N:blt table
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table - Arranges widgets in a table
Contents |
SYNOPSIS
table container ?widget index option value?...
table arrange container
table cget container ?item? option
table configure container ?item?... ?option value?...
table extents container item
table forget widget ?widget?...
table info container item
table locate container x y
table containers ?switch? ?arg?
table save container
table search container ?switch arg?...
DESCRIPTION
The table command arranges widgets in a table. The alignment of widgets is detemined by their row and column
positions and the number of rows or columns that they span.
INTRODUCTION
Probably the most painstaking aspect of building a graphical application is getting the placement and size of the
widgets just right. It usually takes many iterations to align widgets and adjust their spacing. That's because
managing the geometry of widgets is simply not a packing problem, but also graphical design problem. Attributes
such as alignment, symmetry, and balance are more important than minimizing the amount of space used for packing.
The table geometry manager arranges widgets in a table. It's easy to align widgets (horizontally and vertically)
or to create empty space to balance the arrangement of the widgets. Widgets (called slaves in the Tk parlance)
are arranged inside a containing widget (called the master). Widgets are positioned at row,column locations and
may span any number of rows or columns. More than one widget can occupy a single location.
The placement of widget windows determines both the size and arrangement of the table. The table queries the
requested size of each widget. The requested size of a widget is the natural size of the widget (before the wid-
get is shrunk or expanded). The height of each row and the width of each column is the largest widget spanning
that row or column. The size of the table is in turn the sum of the row and column sizes. This is the table's
normal size.
The total number of rows and columns in a table is determined from the indices specified. The table grows dynam-
ically as windows are added at larger indices.
EXAMPLE
The table geometry manager is created by invoking the table command.
# Create a table in the root window
table .
The window . is now the container of the table. Widgets are packed into the table and displayed within the con-
fines of the container.
You add widgets to the table by row and column location. Row and column indices start from zero.
label .title -text "This is a title"
# Add a label to the table
table . .title 0,0
The label .title is added to the table. We can add more widgets in the same way.
button .ok -text "Ok"
button .cancel -text "Cancel"
# Add two buttons
table . .ok 1,0
table . .cancel 1,1
Two buttons .ok and .cancel are now packed into the second row of the table. They each occupy one cell of the
table. By default, widgets span only a single row and column.
The first column contains two widgets, .title and .ok. By default, the widest of the two widgets will define the
width of the column. However, we want .title to be centered horizontally along the top of the table. We can
make .title span two columns using the configure operation.
# Make the label span both columns
table configure . .title -cspan 2
The label .title will now be centered along the top row of the table.
In the above example, we've create and arranged the layout for the table invoking the table command several
times. Alternately, we could have used a single table command.
label .title -text "This is a title"
button .ok -text "Ok"
button .cancel -text "Cancel"
# Create and pack the table
table . \
.title 0,0 -cspan 2 \
.ok 1,0 \
.cancel 1,1
The table will override the requested width and height of the container so that the window fits the table
exactly. This also means that any change to the size of table will be propagated up through the Tk window hier-
archy. This feature can be turned off using the configure operation again.
table configure . -propagate no
You can also set the width of height of the table to a specific value. This supersedes the calculated table size.
# Make the container 4 inches wide, 3 inches high
table configure . -reqwidth 4i -reqheight 3i
If a widget is smaller than the cell(s) it occupies, the widget will float within the extra space. By default,
the widget will be centered within the space, but you can anchor the widget to any side of cell using the -anchor
configuration option.
table configure . .ok -anchor w
The -fill option expands the widget to fill the extra space either vertically or horizontally (or both).
# Make the title label fill the entire top row
table configure . .title -cspan 2 -fill x
# Each button will be as height of the 2nd row.
table configure . .ok .cancel -fill y
The width of .title will be the combined widths of both columns. Both .ok and .cancel will become as tall as the
second row.
The -padx and -pady options control the amount of padding around the widget. Both options take a list of one or
two values.
# Pad the title by two pixels above and below.
table configure . .title -pady 2
# Pad each button 2 pixels on the left, and 4 on the right.
table configure . .ok .cancel -padx { 2 4 }
If the list has only one value, then both exterior sides (top and bottom or left and right) of the widget are
padded by that amount. If the list has two elements, the first specifies padding for the top or left side and
the second for the bottom or right side.
Like the container, you can also override the requested widths and heights of widgets using the -reqwidth and
-reqheight options. This is especially useful with character-based widgets (such as buttons, labels, text, list-
box, etc) that let you specify their size only in units of characters and lines, instead of pixels.
# Make all buttons one inch wide
table configure . .ok .cancel -reqwidth 1i
Each row and column of the table can be configured, again using the configure operation. Rows are and columns
are designated by Ri and Ci respectively, where i is the index of the row or column.
For example, you can set the size of a row or column.
# Make the 1st column 2 inches wide
table configure . c0 -width 2.0i
# Make the 2nd row 1/2 inch high.
table configure . r1 -height 0.5i
The new size for the row or column overrides its calculated size. If no widgets span the row or column, its
height or width is zero. So you can use the -width and -height options to create empty spaces in the table.
# Create an empty row and column
table configure . r2 c2 -width 1i
The -pady option lets you add padding to the top and bottom sides of rows. The -padx option adds padding to the
left and right sides of columns. Both options take a list of one or two values.
# Pad above the title by two pixels
table configure . r0 -pady { 2 0 }
# Pad each column 4 pixels on the left, and 2 on the right.
table configure . c* -padx { 2 4 }
Notice that you can configure all the rows and columns using either R* or C*.
When the container is resized, the rows and columns of the table are also resized. Only the rows or columns that
contain widgets (a widget spans the row or column) grow or shrink. The -resize option indicates whether the row
or column can be shrunk or stretched. If the value is shrink, the row or column can only be resized smaller. If
expand, it can only be resized larger. If none, the row or column is frozen at its requested size.
# Let the 1st column get smaller, but not bigger
table configure . c0 -resize shrink
# Let the 2nd column get bigger, not smaller
table configure . c1 -resize expand
# Don't resize the first row
table configure . r0 -resize none
The following example packs a canvas, two scrollbars, and a title. The rows and columns containing the scroll-
bars are frozen at their requested size, so that even if the frame is resized, the scrollbars will remain the
same width.
table . \
.title 0,0 -cspan 3 \
.canvas 1,1 -fill both \
.vscroll 1,2 -fill y \
.hscroll 2,1 -fill x
# Don't let the scrollbars resize
table configure . c2 r2 -resize none
# Create an empty space to balance the scrollbar
table configure . c0 -width .vscroll
Note that the value of the -width option is the name of a widget window. This indicates that the width of the
column should be the same as the requested width of .vscroll.
Finally, the forget operation removes widgets from the table.
# Remove the windows from the table
table forget .quit .frame
It's not necessary to specify the container. The table command determines the container from the widget name.
OPERATIONS
The following operations are available for the table:
table container ?widget index option value?...
Adds the widget widget to the table at index. Index is a row,column position in the table. It must be in
the form row,column where row and column are the respective row and column numbers, starting from zero
(0,0 is the upper leftmost position). Row and column may also be numeric expressions that are recursively
evaluated. If a table doesn't exist for container, one is created. Widget is the path name of the win-
dow, that must already exist, to be arranged inside of container. Option and value are described in the
WIDGET OPTIONS section.
table arrange container
Forces the table to compute its layout immediately. Normally, the table geometry manager will wait until
the next idle point, before calculating the size of its rows and columns. This is useful for collecting
the normal sizes of rows and columns, that are based upon the requested widget sizes.
table cget container ?item? option
Returns the current value of the configuration option specific to item given by option. Item is either a
row or column index, or the path name of a widget. Item can be in any form describe in the configure
operation below. If no item argument is provided, then the configuration option is for the table itself.
Option may be any one of the options described in the appropiate section for item.
table configure container item... ?option value?...
Queries or modifies the configuration options specific to item. If no option is specified, this command
returns a list describing all of the available options for item If the argument item is omitted, then the
specified configuration options are for the table itself. Otherwise item must be either a row or column
specification, or the path name of a widget. The following item types are available.
Ci Specifies the column of container to be configured. Item must be in the form Cn, where i is the
index of the column. See the COLUMN OPTIONS section.
Ri Specifies the row of container to be configured. Item must be in the form Ri, where i is the index
of the row. See the ROW OPTIONS section.
widget Specifies a widget of container to be queried. Widget is the path name of a widget packed in con-
tainer. See the WIDGET OPTIONS section.
No argument
Specifies that the table itself is to be queried. See the TABLE OPTIONS section for a description
of the option-value pairs for the table.
The option and value pairs are specific to item. If option is specified with no value, then the command
returns a list describing the one named option (this list will be identical to the corresponding sublist
of the value returned if no option is specified). If one or more option-value pairs are specified, then
the command modifies the given option(s) to have the given value(s); in this case the command returns the
empty string.
table extents container index
Queries the location and dimensions of row and columns in the table. Index can be either a row or column
index or a table index. Returns a list of the x,y coordinates (upperleft corner) and dimensions (width
and height) of the cell, row, or column.
table forget widget ?widget?...
Requests that widget no longer have its geometry managed. Widget is the pathname of the window currently
managed by some table. The window will be unmapped so that it no longer appears on the screen. If widget
is not currently managed by any table, an error message is returned, otherwise the empty string.
table info container item
Returns a list of the current configuration options for item. The list returned is exactly in the form
that might be specified to the table command. It can be used to save and reset table configurations. Item
must be one of the following.
Ci Specifies the column of container to be queried. Item must be in the form Cn, where n is the
index of the column.
Ri Specifies the row of container to be queried. Item must be in the form Ri, where i is the index of
the row.
widget Specifies a widget of container to be queried. Widget is the path name of a widget packed in con-
tainer.
No argument
Specifies that the table itself is to be queried.
table locate container x y
Returns the table index (row,column) of the cell containing the given screen coordinates. The x and y
arguments represent the x and y coordinates of the sample point to be tested.
table containers ?switch arg?
Returns a list of all container windows matching a given criteria (using switch and arg). If no switch
and arg arguments are given, the names of all container windows (only those using the table command) are
returned. The following are valid switches:
-pattern pattern
Returns a list of pathnames of all container windows matching pattern.
-slave window
Returns the name of the container window of table managing window. Window must be the path name of
widget. If window is not managed by any table, the empty string is returned.
table search container ?switch arg?...
Returns the names of all the widgets in container matching the criteria given by switch and arg. Con-
tainer is name of the container window associated with the table to be searched. The name of the widget
is returned if any one switch-arg criteria matches. If no switch-arg arguments are given, the names of all
widgets managed by container are returned. The following are switches are available:
-pattern pattern
Returns the names of any names of the widgets matching pattern.
-span index
Returns the names of widgets that span index. A widget does not need to start at index to be
included. Index must be in the form row,column, where row and column are valid row and column num-
bers.
-start index
Returns the names of widgets that start at index. Index must be in the form row,column, where row
and column are valid row and column numbers.
TABLE OPTIONS
To configure the table itself, you omit the item argument when invoking the configure operation.
table configure container ?option value?...
The following options are available for the table:
-padx pad
Sets how much padding to add to the left and right exteriors of the table. Pad can be a list of
one or two numbers. If pad has two elements, the left side of the table is padded by the first
value and the right side by the second value. If pad has just one value, both the left and right
sides are padded evenly by the value. The default is 0.
-pady pad
Sets how much padding to add to the top and bottom exteriors of the table. Pad can be a list of
one or two numbers. If pad has two elements, the area above the table is padded by the first value
and the area below by the second value. If pad is just one number, both the top and bottom areas
are padded by the value. The default is 0.
-propagate boolean
Indicates if the table should override the requested width and height of the container window. If
boolean is false, container will not be resized. Container will be its requested size. The
default is 1.
WIDGET OPTIONS
widgets are configured by specifying the name of the widget when invoking the configure operation.
table configure container widget ?option value?...
Widget must be the path name of a window already packed in the table associated with container. The following
options are available for widgets:
-anchor anchor
Anchors widget to a particular edge of the cell(s) it resides. This option has effect only if the
space of the spans surrounding widget is larger than widget. Anchor specifies how widget will be
positioned in the space. For example, if anchor is center then the window is centered in the rows
and columns it spans; if anchor is w then the window will be aligned with the leftmost edge of the
span. The default is center.
-columnspan number
Sets the number of columns widget will span. The default is 1.
-columncontrol control
Specifies how the width of widget should control the width of the columns it spans. Control is
either normal, none, or full. The default is normal.
none The width of widget is not considered.
full Only the width of widget will be considered when computing the widths of the columns.
normal Indicates that the widest widget spanning the column will determine the width of the
span.
-fill fill
Specifies if widget should be stretched to fill any free space in the span surrounding widget. Fill
is either none, x, y, both. The default is none.
x The widget can grow horizontally.
y The widget can grow vertically.
both The widget can grow both vertically and horizontally.
none The widget does not grow along with the span.
-ipadx pixels
Sets how much horizontal padding to add internally on the left and right sides of widget. Pixels
must be a valid screen distance like 2 or 0.3i. The default is 0.
-ipady pixels
Sets how much vertical padding to add internally on the top and bottom of widget. Pixels must be a
valid screen distance like 2 or 0.3i. The default is 0.
-padx pad
Sets how much padding to add to the left and right exteriors of widget. Pad can be a list of one
or two numbers. If pad has two elements, the left side of widget is padded by the first value and
the right side by the second value. If pad has just one value, both the left and right sides are
padded evenly by the value. The default is 0.
-pady pad
Sets how much padding to add to the top and bottom exteriors of widget. Pad can be a list of one
or two numbers. If pad has two elements, the area above widget is padded by the first value and
the area below by the second value. If pad is just one number, both the top and bottom areas are
padded by the value. The default is 0.
-reqheight height
Specifies the limits of the requested height for widget. Height is a list of bounding values. See
the BOUNDING SIZES section for a description of this list. By default, the height of widget is its
requested height with its internal padding (see the -ipady option). The bounds specified by height
either override the height completely, or bound the height between two sizes. The default is "".
-reqwidth width
Specifies the limits of the requested width for widget. Width is a list of bounding values. See
the BOUNDING SIZES section for a description of this list. By default, the width of widget is its
requested width with its internal padding (set the -ipadx option). The bounds specified by width
either override the width completely, or bound the height between two sizes. The default is "".
-rowspan number
Sets the number of rows widget will span. The default is 1.
-rowcontrol control
Specifies how the height of widget should control the height of the rows it spans. Control is
either normal, none, or full. The default is normal.
none The height of widget is not considered.
full Only the height of widget will be considered when computing the heights of the rows.
normal Indicates that the tallest widget spanning the row will determine the height of the span.
COLUMN OPTIONS
To configure a column in the table, specify the column index as Ci, where i is the index of the column to be con-
figured.
table configure container Ci ?option value?...
If the index is specified as C*, then all columns of the table will be configured. The following options are
available for table columns.
-padx pad
Sets the padding to the left and right of the column. Pad can be a list of one or two numbers. If
pad has two elements, the left side of the column is padded by the first value and the right side
by the second value. If pad has just one value, both the left and right sides are padded evenly by
the value. The default is 0.
-resize mode
Indicates that the column can expand or shrink from its requested width when the table is resized.
Mode must be one of the following: none, expand, shrink, or both. If mode is expand the width of
the column is expanded if there is extra space in the container window. If mode is shrink its width
may be reduced beyond its requested width if there is not enough space in the container. The
default is none.
-width width
Specifies the limits within that the width of the column may expand or shrink. Width is a list of
bounding values. See the section BOUNDING SIZES for a description of this list. By default there
are no constraints.
ROW OPTIONS
To configure a row in the table, specify the row index as Ri, where i is the index of the row to be configured.
table configure container Ri ?option value?...
If the index is specified as R*, then all rows of the table will be configured. The following options are avail-
able for table rows.
-height height
Specifies the limits of the height that the row may expand or shrink to. Height is a list of
bounding values. See the section BOUNDING SIZES for a description of this list. By default there
are no constraints.
-pady pad
Sets the padding above and below the row. Pad can be a list of one or two numbers. If pad has two
elements, the area above the row is padded by the first value and the area below by the second
value. If pad is just one number, both the top and bottom areas are padded by the value. The
default is 0.
-resize mode
Indicates that the row can expand or shrink from its requested height when the table is resized.
Mode must be one of the following: none, expand, shrink, or both. If mode is expand the height of
the row is expanded if there is extra space in the container. If mode is shrink its height may be
reduced beyond its requested height if there is not enough space in the container. The default is
none.
BOUNDING SIZES
Sometimes it's more useful to limit resizes to an acceptable range, than to fix the size to a particular value or
disallow resizing altogether. Similar to the way the wm command lets you specify a minsize and maxsize for a
toplevel window, you can bound the sizes the container, a widget, row, or column may take. The -width, -height,
-reqwidth, and -reqheight options, take a list of one, two, or three values. We can take a previous example and
instead preventing resizing, bound the size of the scrollbars between two values.
table . \
.title 0,0 -cspan 3 \
.canvas 1,1 -fill both \
.vscroll 1,2 -fill y \
.hscroll 2,1 -fill x
# Bound the scrollbars between 1/8 and 1/2 inch
table configure . c2 -width { 0.125 0.5 }
table configure . r2 -height { 0.125 0.5 }
table configure . vscroll .hscroll -fill both
The scrollbars will get no smaller than 1/8 of an inch, or bigger than 1/2 inch. The initial size will be their
requested size, so long as it is within the specified bounds.
How the elements of the list are interpreted is dependent upon the number of elements in the list.
{} Empty list. No bounds are set. The default sizing is performed.
{ x } Fixes the size to x. The window or partition cannot grow or shrink.
{ min max }
Sets up minimum and maximum limits for the size of the window or partition. The window or par-
tition can be reduced less than min, nor can it be stretched beyond max.
{ min max nom }
Specifies minimum and maximum size limits, but also specifies a nominal size nom. This over-
rides the calculated size of the window or partition.
MISCELLANEOUS
Another feature is that you can put two widgets in the same cell of the table. This is useful when you want to
add decorations around a widget.
frame .frame -bd 1 -relief sunken
button .quit -text "Quit"
# Put both the frame and the button in the same cell.
table . \
.quit 1,0 -padx 2 -pady 2 \
.frame 1,0 -fill both
LIMITATIONS
A long standing bug in Tk (circa 1993), there is no way to detect if a window is already a container of a differ-
ent geometry manager. This is usually done by accident, such as the following where all three widgets are
arranged in the same container ".", but using different geometry managers.
table .f1
...
pack .f2
...
grid .f3
This leads to bizarre window resizing, as each geometry manager applies its own brand of layout policies. When
the container is a top level window (such as "."), your window manager may become locked as it responds to the
never-ending stream of resize requests.
KEYWORDS
frame, geometry manager, location, table, size