shearHobject

$dot dot shearHobject x y x0 y0 BotY mode: moves dot according to horizontal shear containg object interactively

obj method dot shearHobject {x y x0 y0 BotY {mode parallel}} {
  lappend transformL\
    shearHorizontal [list $BotY $y0 [- $x $x0]]
  if {$mode ne "parallel"} then {
    set fac [expr {($y - $BotY) / ($y0 - $BotY)}]
    lappend transformL scaleVertical [list $BotY $fac]
  }
  $self transform {*}$transformL
}