pack(3tk) Tk Built-In Commands pack(3tk)
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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 children of a parent by packing them in order
around the edges of the parent. The pack command can have any of sev-
eral forms, depending on the option argument:
pack window ?window ...? ?options?
If the first argument to pack is a window name (any value start-
ing 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 win-
dows 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 par-
cel. 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 con-
sume 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 dimen-
sions, 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 en-
tire 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 pad-
ding as specified by -pady).
both Stretch the content both horizontally and verti-
cally.
-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 sepa-
rately. 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 sepa-
rately. 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 geome-
try 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 con-
tainer 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 propa-
gation is enabled for container, which must be a window name
(see GEOMETRY PROPAGATION below). If boolean has a false bool-
ean value then propagation is disabled for container. In either
of these cases an empty string is returned. If boolean is omit-
ted then the command returns 0 or 1 to indicate whether propaga-
tion 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 or-
der 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 win-
dows called the packing list. The -in, -after, and -before configura-
tion 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 rec-
tangular 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 re-
quested height plus twice its -ipady option. However, if the
-fill option is x or both then the width of the content is ex-
panded 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 con-
tent is smaller than the parcel then the -anchor option deter-
mines 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 sub-
tracted 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 be-
comes 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 expand-
able 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 ex-
actly 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 con-
tainer. 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
Tk 4.0 pack(3tk)
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