managing multi-listboxes

There have been several folks struggling with how to manage a dual listbox style application where items from a master list are moved to a destination list. I wrote some code to do that many years ago. This is an updated version with comments. I am hoping folks can follow along. When running the program looks like this:

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Here is the code:

'Friuty List - an example of how to manage a listbox as a destination list building
'  the list from a master listbox.  This would work with comboboxes also.
'by Brad Moore - placed into the Public Domain Jan 2006
 
nomainwin
 
'this is how many entries the destination list box can hold
maxEntries = 100
 
'create the arrays
DIM arrayOne$(12)
DIM arrayTwo$(maxEntries)
 
'this is the master data - you can do this with read/data statements also,
'  wondering how this works? - check out the WORD$ function in the helpfile.
a$ = "Apples Bananas Cherries Figs Grapefriut Honeydew Kiwi Lime Mango Nectarine Papaya Pear"
FOR x = 1 TO 12 : arrayOne$(x) = word$(a$,x) : NEXT x
 
'initialize our counter for items in the destination listbox
idx = 0
 
'setup the window and controls
WindowWidth = 280
WindowHeight = 260
UpperLeftX = INT((DisplayWidth/2)-(WindowWidth/2))
UpperLeftY = INT((DisplayHeight/2)-(WindowHeight/2))
 
listbox #main.lbx1,arrayOne$(),WAIT,10,10,100,170
listbox #main.lbx2,arrayTwo$(),WAIT,158,10,100,170
button #main.moveBtn,">",[move],UL,114,30,40,30
button #main.deleteBtn,"Delete",[delete],UL,114,62,40,30
button #main.deleteBtn,"Sort",[sort],UL,114,94,40,30
button #main.closeBtn, "Close",[quit],UL,158,189,100,30
button #main.inspectBtn, "Inspect Array",[inspect],UL,52,189,100,30
 
'open the window
OPEN "Friuty List" FOR dialog AS #main
PRINT #main,"trapclose [quit]"
PRINT #main.lbx1,"selectindex 1"
WAIT
 
[move]
'get the index value for the item in the master list
PRINT #main.lbx1,"selectionindex? i"
'make sure there is room to add another item
IF idx = maxEntries THEN
    notice "The destination list already contains the maximum number of entries"
    WAIT
END IF
'increment the index and add the item
idx = idx + 1
arrayTwo$(idx) = arrayOne$(i)
'reload causes the listbox view to be refreshed so our item shows up
PRINT #main.lbx2,"reload"
WAIT
 
[delete]
'get the index value for the item in the destination list
PRINT #main.lbx2,"selectionindex? i"
'if this is not the last item we need to shift the array up to fill the gap
IF i < idx THEN
   FOR x = i TO idx - 1
      arrayTwo$(x) = arrayTwo$(x+1)
   NEXT x
END IF
'set the last item to a null string
arrayTwo$(idx) = ""
'decrement the total number of items in the destination array
idx = idx - 1
'reload causes the listbox view to be refreshed so our item shows up
PRINT #main.lbx2,"reload"
WAIT
 
 
[inspect]
'inspect opens a new window in dialog modal form - set up that window
WindowWidth = 372
WindowHeight = 470
UpperLeftX = INT((DisplayWidth-(2 * WindowWidth))/2)
UpperLeftY = INT((DisplayHeight-(2 * WindowHeight))/2)
button  #inspect.closeBtn, "Close", [closeMe], UL, 225, 395, 125, 30
texteditor  #inspect.tedit, 9, 13, 340, 375
'open the window
OPEN "Array Inspector" FOR Dialog_modal AS #inspect
#inspect "trapclose [closeMe]"
#inspect "font ms_sans_serif 10"
 
'initialize the output string
IF idx = 0 THEN
    OUT$ = "There are no items in the destination array."
ELSE
    OUT$ = "There are " + STR$(idx) + " items in the destination array." + CHR$(10)
END IF
 
'add the array items to the output string.  Note the right$ trick which pads index with leading zeros
FOR x = 1 TO idx
    OUT$ = OUT$ + "Item " + RIGHT$("000" + STR$(x),3) + " = " + arrayTwo$(x) + CHR$(10)
NEXT x
'dump the output string to the texteditor
#inspect.tedit OUT$
WAIT
 
[closeMe]
CLOSE #inspect
WAIT
 
 
[sort]
'if there is more than one item in the destination array call the sort function to sort it
IF idx > 1 THEN sort arrayTwo$(), 1, idx
'reload causes the listbox view to be refreshed so our item shows up
PRINT #main.lbx2,"reload"
WAIT
 
[quit]
CLOSE #main
END