NAME¶
Tk::grid - Geometry manager that arranges widgets in a grid
SYNOPSIS¶
$widget->
grid?(?
widget ...,? ?
arg ?...>?)?
$widget->
gridOption?(
arg
?,
arg ...?)?
DESCRIPTION¶
The
grid method is used to communicate with the grid geometry manager
that arranges widgets in rows and columns inside of another window, called the
geometry master (or master window). The
grid method can have any of
several forms, depending on the
option argument:
- $slave->grid(?$slave,
...??, options?)
- The arguments consist of the optional references to more
slave windows followed by pairs of arguments that specify how to manage
the slaves. The characters -, x and ^, can be
specified instead of a window reference to alter the default location of a
$slave, as described in "RELATIVE
PLACEMENT", below.
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.
The following options are supported:
- -column => n
- Insert the $slave so that it occupies
the nth column in the grid. Column numbers start with 0. If this
option is not supplied, then the $slave is arranged
just to the right of previous slave specified on this call to grid,
or column "0" if it is the first slave. For each x that
immediately precedes the $slave, the column position
is incremented by one. Thus the x represents a blank column for
this row in the grid.
- -columnspan => n
- Insert the slave so that it occupies n columns in
the grid. The default is one column, unless the window name is followed by
a -, in which case the columnspan is incremented once for each
immediately following -.
- -in => $other
- Insert the slave(s) in the master window given by
$other. The default is the first slave's parent
window.
- -ipadx => amount
- The amount specifies how much horizontal internal
padding to leave on each side of the slave(s). This is space is added
inside the slave(s) border. The amount must be a valid screen
distance, such as 2 or '.5c'. It defaults to 0.
- -ipady => amount
- The amount specifies how much vertical internal
padding to leave on on the top and bottom of the slave(s). This space is
added inside the slave(s) border. The amount defaults to 0.
- -padx => amount
- The amount specifies how much horizontal external
padding to leave on each side of the slave(s), in screen units. The
amount defaults to 0. This space is added outside the slave(s)
border.
- -pady => amount
- The amount specifies how much vertical external
padding to leave on the top and bottom of the slave(s), in screen units.
The amount defaults to 0. This space is added outside the slave(s)
border.
- -row => n
- Insert the slave so that it occupies the nth row in
the grid. Row numbers start with 0. If this option is not supplied, then
the slave is arranged on the same row as the previous slave specified on
this call to grid, or the first unoccupied row if this is the first
slave.
- -rowspan => n
- Insert the slave so that it occupies n rows in the
grid. The default is one row. If the next grid method contains
^ characters instead of $slaves that line up
with the columns of this $slave, then the
rowspan of this $slave is extended by
one.
- -sticky => style
- If a slave's cell is larger than its requested dimensions,
this option may be used to position (or stretch) the slave within its
cell. Style is a string that contains zero or more of the
characters n, s, e or w. The string can
optionally contain spaces or commas, but they are ignored. Each letter
refers to a side (north, south, east, or west) that the slave will
"stick" to. If both n and s (or e and
w) are specified, the slave will be stretched to fill the entire
height (or width) of its cavity. The sticky option subsumes the
combination of -anchor and -fill that is used by pack. The
default is '', which causes the slave to be centered in its cavity,
at its requested size.
- $master->gridBbox(?column,
row,? ? column2, row2?)
- With no arguments, the bounding box (in pixels) of the grid
is returned. The return value consists of 4 integers. The first two are
the pixel offset from the master window (x then y) of the top-left corner
of the grid, and the second two integers are the width and height of the
grid, also in pixels. If a single column and row is
specified on the command line, then the bounding box for that cell is
returned, where the top left cell is numbered from zero. If both
column and row arguments are specified, then the bounding
box spanning the rows and columns indicated is returned.
- $master->gridColumnconfigure(index?,
-option=>value, ...?)
- Query or set the column properties of the index
column of the geometry master, $master. The valid
options are -minsize, -weight and -pad. If one or
more options are provided, then index may be given as a list of
column indices to which the configuration options will operate on. The
-minsize option sets the minimum size, in screen units, that will
be permitted for this column. The -weight option (an integer value)
sets the relative weight for apportioning any extra spaces among columns.
A weight of zero (0) indicates the column will not deviate from its
requested size. A column whose weight is two will grow at twice the rate
as a column of weight one when extra space is allocated to the layout. The
-uniform option, when a non-empty value is supplied, places the
column in a uniform group with other columns that have the
same value for -uniform. The space for columns belonging to a
uniform group is allocated so that their sizes are always in strict
proportion to their -weight values. See THE GRID ALGORITHM
below for further details. The -pad option specifies the number of
screen units that will be added to the largest window contained completely
in that column when the grid geometry manager requests a size from the
containing window. If only an option is specified, with no value, the
current value of that option is returned. If only the master window and
index is specified, all the current settings are returned in an list of
"-option value" pairs.
- $slave->gridConfigure(?$slave,
...?, options?)
- The same as grid method.
- $slave->gridForget?($slave,
...)?
- Removes each of the $slaves from grid
for its master and unmaps their windows. The slaves will no longer be
managed by the grid geometry manager. The configuration options for that
window are forgotten, so that if the slave is managed once more by the
grid geometry manager, the initial default settings are used.
- $slave->gridInfo
- Returns a list whose elements are the current configuration
state of the slave given by $slave in the same
option-value form that might be specified to gridConfigure. The
first two elements of the list are ``
-in=>$master'' where
$master is the slave's master.
- $master->gridLocation(x,
y)
- Given x and y values in screen units relative
to the master window, the column and row number at that x and
y location is returned. For locations that are above or to the left
of the grid, -1 is returned.
- $master->gridPropagate?(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 method returns 0
or 1 to indicate whether propagation is currently enabled for
$master. Propagation is enabled by default.
- $master->gridRowconfigure(index?,
-option=>value, ...?)
- Query or set the row properties of the index row of
the geometry master, $master. The valid options are
-minsize, -weight and -pad. If one or more options
are provided, then index may be given as a list of row indeces to
which the configuration options will operate on. The -minsize
option sets the minimum size, in screen units, that will be permitted for
this row. The -weight option (an integer value) sets the relative
weight for apportioning any extra spaces among rows. A weight of zero (0)
indicates the row will not deviate from its requested size. A row whose
weight is two will grow at twice the rate as a row of weight one when
extra space is allocated to the layout. The -uniform option, when a
non-empty value is supplied, places the row in a uniform group with
other rows that have the same value for -uniform. The space for
rows belonging to a uniform group is allocated so that their sizes are
always in strict proportion to their -weight values. See THE
GRID ALGORITHM below for further details. The -pad option
specifies the number of screen units that will be added to the largest
window contained completely in that row when the grid geometry manager
requests a size from the containing window. If only an option is
specified, with no value, the current value of that option is returned. If
only the master window and index is specified, all the current settings
are returned in an list of "option-value" pairs.
- $slave->gridRemove?($slave,
...)?
- Removes each of the $slaves from grid
for its master and unmaps their windows. The slaves will no longer be
managed by the grid geometry manager. However, the configuration options
for that window are remembered, so that if the slave is managed once more
by the grid geometry manager, the previous values are retained.
- $master->gridSize
- Returns the size of the grid (in columns then rows) for
$master. The size is determined either by the
$slave occupying the largest row or column, or the
largest column or row with a -minsize, -weight, or
-pad that is non-zero.
- $master->gridSlaves?(-option=>value)?
- If no options are supplied, a list of all of the slaves in
$master are returned, most recently manages first.
-option can be either -row or -column which causes
only the slaves in the row (or column) specified by value to be
returned.
RELATIVE PLACEMENT¶
The
grid method contains a limited set of capabilities that permit
layouts to be created without specifying the row and column information for
each slave. This permits slaves to be rearranged, added, or removed without
the need to explicitly specify row and column information. When no column or
row information is specified for a
$slave, default values
are chosen for
-column,
-row,
-columnspan and
-rowspan at the time the
$slave is managed. The
values are chosen based upon the current layout of the grid, the position of
the
$slave relative to other
$slaves
in the same grid method, and the presence of the characters
-,
^, and
^ in
grid method where
$slave
names are normally expected.
- -
- This increases the columnspan of the
$slave to the left. Several -'s in a row will
successively increase the columnspan. A - may not follow a ^
or a x.
- x
- This leaves an empty column between the
$slave on the left and the
$slave on the right.
- ^
- This extends the -rowspan of the
$slave above the ^'s in the grid. The number
of ^'s in a row must match the number of columns spanned by the
$slave above it.
THE GRID ALGORITHM¶
The grid geometry manager lays out its slaves in three steps. In the first step,
the minimum size needed to fit all of the slaves is computed, then (if
propagation is turned on), a request is made of the master window to become
that size. In the second step, the requested size is compared against the
actual size of the master. If the sizes are different, then space is added to
or taken away from the layout as needed. For the final step, each slave is
positioned in its row(s) and column(s) based on the setting of its
sticky flag.
To compute the minimum size of a layout, the grid geometry manager first looks
at all slaves whose columnspan and rowspan values are one, and computes the
nominal size of each row or column to be either the
minsize for that
row or column, or the sum of the
padding plus the size of the largest
slave, whichever is greater. Then the slaves whose rowspans or columnspans are
greater than one are examined. If a group of rows or columns need to be
increased in size in order to accommodate these slaves, then extra space is
added to each row or column in the group according to its
weight. For
each group whose weights are all zero, the additional space is apportioned
equally.
When multiple rows or columns belong to a uniform group, the space allocated to
them is always in proportion to their weights. (A weight of zero is considered
to be 1.) In other words, a row or column configured with
-weight 1
-uniform a will have exactly the same size as any other row or column
configured with
-weight 1 -uniform a. A row or column configured with
-weight 2 -uniform b will be exactly twice as large as one that is
configured with
-weight 1 -uniform b.
More technically, each row or column in the group will have a size equal to
k*weight for some constant k. The constant k is chosen so that no row
or column becomes smaller than its minimum size. For example, if all rows or
columns in a group have the same weight, then each row or column will have the
same size as the largest row or column in the group.
For masters whose size is larger than the requested layout, the additional space
is apportioned according to the row and column weights. If all of the weights
are zero, the layout is centered within its master. For masters whose size is
smaller than the requested layout, space is taken away from columns and rows
according to their weights. However, once a column or row shrinks to its
minsize, its weight is taken to be zero. If more space needs to be removed
from a layout than would be permitted, as when all the rows or columns are at
there minimum sizes, the layout is clipped on the bottom and right.
GEOMETRY PROPAGATION¶
The grid geometry manager 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
gridPropagate method may be used to turn off propagation for one or
more masters. If propagation is disabled then grid will not set the requested
width and height of the master window. 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. In addition, all
slaves in one call to
grid must have the same master.
STACKING 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 managed
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.
CREDITS¶
The
grid method is based on ideas taken from the
GridBag geometry
manager written by Doug. Stein, and the
blt_table geometry manager,
written by George Howlett.
SEE ALSO¶
Tk::form Tk::pack Tk::place
KEYWORDS¶
geometry manager, location, grid, cell, propagation, size, pack, master,
slave