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pack(n)			     Tk	Built-In Commands		       pack(n)

NAME
       pack - Geometry manager that packs around edges of cavity

SYNOPSIS
       (pack option arg	?arg ...?)

DESCRIPTION
       The  pack  procedure is used to communicate with	the packer, a geometry
       manager that arranges the children of a parent by packing them in order
       around  the  edges  of  the parent.  The	pack procedure can have	any of
       several forms, depending	on the option argument:

       (pack slave ?slave ...? ?options?)
	      If the first argument to pack is a window	name (any value	start-
	      ing with ``.''), then the	procedure is processed in the same way
	      as pack configure.

       (pack 'configure	slave ?slave ...? ?options?)
	      The arguments consist of the names of one	or more	slave  windows
	      followed	by  pairs  of arguments	that specify how to manage the
	      slaves.  See ``THE PACKER	ALGORITHM'' below for details  on  how
	      the  options  are	used by	the packer.  The following options are
	      supported:

	      :after other
		     Other must	the name of another window.  Use its master as
		     the master	for the	slaves,	and insert the slaves just af-
		     ter other in the packing order.

	      :anchor anchor
		     Anchor must be a valid anchor position such as n  or  sw;
		     it	 specifies where to position each slave	in its parcel.
		     Defaults to center.

	      :before other
		     Other must	the name of another window.  Use its master as
		     the master	for the	slaves,	and insert the slaves just be-
		     fore other	in the packing order.

	      :expand boolean
		     Specifies whether the slaves should be expanded  to  con-
		     sume  extra  space	in their master.  Boolean may have any
		     proper boolean value. Defaults to #f.

	      :fill style
		     If	a slave's parcel is larger than	its  requested	dimen-
		     sions,  this  option  may	be  used to stretch the	slave.
		     Style must	have one of the	following values:

		     none   Give the slave its requested dimensions  plus  any
			    internal  padding requested	with :ipadx or :ipady.
			    This is the	default.

		     x	    Stretch the	slave horizontally to fill the	entire
			    width of its parcel	(except	leave external padding
			    as specified by :padx).

		     y	    Stretch the	slave vertically to  fill  the	entire
			    height  of	its parcel (except leave external pad-
			    ding as specified by :pady).

		     both   Stretch the	slave  both  horizontally  and	verti-
			    cally.

	      :in other
		     Insert  the  slave(s) at the end of the packing order for
		     the master	window given by	other.

	      :ipadx amount
		     Amount specifies how much horizontal internal padding  to
		     leave  on	each  side  of the slave(s).  Amount must be a
		     valid screen distance, such as 2 or .5c.  It defaults  to
		     0.

	      :ipady amount
		     Amount  specifies	how  much vertical internal padding to
		     leave on each side	of the slave(s).  Amount  defaults  to
		     0.

	      :padx amount
		     Amount  specifies how much	horizontal external padding to
		     leave on each side	of the slave(s).  Amount  defaults  to
		     0.

	      :pady amount
		     Amount  specifies	how  much vertical external padding to
		     leave on each side	of the slave(s).  Amount  defaults  to
		     0.

	      :side side
		     Specifies	which  side of the master the slave(s) will be
		     packed against.  Must be left,  right,  top,  or  bottom.
		     Defaults to top.

	      If  no  :in,  :after or :before option is	specified then each of
	      the slaves will be inserted at the end of	the packing  list  for
	      its  parent unless it is already managed by the packer (in which
	      case it will be left where it is).  If one of these  options  is
	      specified	 then all the slaves will be inserted at the specified
	      point.  If any of	the slaves are already managed by the geometry
	      manager  then any	unspecified options for	them retain their pre-
	      vious values rather than receiving default values.

       (pack 'forget slave ?slave ...?)
	      Removes each of the slaves from the packing order	for its	master
	      and  unmaps their	windows.  The slaves will no longer be managed
	      by the packer.

       (pack 'info slave)
	      Returns a	list whose  elements  are  the	current	 configuration
	      state  of	the slave given	by slave in the	same option-value form
	      that might be specified to pack configure.  The first  two  ele-
	      ments of the list	are ``:in master'' where master	is the slave's
	      master.

       (pack 'propagate	master ?boolean?)
	      If boolean has a true boolean value such as 1 or on then	propa-
	      gation  is  enabled for master, which must be a window name (see
	      ``GEOMETRY PROPAGATION'' below).	If boolean has a false boolean
	      value  then  propagation	is  disabled for master.  In either of
	      these cases an empty string is returned.	If boolean is  omitted
	      then the procedure returns #f or #t to indicate whether propaga-
	      tion is currently	enabled	for master.  Propagation is enabled by
	      default.

       (pack 'slaves master)
	      Returns  a  list	of  all	of the slaves in the packing order for
	      master.  The order of the	slaves in the  list  is	 the  same  as
	      their  order in the packing order.  If master has	no slaves then
	      an empty string is returned.

THE PACKER ALGORITHM
       For each	master the packer maintains an ordered list of	slaves	called
       the  packing  list.  The	:in, :after, and :before configuration options
       are used	to specify the master for each slave and the slave's  position
       in  the	packing	 list.	 If none of these options is given for a slave
       then the	slave is added to the end of the packing list for its parent.

       The packer arranges the slaves for a master  by	scanning  the  packing
       list in order.  At the time it processes	each slave, a rectangular area
       within the master is still unallocated.	This area is called  the  cav-
       ity;  for the first slave it is the entire area of the master.

       For each	slave the packer carries out the following steps:

       [1]    The  packer  allocates  a	rectangular parcel for the slave along
	      the side of the cavity given by the slave's  :side  option.   If
	      the  side	 is  top or bottom then	the width of the parcel	is the
	      width of the cavity and its height is the	 requested  height  of
	      the  slave  plus	the :ipady and :pady options.  For the left or
	      right side the height of the parcel is the height	of the	cavity
	      and  the	width  is  the	requested  width of the	slave plus the
	      :ipadx and :padx options.	 The parcel may	 be  enlarged  further
	      because of the :expand option (see ``EXPANSION'' below)

       [2]    The  packer chooses the dimensions of the	slave.	The width will
	      normally be the slave's requested	width plus  twice  its	:ipadx
	      option  and  the	height	will normally be the slave's requested
	      height plus twice	its :ipady option.  However, if	the :fill  op-
	      tion  is	x  or  both then the width of the slave	is expanded to
	      fill the width of	the parcel, minus twice	the :padx option.   If
	      the  :fill  option  is y or both then the	height of the slave is
	      expanded to fill the width of the	parcel,	minus twice the	 :pady
	      option.

       [3]    The packer positions the slave over its parcel.  If the slave is
	      smaller than the parcel then the :anchor option determines where
	      in  the  parcel  the slave will be placed.  If :padx or :pady is
	      non-zero,	then the given amount of external padding will	always
	      be left between the slave	and the	edges of the parcel.

       Once  a	given  slave  has  been	packed,	the area of its	parcel is sub-
       tracted from the	cavity,	leaving	a smaller rectangular cavity  for  the
       next slave.  If a slave doesn't use all of its parcel, the unused space
       in the parcel will not be used by subsequent  slaves.   If  the	cavity
       should  become  too  small  to meet the needs of	a slave	then the slave
       will be given whatever space is left in	the  cavity.   If  the	cavity
       shrinks	to  zero  size,	 then all remaining slaves on the packing list
       will be unmapped	from the screen	until the master window	becomes	 large
       enough to hold them again.

EXPANSION
       If a master window is so	large that there will be extra space left over
       after all of its	slaves have been packed, then the extra	space is  dis-
       tributed	uniformly among	all of the slaves for which the	:expand	option
       is set.	Extra horizontal space is  distributed	among  the  expandable
       slaves  whose  :side is left or right, and extra	vertical space is dis-
       tributed	among the expandable slaves whose :side	is top or bottom.

GEOMETRY PROPAGATION
       The packer normally computes how	large a	master must be to just exactly
       meet  the  needs	 of  its  slaves,  and it sets the requested width and
       height of the master to these dimensions.  This causes geometry	infor-
       mation to propagate up through a	window hierarchy to a top-level	window
       so that the entire sub-tree sizes itself	to fit the needs of  the  leaf
       windows.	 However, the pack propagate procedure may be used to turn off
       propagation for one or more masters.  If	propagation is	disabled  then
       the  packer  will not set the requested width and height	of the packer.
       This may	be useful if, for example, you wish for	 a  master  window  to
       have a fixed size that you specify.

RESTRICTIONS ON	MASTER WINDOWS
       The  master  for	 each slave must either	be the slave's parent (the de-
       fault) or a descendant of the slave's parent.  This restriction is nec-
       essary  to  guarantee that the slave can	be placed over any part	of its
       master that is visible without danger of	the slave being	clipped	by its
       parent.

PACKING	ORDER
       If  the	master	for  a slave is	not its	parent then you	must make sure
       that the	slave is higher	in the stacking	order than the master.	Other-
       wise  the  master  will	obscure	the slave and it will appear as	if the
       slave hasn't been packed	correctly.  The	easiest	way to make  sure  the
       slave  is  higher than the master is to create the master window	first:
       the most	recently created window	will be	highest	in the stacking	order.
       Or,  you	 can use the raise and lower procedures	to change the stacking
       order of	either the master or the slave.

SEE ALSO
       grid, place

STk				      3.1			       pack(n)

NAME | SYNOPSIS | DESCRIPTION | THE PACKER ALGORITHM | EXPANSION | GEOMETRY PROPAGATION | RESTRICTIONS ON MASTER WINDOWS | PACKING ORDER | SEE ALSO

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