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pack(3) |
User Contributed Perl Documentation |
pack(3) |
Tk::pack - Geometry manager that packs around edges of cavity
$widget->pack?(args)?
$widget->packOption?(args)?
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
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.
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.
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.
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.
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.
Tk::form Tk::grid Tk::place
geometry manager, location, packer, parcel, propagation, size
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