Provided by: perl-tk_804.031-1build1_amd64 
NAME
Tk::pack - Geometry manager that packs around edges of cavity
SYNOPSIS
$widget->pack?(args)?
$widget->packOption?(args)?
DESCRIPTION
The pack method 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.
In this perl port of Tk it is normal to pack widgets one-at-a-time using the widget object
to be packed to invoke a method call. This is a slight distortion of underlying Tk
interface (which can handle lists of windows to one pack method call) but has proven
effective in practice.
The pack method can have any of several forms, depending on Option:
$slave->pack?(options)?
The options consist of pairs of arguments that specify how to manage the slave. 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 be another window. Use its master as the master for the slave,
and insert the slave 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 be another window. Use its master as the master for the slave,
and insert the slave just before $other in the packing order.
-expand => boolean
Specifies whether the slave 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.
-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 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 padding as specified by -pady).
both Stretch the slave both horizontally and vertically.
-in => $master
Insert the slave(s) at the end of the packing order for the master window
given by $master.
-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 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 left, right, top, or bottom. Defaults to top.
If no -in, -after or -before option is specified then slave 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 slave will be
inserted at the specified point. If the slave are already managed by the geometry manager
then any unspecified options for them retain their previous values rather than receiving
default values.
$slave->packConfigure?(options)?
Same as pack.
$slave->packForget
Removes slave from the packing order for its master and unmaps its window. The slave
will no longer be managed by the packer.
$slave->packInfo
Returns a list whose elements are the current configuration state of the slave given
by $slave in the same option-value form that might be specified to packConfigure. The
first two elements of the list are ``-in=>$master'' where $master is the slave's
master.
$master->packPropagate?(boolean)?
If boolean has a true boolean value such as 1 or on then propagation is enabled for
$master, (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 method returns 0 or 1 to indicate whether
propagation is currently enabled for $master. Propagation is enabled by default.
$master->packSlaves
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 list/string is returned in array/scalar context,
respectively
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 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 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 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 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 packPropagate method 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. 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 methods to change the stacking order of either the master or the slave.
SEE ALSO
Tk::form Tk::grid Tk::place
KEYWORDS
geometry manager, location, packer, parcel, propagation, size