of one items, the name of the combobox widget.
#     Supplying "-x 10 -y 20 -W" (in any order) will return a list of
#     three values: the converted x and y values, and the name of
#     the combobox widget.

proc ::combobox::convert {w args} {
    set result {}
    if {![winfo exists $w]} {
    error "window \"$w\" doesn't exist"
    }

    while {[llength $args] > 0} {
    set option [lindex $args 0]
    set args [lrange $args 1 end]

    switch -exact -- $option {
        -x {
        set value [lindex $args 0]
        set args [lrange $args 1 end]
        set win $w
        while {[winfo class $win] != "Combobox"} {
            incr value [winfo x $win]
            set win [winfo parent $win]
            if {$win == "."} break
        }
        lappend result $value
        }

        -y {
        set value [lindex $args 0]
        set args [lrange $args 1 end]
        set win $w
        while {[winfo class $win] != "Combobox"} {
            incr value [winfo y $win]
            set win [winfo parent $win]
            if {$win == "."} break
        }
        lappend result $value
        }

        -w -
        -W {
        set win $w
        while {[winfo class $win] != "Combobox"} {
            set win [winfo parent $win]
            if {$win == "."} break;
        }
        lappend result $win
        }
    }
    }
    return $result
}

# ::combobox::Canonize --
#
#    takes a (possibly abbreviated) option or command name and either
#    returns the canonical name or an error
#
# Arguments:
#
#    w        widget pathname
#    object   type of object to canonize; must be one of "command",
#             "option", "scan command" or "list command"
#    opt      the option (or command) to be canonized
#
# Returns:
#
#    Returns either the canonical form of an option or command,
#    or raises an error if the option or command is unknown or
#    ambiguous.

proc ::combobox::Canonize {w object opt} {
    variable widgetOptions
    variable columnOptions
    variable widgetCommands
    variable listCommands
    variable scanCommands

    switch $object {
    command {
        if {[lsearch -exact $widgetCommands $opt] >= 0} {
        return $opt
        }

        # command names aren't stored in an array, and there
        # isn't a way to get all the matches in a list, so
        # we'll stuff the commands in a temporary array so
        # we can use [array names]
        set list $widgetCommands
        foreach element $list {
        set tmp($element) ""
        }
        set matches [array names tmp ${opt}*]
    }

    {list command} {
        if {[lsearch -exact $listCommands $opt] >= 0} {
        return $opt
        }

        # command names aren't stored in an array, and there
        # isn't a way to get all the matches in a list, so
        # we'll stuff the commands in a temporary array so
        # we can use [array names]
        set list $listCommands
        foreach element $list {
        set tmp($element) ""
        }
        set matches [array names tmp ${opt}*]
    }

    {scan command} {
        if {[lsearch -exact $scanCommands $opt] >= 0} {
        return $opt
        }

        # command names aren't stored in an array, and there
        # isn't a way to get all the matches in a list, so
        # we'll stuff the commands in a temporary array so
        # we can use [array names]
        set list $scanCommands
        foreach element $list {
        set tmp($element) ""
        }
        set matches [array names tmp ${opt}*]
    }

    option {
        if {[info exists widgetOptions($opt)] \
            && [llength $widgetOptions($opt)] == 2} {
        return $opt
        }
        set list [array names widgetOptions]
        set matches [array names widgetOptions ${opt}*]
    }

    }

    if {[llength $matches] == 0} {
    set choices [HumanizeList $list]
    error "unknown $object \"$opt\"; must be one of $choices"

    } elseif {[llength $matches] == 1} {
    set opt [lindex $matches 0]

    # deal with option aliases
    switch $object {
        option {
        set opt [lindex $matches 0]
        if {[llength $widgetOptions($opt)] == 1} {
            set opt $widgetOptions($opt)
        }
        }
    }

    return $opt

    } else {
    set choices [HumanizeList $list]
    error "ambiguous $object \"$opt\"; must be one of $choices"
    }
}

# ::combobox::HumanizeList --
#
#    Returns a human-readable form of a list by separating items
#    by columns, but separating the last two elements with "or"
#    (eg: foo, bar or baz)
#
# Arguments:
#
#    list    a valid tcl list
#
# Results:
#
#    A string which as all of the elements joined with ", " or
#    the word " or "

proc ::combobox::HumanizeList {list} {

    if {[llength $list] == 1} {
    return [lindex $list 0]
    } else {
    set list [lsort $list]
    set secondToLast [expr {[llength $list] -2}]
    set most [lrange $list 0 $secondToLast]
    set last [lindex $list end]

    return "[join $most {, }] or $last"
    }
}

# This is some backwards-compatibility code to handle TIP 44
# (http://purl.org/tcl/tip/44.html). For all private tk commands
# used by this widget, we'll make duplicates of the procs in the
# combobox namespace.
#
# I'm not entirely convinced this is the right thing to do. I probably
# shouldn't even be using the private commands. Then again, maybe the
# private commands really should be public. Oh well; it works so it
# must be OK...
foreach command {TabToWindow CancelRepeat ListboxUpDown} {
    if {[llength [info commands ::combobox::tk$command]] == 1} break;

    set tmp [info commands tk$command]
    set proc ::combobox::tk$command
    if {[llength [info commands tk$command]] == 1} {
        set command [namespace which [lindex $tmp 0]]
        proc $proc {args} "uplevel $command \$args"
    } else {
        if {[llength [info commands ::tk::$command]] == 1} {
            proc $proc {args} "uplevel ::tk::$command \$args"
        }
    }
}

# end of combobox.tcl