pack(n) Tk Built-In Commands pack(n)_________________________________________________________________NAMEpack - Geometry manager that packs around edges of cavity
SYNOPSISpack 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:
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:
-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 cen-
ter.
-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 consume extra space in their
master. Boolean may have any proper boolean
value, such as 1 or no. Defaults to 0.
Tk 4.0 1
pack(n) Tk Built-In Commands pack(n)-fill style
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:
none Give the slave its requested dimen-
sions 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 padding as
specified by -pady).
both Stretch the slave both horizontally
and vertically.
-in other
Insert the slave(s) at the end of the pack-
ing order for the master window given by
other.
-ipadx amount
Amount specifies how much horizontal inter-
nal 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 exter-
nal padding to leave on each side of the
slave(s). Amount defaults to 0.
-pady amount
Amount specifies how much vertical external
padding to leave on each side of the
slave(s). Amount defaults to 0.
-side side
Specifies which side of the master the
slave(s) will be packed against. Must be
Tk 4.0 2
pack(n) Tk Built-In Commands pack(n)
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.
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 con-
figuration 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 mas-
ter.
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.
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 mas-
ter 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
Tk 4.0 3
pack(n) Tk Built-In Commands pack(n)
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 unal-
located. 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 rectangu-
lar 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.
Tk 4.0 4
pack(n) Tk Built-In Commands pack(n)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 dimen-
sions. 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 par-
ent (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 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.
KEYWORDS
geometry manager, location, packer, parcel, propagation,
size
Tk 4.0 5
