# supertext.tcl v1.01
#
# Copyright (c) 1998 Bryan Oakley
# All Rights Reserved
#
# this code is freely distributable, but is provided as-is with
# no waranty expressed or implied.

# send comments to oakley@channelpoint.com

# What is this?
# 
# This is a replacement for (or superset of , or subclass of, ...) 
# the tk text widget. Its big feature is that it supports unlimited
# undo. It also has two poorly documented options: -preproc and 
# -postproc. 

# The entry point to this widget is supertext::text; it takes all of
# the same arguments as the standard text widget and exhibits all of
# the same behaviors.  The proc supertext::overrideTextCommand may be
# called to have the supertext widget be used whenever the command
# "text" is used (ie: it imports supertext::text as the command "text"). 
# Use at your own risk...

# To access the undo feature, use ".widget undo". It will undo the
# most recent insertion or deletion. On windows and the mac
# this command is bound to <Control-z>; on unix it is bound to
# <Control-_>

# if you are lucky, you might find documentation here:
# http://www1.clearlight.com/~oakley/tcl/supertext.html

package provide supertext 1.01

namespace eval supertext {
    variable undo
    variable undoIndex
    variable text "::text"
    variable preProc
    variable postProc
    namespace export text
}

# this proc is probably attempting to be more clever than it should...
# When called, it will (*gasp*) rename the tk command "text" to "_text_", 
# then import our text command into the global scope. 
#
# Use at your own risk!

proc supertext::overrideTextCommand {} {
    variable text
    set text "::_text_"
    rename ::text $text
    uplevel #0 namespace import supertext::text
}

proc supertext::text {w args} {
    variable text
    variable undo
    variable undoIndex
    variable preProc
    variable postProc

    # this is what we will rename our widget proc to...
    set original __$w

    # do we have any of our custom options? If so, process them and 
    # strip them out before sending them to the real text command
    if {[set i [lsearch -exact $args "-preproc"]] >= 0} {
        set j [expr $i + 1]
        set preProc($original) [lindex $args $j]
        set args [lreplace $args $i $j]
    } else {
        set preProc($original) {}
    }

    if {[set i [lsearch -exact $args "-postproc"]] >= 0} {
        set j [expr $i + 1]
        set postProc($original) [lindex $args $j]
        set args [lreplace $args $i $j]
    } else {
        set postProc($original) {}
    }

    # let the text command create the widget...
    eval $text $w $args

    # now, rename the resultant widget proc so we can create our own
    rename ::$w $original

    # here's where we create our own widget proc.
    proc ::$w {command args} \
        "namespace eval supertext widgetproc $w $original \$command \$args"
    
    # set up platform-specific binding for undo; the only one I'm
    # really sure about is winders; the rest will stay the same for
    # now until someone has a better suggestion...
    switch $::tcl_platform(platform) {
        unix                 {
                event add <<Undo>> <Control-z>
                event add <<Undo>> <Control-Z>
        }
        windows         {
                event add <<Undo>> <Control-z>
                event add <<Undo>> <Control-Z>
        }
        macintosh         {
                event add <<Undo>> <Control-z>
                event add <<Undo>> <Control-Z>
        }
    }
    bind $w <<Undo>> "$w undo"

    set undo($original)        {}
    set undoIndex($original) -1
    set clones($original) {}

    return $w
}

# this is the command that we associate with a supertext widget. 
proc supertext::widgetproc {this w command args} {

    variable undo
    variable undoIndex
    variable preProc
    variable postProc

    # these will be the arguments to the pre and post procs
    set originalCommand $command
    set originalArgs $args

    # is there a pre-proc? If so, run it. If there is a problem,
    # die. This is potentially bad, because once there is a problem
    # in a preproc the user must fix the preproc -- there is no
    # way to unconfigure the preproc. Oh well. The other choice
    # is to ignore errors, but then how will the caller know if
    # the proc fails?
    if {[info exists preProc($w)] && $preProc($w) != ""} {
        if {[catch "$preProc($w) command args" error]} {
            return -code error "error during processing of -preproc: $error"
        }
    }


    # if the command is "undo", we need to morph it into the appropriate
    # command for undoing the last item on the stack
    if {$command == "undo"} {

        if {$undoIndex($w) == ""} {
            # ie: last command was anything _but_ an undo...
            set undoIndex($w) [expr [llength $undo($w)] -1]
        }

        # if the index is pointing to a valid list element, 
        # lets undo it...
        if {$undoIndex($w) < 0} {
            # nothing to undo...
            bell

        } else {
            
            # data is a list comprised of a command token
            # (i=insert, d=delete) and parameters related 
            # to that token
            set data [lindex $undo($w) $undoIndex($w)]

            if {[lindex $data 0] == "d"} {
                set command "delete"
            } else {
                set command "insert"
            }
            set args [lrange $data 1 end]

            # adjust the index
            incr undoIndex($w) -1

        }
    }

    # now, process the command (either the original one, or the morphed
    # undo command
    switch $command {

        reset_undo {
                set undo($w) ""
                set undoIndex($w) ""
                set result {}
        }

        configure {
            # we have to deal with configure specially, since the
            # user could try to configure the -preproc or -postproc
            # options...
            
            if {[llength $args] == 0} {
                # first, the case where they just type "configure"; lets 
                # get it out of the way
                set list [$w configure]
                lappend list [list -preproc preproc Preproc {} $preProc($w)]
                lappend list [list -postproc postproc Postproc {} $postProc($w)]
                set result $list
                
                
            } elseif {[llength $args] == 1} {
                # this means they are wanting specific configuration 
                # information
                set option [lindex $args 0]
                if {$option == "-preproc"} {
                    set result [list -preproc preproc Preproc {} $preProc($w)]

                } elseif {$option == "-postproc"} {
                    set result [list -postproc postproc Postproc {} $postProc($w)]
                    
                } else {
                    if {[catch "$w $command $args" result]} {
                        regsub $w $result $this result
                        return -code error $result
                    }
                }

            } else {
                # ok, the user is actually configuring something... 
                # we'll deal with our special options first
                if {[set i [lsearch -exact $args "-preproc"]] >= 0} {
                    set j [expr $i + 1]
                    set preProc($w) [lindex $args $j]
                    set args [lreplace $args $i $j]
                    set result {}
                }

                if {[set i [lsearch -exact $args "-postproc"]] >= 0} {
                    set j [expr $i + 1]
                    set postProc($w) [lindex $args $j]
                    set args [lreplace $args $i $j]
                    set result {}
                }

                # now, process any remaining args
                if {[llength $args] > 0} {
                    if {[catch "$w $command $args" result]} {
                        regsub $w $result $this result
                        return -code error $result
                    }
                }
            }
        }

        undo {
            # if an undo command makes it to here, that means there 
            # wasn't anything to undo; this effectively becomes a
            # no-op
            set result {}
        }

        insert {

            if {[catch {set index  [text_index $w [lindex $args 0]]}]} {
                set index [lindex $args 0]
            }

            # since the insert command can have an arbitrary number
            # of strings and possibly tags, we need to ferret that out
            # now... what a pain!
            set myargs [lrange $args 1 end]
            set length 0
            while {[llength $myargs] > 0} {
                incr length [string length [lindex $myargs 0]]
                if {[llength $myargs] > 1} {
                    # we have a tag...
                    set myargs [lrange $myargs 2 end]
                } else {
                    set myargs [lrange $myargs 1 end]
                }
            }

            # now, let the real widget command do the dirty work
            # of inserting the text. If we fail, do some munging 
            # of the error message so the right widget name appears...

            if {[catch "$w $command $args" result]} {
                regsub $w $result $this result
                return -code error $result
            }

            # we need this for the undo stack; index2 couldn't be
            # computed until after we inserted the data...
            set index2 [text_index $w "$index + $length chars"]

            if {$originalCommand == "undo"} {
                # let's do a "see" so what we just did is visible;
                # also, we'll move the insertion cursor to the end
                # of what we just did...
                $w see $index2
                $w mark set insert $index2
                
            } else {
                # since the original command wasn't undo, we need
                # to reset the undoIndex. This means that the next
                # time an undo is called for we'll start at the 
                # end of the stack
                set undoIndex($w) ""
            }

            # add a delete command on the undo stack.
            lappend undo($w) "d $index $index2"

        }

        delete {

            # this converts the insertion index into an absolute address
            set index [text_index $w [lindex $args 0]]

            # lets get the data we are about to delete; we'll need
            # it to be able to undo it (obviously. Duh.)
            set data [eval $w get $args]

            # add an insert on the undo stack
            lappend undo($w) [list "i" $index $data]

            if {$originalCommand == "undo"} {
                # let's do a "see" so what we just did is visible;
                # also, we'll move the insertion cursor to a suitable
                # spot
                $w see $index
                $w mark set insert $index

            } else {
                # since the original command wasn't undo, we need
                # to reset the undoIndex. This means that the next
                # time an undo is called for we'll start at the 
                # end of the stack
                set undoIndex($w) ""
            }

            # let the real widget command do the actual deletion. If
            # we fail, do some munging of the error message so the right
            # widget name appears...
            if {[catch "$w $command $args" result]} {
                regsub $w $result $this result
                return -code error $result
            }
        }
        
        default {
            # if the command wasn't one of the special commands above,
            # just pass it on to the real widget command as-is. If
            # we fail, do some munging of the error message so the right
            # widget name appears...
            if {[catch "$w $command $args" result]} {
                regsub $w $result $this result
                return -code error $result
            }
        }
    }

    # is there a post-proc? If so, run it. 
    if {[info exists postProc($w)] && $postProc($w) != ""} {
        if {[catch "$postProc($w) originalCommand originalArgs" error]} {
            return -code error "error during processing of -postproc: $error"
        }
    }


    # we're outta here! (I think this is faster than a 
    # return, though I'm not 100% sure on this...)
    set result $result
}

# this returns a normalized index (ie: line.column), with special
# handling for the index "end"; to undo something we pretty much
# _have_ to have a precise row and column number.
proc supertext::text_index {w i} {
    if {$i == "end"} {
        set index [$w index "end-1c"]
    } else {
        set index [$w index $i]
    }

    return $index
}