Place

The place method allows one to place at some fixed location a widget within a window. The basic usage is

$widget->place( [ option => value ] );

For the use of place, one must specify the x and y coordinates of where in the window the widget is to be positioned; a window's coordinates start at (x, y) = (0, 0) in the upper left hand corner, with x increasing to the right and y increasing downwards.

Our basic previous example rewritten to use place is as follows.

#!perl
# file place1.pl
use Tk;
use strict;
my $mw = MainWindow->new;
$mw->title('Place Example');
my $title = $mw->Label(-text => "Example of using place \non several widgets");
my $cb1 = $mw->Checkbutton(-text => 'Checkbutton 1');
my $button = $mw->Button(-text => 'A Button');
my $label = $mw->Label(-text => 'A Label');
my $cb2 = $mw->Checkbutton(-text => 'Checkbutton 2');
my $exit = $mw->Button(-text => 'Exit',
                       -command => [$mw => 'destroy']);
$title->place(-x => 30, -y => 10);
$cb1->place(-x => 1, -y => 50);
$cb2->place(-x => 100, -y => 50);
$label->place(-x => 70, -y => 90);
$exit->place(-x => 70, -y => 120);
MainLoop;

which results in the following window:

Figure 2.9: An example of the use of place

As discussed in the Tk documentation, available options to place are as follows.

• -in => $master
  $master is the reference to the window relative to which $slave is to be placed. $master must either be $slave's parent or a descendant of $slave's parent. In addition, $master and $slave must both be descendants of the same top-level window. These restrictions are necessary to guarantee that $slave is visible whenever $master is visible. If this option isn't specified then the master defaults to $slave's parent.
• -x => location
  The location specifies the x-coordinate within the master window of the anchor point for $slave widget. The location is specified in screen units (i.e. any of the forms accepted by Tk_GetPixels) and need not lie within the bounds of the master window.
• -relx => location
  The location specifies the x-coordinate within the master window of the anchor point for $slave widget. In this case the location is specified in a relative fashion as a floating-point number: 0.0 corresponds to the left edge of the master and 1.0 corresponds to the right edge of the master. The location need not be in the range 0.0-1.0. If both -x and -relx are specified for a slave then their values are summed. For example, -relx=>0.5, -x=-2 positions the left edge of the slave 2 pixels to the left of the center of its master.
• -y => location
  The location specifies the y-coordinate within the master window of the anchor point for $slave widget. The location is specified in screen units (i.e. any of the forms accepted by Tk_GetPixels) and need not lie within the bounds of the master window.
• -rely => location
  The location specifies the y-coordinate within the master window of the anchor point for $slave widget. In this case the value is specified in a relative fashion as a floating-point number: 0.0 corresponds to the top edge of the master and 1.0 corresponds to the bottom edge of the master. The location need not be in the range 0.0-1.0. If both -y and -rely are specified for a slave then their values are summed. For example, -rely=>0.5, -x=>3 positions the top edge of the slave 3 pixels below the center of its master.
• -anchor => where
  This specifies which point of $slave is to be positioned at the (x, y) location selected by the -x, -y, -relx, and -rely options. The anchor point is in terms of the outer area of $slave, including its border, if any. Thus, if where is ``se'', then the lower-right corner of $slave's border will appear at the given (x, y) location in the master. The anchor position defaults to ``nw''.
• -width => size
  The size specifies the width for $slave in screen units (i.e. any of the forms accepted by Tk_GetPixels). The width will be the outer width of $slave, including its border, if any. If size is an empty string, or if no -width or -relwidth option is specified, then the width requested internally by the window will be used.
• -relwidth => size
  The size specifies the width for $slave. In this case the width is specified as a floating-point number relative to the width of the master: 0.5 means $slave will be half as wide as the master, 1.0 means $slave will have the same width as the master, and so on. If both -width and -relwidth are specified for a slave, their values are summed. For example, -relwidth=>1.0, -width=>5 makes the slave 5 pixels wider than the master.
• -height => size The size specifies the height for $slave in screen units, in any of the forms accepted by Tk_GetPixels. The height will be the outer dimension of $slave, including its border, if any. If the size is an empty string, or if no -height or -relheight option is specified, then the height requested internally by the window will be used.
• -relheight => size
  The size specifies the height for $slave. In this case the height is specified as a floating-point number relative to the height of the master: 0.5 means $slave will be half as high as the master, 1.0 means $slave will have the same height as the master, and so on. If both -height and -relheight are specified for a slave, their values are summed. For example, -relheight=>1.0, -height=>-2 makes the slave 2 pixels shorter than the master.
• -bordermode => mode
  The mode determines the degree to which borders within the master are used in determining the placement of the slave. The default and most common value is ``inside''. In this case the placer considers the area of the master to be the innermost area of the master, inside any border: an option of -x=>0 corresponds to an x-coordinate just inside the border and an option of -relwidth=>1.0 means $slave will fill the area inside the master's border. If mode is outside then the placer considers the area of the master to include its border; this mode is typically used when placing $slave outside its master, as with the options -x=>0, -y=>0, -anchor=>ne. Lastly, the mode may be specified as ``ignore'', in which case borders are ignored: the area of the master is considered to be its official X area, which includes any internal border but no external border. A bordermode of ``ignore'' is probably not very useful. If the same value is specified separately with two different options, such as -x and -relx, then the most recent option is used and the older one is ignored.