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



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NAME
       pack - Geometry manager that packs around edges of cavity

SYNOPSIS
       pack option arg ?arg ...?
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DESCRIPTION
       The  pack  command is used to communicate with the packer, a geometry manager that arranges the chil-dren children
       dren of a parent by packing them in order around the edges of the parent.  The pack command 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 starting with "."), then the command
              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 after 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 before other in the packing order.

              -expand boolean
                     Specifies whether the slaves should be expanded to consume extra space in their master.
                     Boolean may have any proper boolean value, such as 1 or no.  Defaults to 0.

              -fill style
                     If a slave's parcel is larger than its requested dimensions, 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 padding as specified by -pady).

                     both   Stretch the slave both horizontally and vertically.

              -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  may  be  a list of two values to specify padding for left and right
                     separately.  Amount defaults to 0.

              -pady amount
                     Amount specifies how much vertical external padding  to  leave  on  each  side  of  the
                     slave(s).   Amount  may  be  a list of two values to specify padding for top and bottom
                     separately.  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 previous 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 elements
              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 propagation 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 command returns 0 or 1 to indicate whether  propaga-tion propagation
              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 cavity;  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 cav-ity cavity
              ity 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 option 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 subtracted from the cavity, leaving a
       smaller rectangular cavity for the next slave.  If a slave does not 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 distributed 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 distributed 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
       information to propagate up through a window hierarchy to a top-level window so that the entire  sub-tree subtree
       tree  sizes  itself to fit the needs of the leaf windows.  However, the pack propagate command 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 default)  or  a  descendant  of  the
       slave's  parent.   This  restriction  is necessary 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.  Otherwise the master will obscure the slave and it will appear as if
       the slave has not 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 commands to change the stacking order of  either
       the master or the slave.

EXAMPLE
              # Make the widgets
              label .t -text "This widget is at the top"    -bg red
              label .b -text "This widget is at the bottom" -bg green
              label .l -text "Left\nHand\nSide"
              label .r -text "Right\nHand\nSide"
              text .mid
              # Lay them out
              pack .t   -side top    -fill x
              pack .b   -side bottom -fill x
              pack .l   -side left   -fill y
              pack .r   -side right  -fill y
              pack .mid -expand 1    -fill both


SEE ALSO
       grid(n), place(n)


KEYWORDS
       geometry manager, location, packer, parcel, propagation, size



Tk                                                   4.0                                             pack(n)