21.2. Geometry Managers
Creating widgets and determining how
to display them are done with separate commands. You can create a
widget with one of the widget creation methods (such as
Button, Canvas, etc.), but you
display them using a geometry manager. The three geometry managers
are pack, grid,
place, and form.
pack is by far the most commonly used.
You can either pack a widget as you create it or create the widget
object and pack it separately. For example, the previous
"Hello World" example might have
read:
#!/usr/bin/perl -w
use Tk;
my $mw = MainWindow->new;
$button = $mw->Button(-text => "Hello World!", -command =>sub{exit});
$button->pack;
MainLoop;
21.2.1. The pack Geometry Manager
With the
pack geometry manager, widgets cannot overlap or
cover each other, either partially or completely. Once a widget is
packed into a window, the next widget is packed in the remaining
space around it. pack sets up an
"allocation rectangle" for each
widget, determined by the dimensions of the parent window and the
positioning of the widgets already packed into it. This means that
the order in which you pack your widgets is very important.
By default, pack places widgets at the top center
of the allocation rectangle. However, you can use options to
pack to control where a widget is placed and how
much padding is placed around it. Options for pack
are:
- -side => side
-
Puts the widget against the specified
side of the window. Values for side are
left, right,
top, and bottom. The default is
top.
- -fill => direction
-
Causes the widget to fill the
allocation rectangle in the specified direction. Values for
direction are none,
x, y, and
both. The default is none.
- -expand => boolean
-
Causes the allocation rectangle to fill
the remaining space available in the window. Values are
yes, no, 1,
and 0. The default is 0
(no).
- -anchor => position
-
Anchors the widget inside the
allocation rectangle. Values for positionare n, ne,
e, se, s,
sw, w, nw,
and center. The default is
center.
- -after => $widget
-
Puts the widget after another widget in
packing order.
- -before => $widget
-
Puts the widget before another widget
in packing order.
- -in => $window
-
Packs the widget inside another window
rather than inside its parent.
- -ipadx => amount
-
Increases the size of the widget
horizontally by amount x 2.
amount can be represented as a number
followed by c (centimeters), i
(inches), m (millimeters), and
p (printer points). Pixels are the default units.
- -ipady => amount
-
Increases the size of the widget vertically by
amount x 2.
amount can be represented as a number followed by
c (centimeters), i (inches),
m (millimeters), and p (printer
points). Pixels are the default units.
- -padx => amount
-
Places padding on the left and right
of the widget. amount can be represented
as a number followed by c (centimeters),
i (inches), m (millimeters),
and p (printer points). Pixels are the default
units.
- -pady amount
-
Places padding on the top and bottom of the widget.
amount can be represented as a number
followed by c (centimeters), i
(inches), m (millimeters), and
p (printer points). Pixels are the default units.
21.2.1.1. pack methods
The following methods are associated with widgets managed with
pack:
- packForget
-
Causes a widget to be removed from
view:
$widget->packForget;
The widget is not destroyed, but it is no longer managed by
pack. The widget is removed from the packing
order, so if it was repacked later, it would appear at the end of the
packing order.
- packInfo
-
Returns a list containing all pack
information about that widget:
$info = $widget->packInfo;
- packPropagate
-
Enables or suppresses automatic
resizing of a Toplevel or Frame widget to accommodate items packed
inside of it. Automatic resizing is on by default; the following line
turns off automatic resizing:
$widget->packPropagate(0);
- packSlaves
-
Returns an ordered list of all the
widgets packed into the parent widget:
$children = $widget->packSlaves;
21.2.2. The grid Geometry Manager
The
grid geometry manager divides the window into a
grid composed of columns and rows starting at 0,0 in the upper
lefthand corner. The resulting grid resembles a spreadsheet, with
each widget assigned a cell according to the options to
grid. To create a grid, create a frame packed
inside the parent window and then grid the widgets within the frame.
You can specify explicit rows and columns using options to
grid. However, if several widgets are meant to
appear in the same row, you can use a single grid
command with a list of widgets rather than calling
grid for each one. The first widget invokes the
grid command, and all other widgets for that
column are specified as options to grid. Any
subsequent grid commands increment the row by one
and start again.
You can use special characters as placeholders:
- - (minus sign)
-
The previous widget should span
this column as well. May not follow ^ or
x.
- x
-
Leaves a blank space.
- ^
-
The widget above this one (same
column, previous row) should span this row.
Options to grid are:
- -column => n
-
The
column in which to place the widget. n is
any integer >= 0.
- -row => m
-
The row in which to place
the widget. m is any integer >= 0.
- -columnspan => n
-
The
number of columns for the widget to span, beginning with the column
specified with -column.
n is any integer > 0.
- -rowspan => m
-
The
number of rows for the widget to span, beginning with the row
specified with -row. mis any integer > 0.
- -sticky => sides
-
Sticks widget to specified
side(s). sides contains characters
n, s, e, or
w.
- -in => $window
-
Grids widget inside another window
instead of its parent.
- -ipadx => amount
-
Increases the size of the widget
horizontally by amount x 2.
amount can be represented as a number
followed by c (centimeters), i
(inches), m (millimeters), and
p (printer points). Pixels are the default units.
- -ipady => amount
-
Increases the size of the widget vertically by
amount x 2.
amount can be represented as a number
followed by c (centimeters), i
(inches), m (millimeters), and
p (printer points). Pixels are the default units.
- -padx => amount
-
Places padding on the left and right
of the widget. amount can be represented
as a number followed by c (centimeters),
i (inches), m (millimeters),
and p (printer points). Pixels are the default
units.
- -pady amount
-
Places padding on the top and bottom of the widget.
amount can be represented as a number
followed by c (centimeters), i
(inches), m (millimeters), and
p (printer points). Pixels are the default units.
21.2.2.1. grid methods
The following methods are associated with widgets managed by
grid:
- gridColumnconfigure
-
Configures the column specified by the
first argument using -weight and
-minsize arguments. The -weight
argument determines the amount of space to allocate to that column,
and the -minsize argument sets the minimum size in
pixels. For example:
$widget->gridColumnconfigure(3, -weight => 1);
- gridRowconfigure
-
Configures the row specified by the
first argument using -weight and
-minsize arguments. The -weight
argument determines the amount of space to allocate to that row, and
the -minsize argument sets the minimum size in
pixels. For example:
$widget->gridRowconfigure(3, -weight => 1);
- gridRemove
-
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.
gridRemove remembers the previous configuration
options for the window. So, if $slave is managed
once more by the grid geometry manager, the
previous values will be retained.
- gridBbox
-
Returns the
bounding box in pixels for the space occupied by the specified grid
position (in the order of column, row). For example:
$widget->gridBbox(3,2);
- gridForget
-
Causes the
widget(s) to be removed from view. Additional widgets can be
specified as arguments.
$widget1->gridForget($widget2, widget3, ...);
- gridInfo
-
Returns
information about the widget in list format:
$widget->gridInfo;
- gridLocation
-
Returns
the column and row of the widget nearest the specified x,y
coordinates (in pixels):
$widget->gridLocation(120, 32);
- gridPropagate
-
Turns
off automatic resizing of the widget:
$widget->gridPropagate;
- gridSize
-
Returns the
size of the grid, i.e., the number of columns and rows:
$widget->gridSize;
- gridSlaves
-
Returns a
list of all widgets contained within a master widget. Optional
-row and -column arguments
restrict the response to the widget(s) within that row or column:
@children = $widget->gridSlaves(-row => 2);
21.2.3. The place Geometry Manager
The
place geometry manager lets you position a window
at explicit x,y coordinates. With place, you can
overlap widgets, which isn't allowed with
grid or pack. For example, to
position a button widget at the upper-left corner of a window:
$button->place(-x => 0, -y => 0);
Options to place are:
- -anchor => position
-
The position in the widget that will
be placed at the coordinates specified. Values for
position are n,
ne, e, se,
s, sw, w,
nw, and center. Default is
nw.
- -bordermode => location
-
Determines whether the border portion
of the widget is included in the coordinate system. Values for
location are inside,
outside, and ignore.
- -height => amount
-
Absolute height of the widget.
amount can be represented as a number
followed by c (centimeters), i
(inches), m (millimeters), and
p (printer points). Pixels are the default units.
- -in => $window
-
The child widget will be packed inside
the specified window instead of the parent that created it. Any
relative coordinates or sizes will still refer to the parent.
- -relheight => ratio
-
The height of the widget relates to the
parent widget's height by the specified ratio.
- -relwidth => ratio
-
The width of the widget relates to the parent
widget's width by the specified ratio.
- -relx => xratio
-
The widget will be placed relative to
its parent by the specified ratio. xratiois a floating point number from 0.0 to 1.0, with 0.0 representing the
left side of the parent widget and 1.0 representing the right side.
- -rely => yratio
-
The widget will be placed relative to its parent by the specified
ratio. yratio is a floating point number
from 0.0 to 1.0, with 0.0 representing the top of the parent widget
and 1.0 representing the bottom.
- -width => amount
-
The width of the widget will be the
specified amount. amount can be
represented as a number followed by c
(centimeters), i (inches), m
(millimeters), and p (printer points). Pixels are
the default units.
- -x => xcoord
-
The widget will
be placed at the specified x coordinate.
- -y => ycoord
-
The widget will
be placed at the specified y coordinate.
The following methods are associated with widgets managed by
place:
- placeForget
-
Causes the widget to be removed from
view.
- placeInfo
-
Returns information about the widget.
- placeSlaves
-
Returns a list of widgets managed by
the specified parent widget.
21.2.4. The form Geometry Manager
The form geometry
manager arranges the geometry of children in the parent window
according to attachment rules. In addition, form
can be used as a replacement for the existing Tk
pack and place geometry
managers. For example, to position a widget $top_w
on top of $bot_w, you'd do this:
$bot_w->form(-top=>[$topw_w, 0]);
Options to form are:
- -b => attachment
-
Abbreviation for the
-bottom option.
- -bottom => attachment
-
Specifies an attachment for the bottom
edge of the slave window.
- -bottomspring => attachment
-
Specifies the weight of the spring at
the bottom edge of the slave window.
- -bp => value
-
Abbrevation for the
-padbottom option.
- -bs => weight
-
Abbrevation for the
-bottomspring option.
- -fill => style
-
Specifies the fillings when springs
are used for this widget. The value must be x,
y, both, or
none.
- -in => $master
-
Places the slave window into the
specified $master window. If the slave was
originally in $another_master, all attachment
values with respect to $original_master are
discarded. The attachment values will need to be specified again. If
you use -in, it must be used first in the options
list.
- -l => attachment
-
Abbreviation for the
-left option.
- -left => attachment
-
Specifies an attachment for the left
edge of slave window, $slave.
- -leftspring => weight
-
Specifies the weight of the spring at
the edge of the slave window, $slave.
- -lp => value
-
Abbreviation for the
-padleft option.
- -ls => weight
-
Abbreviation for the
-leftspring option.
- -padbottom => value
-
Specifies the amount of external
padding to leave on the bottom side of the slave.
- -padleft => value
-
Specifies the amount of external
padding to leave on the left side of the slave.
- -padright => value
-
Specifies the amount of external
padding to leave on the right side of the slave.
- -padtop => value
-
Specifies the amount of external
padding to leave on the top side of the slave.
- -padx => value
-
Specifies the amount of external
padding to leave on both the left and right sides of the slave.
- -pady => value
-
Specifies the amount of external
padding to leave on both the top and bottom sides of the slave.
- -r => attachment
-
Abbreviation for the
-right option.
- -right => attachment
-
Specifies an attachment for the right
edge of the slave window.
- -rightspring => weight
-
Specifies the weight of the spring at
the right edge of the slave window.
- -rp => value
-
Abbreviation for the
-padright option.
- -rs => weight
-
Abbreviation for the
-rightspring option.
- -t => attachment
-
Abbreviation for the
-top option.
- -top => attachment
-
Specifies an attachment for the top edge
of the slave window.
- -topspring => weight
-
Specifies the weight of the
spring at the top edge of the slave window.
- -tp => value
-
Abbreviation for the
-padtop option.
- -ts => weight
-
Abbreviation for the
-topspring option.
The following methods are associated with widgets managed by
form:
- formCheck
-
Checks whether this is a circular
dependancy between the master's slaves. It returns
true if the dependancy exists and false otherwise.
- formForget
-
Removes the slave from its master and
unmaps its window. The slave will no longer be managed by
form. All attachment values with respect to
$master are discarded.
- formGrid($size_x, $size_y)
-
Returns the number of grids to
$master as integers in the form
$size_x, $size_y. You may
change the number of grids on the master window by passing
$size_x and $size_y to
formGrid.
- formInfo(-option)
-
Queries the attachment options of a
slave window. -option can be any of the options
accepted by form. With no options,
formInfo returns the current configuration values.
- formSlaves
-
Returns a list of all the slaves for
the master window.
 |  |  |
| 21. Perl/Tk |  | 21.3. Common Widget Configuration Options |
Copyright © 2002 O'Reilly & Associates. All rights reserved.