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 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 slave ?slave ...? ?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 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 con-
sume 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 dimen-
sions, 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 pad-
ding as specified by -pady).
both Stretch the slave both horizontally and verti-
cally.
-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 sepa-
rately. 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 sepa-
rately. 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 pre-
vious 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 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 propa-
gation 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.
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 cav-
ity; 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 sub-
tracted from the cavity, leaving a smaller rectangular cavity for the
next slave. If a slave doesn't 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 dis-
tributed 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 dis-
tributed 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 infor-
mation 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. Other-
wise the master will obscure the slave and it will appear as if the
slave hasn't 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)
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