NAME¶
pack - Geometry manager that packs around edges of cavity
SYNOPSIS¶
pack 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 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 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 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 separately.
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 separately. 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
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 configuration
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 master.
- 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 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 does not 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
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. Otherwise the master
will obscure the slave and it will appear as if the slave has not 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(3tk), place(3tk)
KEYWORDS¶
geometry manager, location, packer, parcel, propagation, size