unlimited undo's for text fields

[Wouter]

Hi All,

For those who like unlimited undo's (or is it ram limited undo's?) an 
undo framework starter for text in fields.
This script can be placed in a stackscript and will act on all 
(editable) fields.
Drag dropping text from one field to the other is supported.
It is functional and tested on OS X. But for the other platforms I 
don't know yet.
Adapt as necessary and beware of the mail wraps!

global gHistory
local lSC,lData

on rawkeydown x
   writeHistory x
   pass rawkeydown
end rawkeydown

on dragstart
   put the selectedchunk into lSC
   pass dragstart
end dragstart

on dragend
   put the dragData["text"] into lData
   send "checkdragdata" to me in 20 millisecs
   pass dragend
end dragend

on checkdragdata
   put the selectedchunk into tSC
   get word -2 to -1 of lSC
   put word 1 to 7 of the long id of it into tFNameOrig
   get word -2 to -1 of tSC
   put word 1 to 7 of the long id of it into tFNameDest
   if tFNameOrig = tFNameDest and not (word 2 of tSC > word 4 of tSC) 
then
       put "d",lSC,tSC,hexadize(lData) & cr after gHistory[tFNameDest]
   else if tFNameOrig <> tFNameDest then
     delete word 3 to 4 of lSC
     put "x",lSC,hexadize(lData) & cr after gHistory[tFNameOrig]
     put "v",tSC,hexadize(lData) & cr after gHistory[tFNameDest]
   end if
   put "" into lSC
   put "" into lData
end checkdragdata

### first item indicates the action
### w = write
### v = paste
### x = cut
### b = backspace
### d = dragplaced

on writeHistory x
   put the selectedchunk into tSC
   get word -2 to -1 of tSC
   put word 1 to 7 of the long id of it into tFName
   if the commandkey is down then
     switch x
     case "122"  ### z
       reverseHistory
       break
     case "118"  ### v
       put clipboardData["text"] into x
       put "v",tSC,hexadize(x) & cr after gHistory[tFName]
       break
     case "120"  ###   x
       put the value of tSC into x
       if x <> "" then
         delete word 3 to 4 of tSC
         put "x",tSC,hexadize(x) & cr after gHistory[tFName]
       end if
       break
     end switch
   else
     switch x
     case "65421" ### enter in field
     case "65307" ### escape key
     case "65308" ### scrollwheel up and down
     case "65309"
     case "65361" ### arrowkeys
     case "65363"
     case "65362"
     case "65364"
       -- do nothing
       break
     case "65288"  ### backspace
       if word 4 of tSC <> 0 then
         if word 2 of tSC < word 4 of tSC then
           get the value of tSC
           delete word 3 to 4 of tsC
         else if word 2 of tSC > word 4 of tSC then
           delete word 2 to 3 of tSC
           get the value of tsC
         end if
         put hexadize(it) into x
         put "b",tSC,x & cr after gHistory[tFName]  ## b = backspace
       end if
       break
     case "65293"  ### return in field
       delete word 3 to 4 of tSC
       put "w",tSC,hexadize(return) & cr after gHistory[tFName]
       break
     default
       delete word 3 to 4 of tSC
       put "w",tSC,hexadize(numtochar(x)) & cr after gHistory[tFName]
       break
     end switch
   end if
end writeHistory

on reverseHistory
   put word 1 to 7 of the the focusedobject into tFName
   if gHistory[tFName] = "" then
     beep
     exit reverseHistory
   end if
   get line -1 of gHistory[tFName]
   delete line - 1 of gHistory[tFName]
   switch item 1 of it
   case "b"
     put dehexadize(last item of it) into x
     if x = return then put "cr" into x
     else if x = space then put "space" into x
     else if x = tab then put "tab" into x
     else
       replace quote with quote & "&quote&" & quote in x
       replace cr with quote&"&cr&"& quote in x
       put quote & x & quote into x
     end if
     do "put" &&  x  && "before" && item 2 of it
     break
   case "w"
     do "delete" && item 2 of it
     break
   case "v"
     put dehexadize(last item of it) into x
     put the num of chars in x into y
     put word 2 of item 2 of it + y - 1 into word 4 of item 2 of it
     do " delete" &&  item 2 of it
     break
   case "x"
     put dehexadize(last item of it) into x
     if x = return then put "cr" into x
     else if x = space then put "space" into x
     else if x = tab then put "tab" into x
     else
       replace quote with quote & "&quote&" & quote in x
       replace cr with quote&"&cr&"& quote in x
       put quote & x & quote into x
     end if
     do " put" && x && "before" &&  item 2 of it
     break
   case "d"
     put dehexadize(last item of it) into x
     if last char of x = cr then add 1 to word 4 of item 3 of it
     if the num of lines in x > 1 then delete last char of x
     if x = return then put "cr" into x
     else if x = space then put "space" into x
     else if x = tab then put "tab" into x
     else
       replace quote with quote & "&quote&" & quote in x
       replace cr with quote&"&cr&"& quote in x
       put quote & x & quote into x
     end if
     do "delete" && item 3 of it
     delete word 3 to 4 of item 2 of it
     do " put" && x && "before" &&  item 2 of it
     break
   end switch
end reverseHistory

### Big Endian BinaryDecode ###
function hexadize sx
   get binarydecode("H*", sx, x1)
   return x1
end hexadize

### Big Endian Binary Encode ###
function deHexadize sx
   replace space with "" in sx
   try
     get binaryEncode("H*", sx, x1)
   catch errornum
     put "no hex value" into it
   finally
     return it
   end try
end deHexadize

###################
## for test purposes ##
###################

on emptyHistory
   delete global  gHistory
end emptyHistory

on putHistory
   put word 1 to 7 of the the focusedobject into tFName
   if the optionkey is down then put the keys of gHistory
   else put gHistory[tFName]
end putHistory


Greetings,
WA