This is a bit of code I wrote recently to parse an XML report write up into a Tk canvas display, and then produce postscript from it. It uses Iwidgets scrolledcanvas, but you can achieve the same with a normal canvas and a couple of scrollbars - I'm just lazy.
Before I give the code, here is an example XML document in this report markup (it contains all the elements allowed). You could extend the system to easily add support for new elements, and generalize to allow any XML language. I'm considering implementing a Formatting Objects Processor in Tcl, and when I do I'll write a proper TkCanvas driver for it so you can convert XML documents into TkCanvas displays using just XSLT/FOP.

OK - here's a sample doc:
 <?xml version="1.0"?>
 <document>
     <title>XML to Tk Canvas</title>
     <heading1>1. First Section</heading1>
     <heading2>1.1 Sub section</heading2>
     <text>This is some text. Here is a
         <quote>qoute</quote>
     </text>
     <heading2>1.2 Lists</heading2>
     <text>
      This is a list:
      <list>
          <item>Item one</item>
          <item>The second item</item>
      </list>
      </text>
 </document>

And here is the code:

 package require Tk
 package require Iwidgets
 package require xml

 # Menus
 menu .mb
 . configure -menu .mb
 menu .mb.file -tearoff 0
 .mb add cascade -label File -menu .mb.file
 .mb.file add command -label "Open" -command {openFile}
 .mb.file add command -label "2EPS" -command {createPS}

 iwidgets::scrolledcanvas .c -width 21c -height 15c
 [.c childsite] configure -bg white -state normal -cursor xterm
 pack .c -fill both -expand 1

 update idletasks

 set parser [xml::parser -elementstartcommand StartTag \
                       -elementendcommand EndTag \
                       -characterdatacommand CData]
 
 list Stack
 proc push {} {
    global Stack options
    lappend Stack [list [array get options]]
 }

 proc pop {} {
    global Stack options
    array set options [join [lindex $Stack end]]
    set Stack [lreplace $Stack end end]
 }

 set nextline 1.5c
 array set options {
    width       18c
    offset      1.3
    font        {{Times New Roman} 12}
    indent      1.0
    anchor      nw
    justify     left
 }

 proc Title {} {
    global options
    push
    array set options {
        indent  9
        anchor  center
        font    {Arial 30 bold}
        justify center
    }
 }

 proc Heading1 {} {
    global options
    push
    array set options {
        indent  0
        anchor nw
        font    {Arial 12 bold}
        justify     left
    }
 }

 proc Heading2 {} {
    global options
    push
    array set options {
        indent 0.4
        anchor nw
        font    {Arial 10 bold}
        justify     left
    }
 }

 proc Default {} {
    global options
    push
    array set options {
        indent  1
        anchor  nw
        font    {{Times New Roman} 12}
        justify     left
    }
 }

 proc Quote {} {
    global options
    push
    array set options {
        indent 1.3
        anchor nw
        font {{Times New Roman} 12 italic}
        justify     left
    }
 }

 proc List {} {
    global options
    push
    array set options {
        indent 1.4
    }
 }

 proc Item {} {
    push
    global nextline
    set position [expr {$nextline + 6}]
    .c create oval 2.4c $position 2.3c [expr {$position + 5}] -fill black
 }

 proc br {} {
    global nextline
    incr nextline 14
 }


 proc StartTag {tag attrs args} {
    switch -exact -- $tag {
        document    { # Do nothing }
        title       {Title}
        heading1    {Heading1}
        heading2    {Heading2}
        text        {Default}
        quote       {Quote}
        list        {List}
        item        {Item}
        br          {br}
        default     {puts "Unknown tag: $tag"}
    }
 }

 proc CData {text} {
    if {[string length $text]<3} {return}
    global options nextline
    set ntext ""
    foreach line [split $text \n] {
        append ntext [string trim $line]\n
    }
    set t [.c create text [expr {$options(indent) + $options(offset)}]c\
        $nextline -width $options(width)\
        -font $options(font) -anchor $options(anchor)\
        -text [string trim $ntext]]
    update idletasks
    set nextline [lindex [.c bbox $t] 3]
 }

 proc EndTag {args} {
    if {[lindex $args 0] != "br"} {
        pop
    }
 }

 proc openFile {} {
    global parser env
    set filename [tk_getOpenFile -defaultextension xml \
                                -filetypes {{{XML Files} .xml}} \
                                -initialdir $env(HOME) \
                                -initialfile input.xml]
    if {$filename == ""} {return}

    set fid [open $filename]
    set xml [read $fid]
    close $fid

    $parser parse $xml

    .c yview moveto 0
 }

 proc createPS {} {
    global nextline env
    set ps [.c postscript -colormode gray \
            -x 0 -y 0 -width 21c -height $nextline \
            -pageheight 29.7c -pagewidth 21c]

    set filename [tk_getSaveFile -defaultextension eps \
                    -filetypes {{{Encapsulated PostScript files} .ps}} \
                    -initialdir $env(HOME) \
                    -initialfile output.eps]
    if {$filename == ""} {return}

    set fid [open $filename w]
    puts $fid $ps
    close $fid
    update idletasks
 }


Have fun! '''NEM'''