|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:
|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 elements of the list are -in master where master is the slaves 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 propagation 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.|
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 slaves 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:
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.
 The packer allocates a rectangular parcel for the slave along the side of the cavity given by the slaves -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)  The packer chooses the dimensions of the slave. The width will normally be the slaves requested width plus twice its -ipadx option and the height will normally be the slaves 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.  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.
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.
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.
The master for each slave must either be the slaves parent (the default) or a descendant of the slaves 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.
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.
# 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 Javas 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
geometry manager, location, packer, parcel, propagation, size