NAME
Prima::Widget::pack - Geometry manager that packs around edges of
cavity
SYNOPSIS
$widget-> pack( args);
$widget-> packInfo( args);
$widget-> geometry( gt::Pack);
DESCRIPTION
The pack method is used to communicate with the packer, a geometry
manager that arranges the children of a owner by packing them in order
around the edges of the owner.
In this port of Tk::pack 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 the original Tcl-Tk interface (which can handle
lists of windows to one pack method call) but Tk reports that it has
proven effective in practice.
The pack method can have any of several forms, depending on Option:
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. Currently, only the
immediate owner can be accepted as 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 owner 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.
packForget
Removes slave from the packing order for its master and unmaps its
window. The slave will no longer be managed by the packer.
packInfo [ %OPTIONS ]
In get-mode, returns a list whose elements are the current
configuration state of the slave given by $slave. The first two
elements of the list are ‘‘in=>$master’’ where $master is the
slave’s master.
In set-mode, sets all pack parameters, but does not set widget
geometry property to "gt::Pack".
packPropagate BOOLEAN
If boolean has a true boolean value then propagation is enabled for
$master, (see "Geometry propagation" below). If boolean has a
false boolean value then propagation is disabled for $master. 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.
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 owner.
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:
· 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)
· 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.
· 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 geometryPropagate 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 not be a child of the slave, and must
not be present in any other list of slaves that directly or indirectly
refers to the slave.
Packing order
If the master for a slave is not its owner 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 bring_to_front and send_to_back methods to change
the stacking order of either the master or the slave.
SEE ALSO
Prima, Prima::Widget
Tk::pack Tk::place