distToLine

triangleArea x0 y0 x1 y1 x2 y2: returns area of triangle

Intended to detect impossible shearing situation

obj inscope canvaseditor proc distToLine {x0 y0 x1 y1 x2 y2} {
  # calc distance of dot (x2 y2) to line (x0 y0 x1 y1)
  if {
    ($x0 == $x1 && $y0 == $y1) ||
    ($x2 == $x1 && $y2 == $y1) ||
    ($x0 == $x2 && $y0 == $y2)
  } then {
    return 0.0
  }
  set phi [expr {-(atan2($y1-$y0, $x1-$x0))}]
  lappend triangle\
    {*}[rotate $x0 $y0 $phi $x0 $y0]\
    {*}[rotate $x1 $y1 $phi $x0 $y0]\
    {*}[rotate $x2 $y2 $phi $x0 $y0]
  lassign $triangle left - right - - -
  set width [expr {abs($left - $right)}]
  lassign $triangle - bottom - - - top
  set height [expr {abs ($top - $bottom)}]
}