Provided by: tk8.6-doc_8.6.13-2_all 
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 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:
pack window ?window ...? ?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 window ?window ...? ?options?
The arguments consist of the names of one or more content windows followed by pairs
of arguments that specify how to manage the content. 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 container as the container
for the content, and insert the content 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 content in its parcel. Defaults to center.
-before other
Other must the name of another window. Use its container as the container
for the content, and insert the content just before other in the packing
order.
-expand boolean
Specifies whether the content should be expanded to consume extra space in
their container. Boolean may have any proper boolean value, such as 1 or
no. Defaults to 0.
-fill style
If a content's parcel is larger than its requested dimensions, this option
may be used to stretch the content. Style must have one of the following
values:
none Give the content its requested dimensions plus any internal padding
requested with -ipadx or -ipady. This is the default.
x Stretch the content horizontally to fill the entire width of its
parcel (except leave external padding as specified by -padx).
y Stretch the content vertically to fill the entire height of its
parcel (except leave external padding as specified by -pady).
both Stretch the content both horizontally and vertically.
-in container
Insert the window at the end of the packing order for the container window
given by container.
-ipadx amount
Amount specifies how much horizontal internal padding to leave on each side
of the content. 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 content. Amount defaults to 0.
-padx amount
Amount specifies how much horizontal external padding to leave on each side
of the content. 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 content. 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 container the content 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 content 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 content will be inserted at the specified point. If any
of the content are already managed by the geometry manager then any unspecified
options for them retain their previous values rather than receiving default values.
pack forget window ?window ...?
Removes each of the windows from the packing order for its container and unmaps
their windows. The content will no longer be managed by the packer.
pack info window
Returns a list whose elements are the current configuration state of the window
given by window in the same option-value form that might be specified to pack
configure. The first two elements of the list are “-in container” where container
is the window's container.
pack propagate container ?boolean?
If boolean has a true boolean value such as 1 or on then propagation is enabled for
container, which must be a window name (see GEOMETRY PROPAGATION below). If
boolean has a false boolean value then propagation is disabled for container. 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
container. Propagation is enabled by default.
pack slaves window
Returns a list of all of the content windows in the packing order for window. The
order of the content windows in the list is the same as their order in the packing
order. If window has no content then an empty string is returned. │
pack content window │
Synonym for pack slaves window.
THE PACKER ALGORITHM
For each container the packer maintains an ordered list of content windows called the
packing list. The -in, -after, and -before configuration options are used to specify the
container for each content and the content's position in the packing list. If none of
these options is given for a content then the content is added to the end of the packing
list for its parent.
The packer arranges the content windows for a container by scanning the packing list in
order. At the time it processes each content, a rectangular area within the container is
still unallocated. This area is called the cavity; for the first content it is the
entire area of the container.
For each content the packer carries out the following steps:
[1] The packer allocates a rectangular parcel for the content along the side of the
cavity given by the content'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 content 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 content 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 content. The width will normally be the
content's requested width plus twice its -ipadx option and the height will normally
be the content's requested height plus twice its -ipady option. However, if the
-fill option is x or both then the width of the content 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 content is expanded to fill the width of the parcel,
minus twice the -pady option.
[3] The packer positions the content over its parcel. If the content is smaller than
the parcel then the -anchor option determines where in the parcel the content will
be placed. If -padx or -pady is non-zero, then the given amount of external
padding will always be left between the content and the edges of the parcel.
Once a given content has been packed, the area of its parcel is subtracted from the
cavity, leaving a smaller rectangular cavity for the next content. If a content does not
use all of its parcel, the unused space in the parcel will not be used by subsequent
content. If the cavity should become too small to meet the needs of a content then the
content will be given whatever space is left in the cavity. If the cavity shrinks to zero
size, then all remaining content on the packing list will be unmapped from the screen
until the container window becomes large enough to hold them again.
EXPANSION
If a container window is so large that there will be extra space left over after all of
its content have been packed, then the extra space is distributed uniformly among all of
the content for which the -expand option is set. Extra horizontal space is distributed
among the expandable content whose -side is left or right, and extra vertical space is
distributed among the expandable content whose -side is top or bottom.
GEOMETRY PROPAGATION
The packer normally computes how large a container must be to just exactly meet the needs
of its content, and it sets the requested width and height of the container 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 containers. 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 container window to have a fixed size that you specify.
RESTRICTIONS ON CONTAINER WINDOWS
The container for each content must either be the content's parent (the default) or a
descendant of the content's parent. This restriction is necessary to guarantee that the
content can be placed over any part of its container that is visible without danger of the
content being clipped by its parent.
PACKING ORDER
If the container for a content is not its parent then you must make sure that the content
is higher in the stacking order than the container. Otherwise the container will obscure
the content and it will appear as if the content has not been packed correctly. The
easiest way to make sure the content is higher than the container is to create the
container 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 container or the content.
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(3tk), place(3tk)
KEYWORDS
geometry manager, location, packer, parcel, propagation, size