scrolled canvas in pane

proc scrolled_canvas w {
    set wp [file root $w] ;# w does not exist yet - hen/egg problem
    scrollbar $wp.y -command "$w yview"
    grid [canvas $w -xscrollc "$wp.x set" -yscrollc "$wp.y set"] \
	    $wp.y -sticky ns
    grid [scrollbar $wp.x -ori hori -command "$w xview"] -sticky ew
    grid $w -sticky news
    if {$wp eq ""} {set wp .}
    grid columnconfig $wp 0 -weight 1
    #grid columnconfig $wp 1 -weight 0
    grid rowconfig    $wp 0 -weight 1
    set w
}

    pack [panedwindow .pw -sashwidth 3] -fill both -expand 1
    set t [frame .pw.t]
    set g(canvas) [scrolled_canvas $t.c]

    set f [frame .pw.f]

    .pw add $f -width 300
    .pw add $t -width 600