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
