## grid

Geometry manager that arranges widgets in a grid

### SYNOPSIS

(grid option arg ?arg ...?)

### DESCRIPTION

The grid procedure 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 procedure can have any of several forms, depending on the option argument:

(grid slave ?slave ...? ?options?)
  If the first argument to grid is a window name (any value starting with ``.''), then the procedure is processed in the same way as grid configure.

(grid 'bbox master)
(grid 'bbox master column row)
(grid 'bbox master 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.

(grid 'columnconfigure master 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 indexes 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 :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.

(grid '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. The characters :, x and ^, can be specified instead of a window name to alter the default location of a slave, as described in the ``RELATIVE PLACEMENT'' section, below. 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 procedure 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 contains 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 the empty string, which causes the slave to be centered in its cavity, at its requested size.

  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.

(grid 'forget slave ?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.

(grid '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 grid configure. The first two elements of the list are ``:in master'' where master is the slave's master.

(grid 'location master 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.

(grid 'propagate master)
(grid 'propagate master boolean)
  If boolean has a true boolean value 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 list is returned. If boolean is omitted then the procedure returns #f or #t to indicate whether propagation is currently enabled for master. Propagation is enabled by default.

(grid 'rowconfigure master index )
(grid 'rowconfigure master 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 :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.

(grid 'remove slave ?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.

(grid 'size master)
  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.

(grid 'slaves master)
(grid 'slaves master :option value)
  If no options are supplied, a list of all of the slaves in master are returned, most recently managed 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 procedure 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 procedure, and the presence of the characters :, ^, and ^ in grid procedure 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 spaces 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.

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 grid propagate procedure 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 command 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

pack, place

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