constraint

Constraints are items located in option -constraint.

$group constraint: returns list of constraints
$group constraint noprint: returns yes if noprint is set, otherwise returns no
$group constraint noprint yes: sets constraint noprint

These constraints are realized:

noprint: suppress printing of object if used for internal purposes only
size: suppress scaling
orient: suppress rotating
shear: suppress shearing horizontal, vertical, but not diagonal
fillcolor: fix color of fill objects
linecolor: fix color of line objects
linewidth: fix width of line objects
gravity: preferring objecs for some purposes

obj method group constraint {{what {}} {how info}} {
  set constr [$self cget -constraint]
  if {$what eq ""} then {
    set constr
  } elseif {$how eq "info"} then {
    expr {$what in [$self cget -constraint] ? yes : no}
  } elseif {$how eq "toggle"} then {
    if {[$self constraint $what]} then {
      $self constraint $what no
    } else {
      $self constraint $what yes
    }
  } elseif {$how} then {
    if {$what ni $constr} then {
      lappend constr $what
      $self configure -constraint $constr
    }
  } else {
    set index [lsearch $constr $what]
    $self configure -constraint [lreplace $constr $index $index]
  }
}