NAME

table - Arranges widgets in a table

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 widget 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 dynamically 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 confines 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 hierarchy. 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, listbox, 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 scrollbars 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 window, 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.

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.

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:

table search container ?switch arg?...

Returns the names of all the widgets in container matching the criteria given by switch and arg. Container 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:

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:

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:

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 configured.

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.

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 available for table rows.

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.

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 different 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