#! /usr/local/bin/wish8.5

#==============================================================================
# Demo:	wcb::callback <text> before insert <callback> ...
#	wcb::callback <text> before delete <callback>
#	wcb::callback <text> before selset <callback>
#	wcb::callback <text> before motion <callback>
#	wcb::callback <text>  after insert <callback>
#	wcb::callback <text>  after delete <callback>
#	wcb::cancel
#	wcb::extend <arg>
#
# Copyright (c) 2004-2020  Csaba Nemethi (E-mail: csaba.nemethi@t-online.de)
#==============================================================================

package require Tk 8.4	;# because of the undo mechanism for text widgets
package require wcb

wm title . "Texttest #2"

#
# Add some entries to the Tk option database
#
source [file join [file dirname [info script]] option.tcl]

#
# Text .txt with activated undo mechanism
#
set width 50
text .txt -width $width -height 12 -setgrid true -wrap none -background white \
	  -font TkFixedFont
.txt configure -undo yes
.txt tag configure prog -foreground red
.txt tag configure user -foreground DarkGreen
.txt insert end "Everything you type or paste into this window will\n"	 prog
.txt insert end "be displayed in dark green.  You cannot make any\n"	 prog
.txt insert end "changes or selections in this red area, and will\n"	 prog
.txt insert end "not be able to insert more than $width characters in\n" prog
.txt insert end "any line.\n"						 prog
.txt insert end "--------------------------------------------------\n"	 prog
set limit [.txt index insert]

#
# Label .pos displaying the current cursor position
#
label .pos -textvariable pos

#
# Button .close
#
button .close -text Close -command exit

#
# Define 5 before- and 2 after-callbacks for .txt
#
wcb::callback .txt before insert protectRedArea changeColor
wcb::callback .txt before delete protectRedArea
wcb::callback .txt before selset protectRedArea
wcb::callback .txt before motion displayPos
wcb::callback .txt  after insert "checkLines $width"
wcb::callback .txt  after delete "checkLines $width"

#
# Callback procedure protectRedArea
#
# The parameters following w can be interpreted either as
# "index string ?tagList string tagList ...?" (for an insert
# callback), or as "from ?to?" (for a delete callback),
# or as "from ?to from to ...?" (for a selset callback).
#
proc protectRedArea {w idx args} {
    global limit
    if {[$w compare $idx < $limit]} {
	wcb::cancel
    }
}

#
# Callback procedure changeColor
#
proc changeColor {w args} {
    wcb::extend user
}

#
# Callback procedure displayPos
#
proc displayPos {w idx} {
    set index [$w index $idx]
    scan $index "%d.%d" line column
    incr column

    global pos
    set pos [format "Line: %d   Column: %d" $line $column]
}

#
# Callback procedure checkLines
#
# The parameter args can be interpreted both as "index
# string ?tagList string tagList ...?" (for an insert
# callback) and as "from ?to?" (for a delete callback).
#
proc checkLines {maxCharsPerLine w args} {
    #
    # Undo the last insert or delete action if necessary
    #
    scan [$w index end] "%d" lastLine
    for {set line 1} {$line < $lastLine} {incr line} {
	scan [$w index $line.end] "%d.%d" dummy charsInLine
	if {$charsInLine > $maxCharsPerLine} {
	    $w edit undo
	    bell
	    break
	}
    }

    #
    # Clear the undo and redo stacks, and display the new cursor position
    #
    $w edit reset
    displayPos $w insert
}

#
# Manage the widgets
#
pack .close -side bottom -pady 7p
pack .pos -side bottom
pack .txt -expand yes -fill both

displayPos .txt insert
focus .txt
