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  4. pack(n)

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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 command 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 command can have any
    of several forms, depending on the option argument:



  

  
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.

  

  
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:







  

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

  

  
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.

  

  
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.

  

  
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:







  

  
Give the slave its requested dimensions plus any internal padding
      requested with -ipadx or -ipady. This is the default.

  

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

  

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

  

  
Stretch the slave both horizontally and vertically.







  

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

  

  
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.

  

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

  

  
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.

  

  
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.

  

  
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.





  

  
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.

  

  
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 elements of the list are
      “-in master” where master is the
      slave's master.

  

  
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 propagation
      is currently enabled for master. Propagation is enabled by
    default.

  

  
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 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 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 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
.mid insert end "This layout is like Java's BorderLayout"
# 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







  

    4.0
    Tk