place(3p)

NAME
Tk::place - Geometry manager for fixed or rubber-sheet placement

SYNOPSIS
$widget->place?(-option=>value?, -option=>value, ...)?

$widget->placeForget

$widget->placeInfo

$master->placeSlaves

DESCRIPTION
The placer is a geometry manager for Tk. It provides simple fixed placement of windows, where you specify the exact size and location of one window, called the slave, within another window, called the $master. The placer also provides rubber-sheet placement, where you specify the size and location of the slave in terms of the dimensions of the master, so that the slave changes size and location in response to changes in the size of the master. Lastly, the placer allows you to mix these styles of placement so that, for example, the slave has a fixed width and height but is centered inside the master.

$slave->place?(-option=>value?, -option=>value, ...?)?
    The place method arranges for the placer to manage the geometry of $slave. The remaining arguments consist of one or more -option=>value pairs that specify the way in which $slave's geometry is managed. If the placer is already managing $slave, then the -option=>value pairs modify the configuration for $slave. The place method returns an empty string as result. The following -option=>value pairs are supported:

    -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
        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
        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. 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
        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
        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. 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
        Where 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
        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
        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
        Size specifies the height for $slave in screen units (i.e. any of the forms accepted by Tk_GetPixels). The height will be the outer dimension of $slave including its border, if any. If 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
        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
        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, 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.

$slave->placeSlaves
    The placeSlaves method returns a list of all the slave windows for which $master is the master. If there are no slaves for $master then an empty list is returned.

$slave->placeForget
    The placeForget method causes the placer to stop managing the geometry of $slave. As a side effect of this method call $slave will be unmapped so that it doesn't appear on the screen. If $slave isn't currently managed by the placer then the method call has no effect. placeForget returns an empty string as result.

$slave->placeInfo
    The placeInfo method returns a list giving the current configuration of $slave. The list consists of -option=>value pairs in exactly the same form as might be specified to the place method. If the configuration of a window has been retrieved with placeInfo, that configuration can be restored later by first using placeForget to erase any existing information for the window and then invoking place with the saved information.

FINE POINTS
It is not necessary for the master window to be the parent of the slave window. This feature is useful in at least two situations. First, for complex window layouts it means you can create a hierarchy of subwindows whose only purpose is to assist in the layout of the parent. The ``real children'' of the parent (i.e. the windows that are significant for the application's user interface) can be children of the parent yet be placed inside the windows of the geometry-management hierarchy. This means that the path names of the ``real children'' don't reflect the geometry-management hierarchy and users can specify options for the real children without being aware of the structure of the geometry-management hierarchy.

A second reason for having a master different than the slave's parent is to tie two siblings together. For example, the placer can be used to force a window always to be positioned centered just below one of its siblings by specifying the configuration

-in=>$sibling, -relx=>0.5, -rely=>1.0, -anchor=>'n', -bordermode=>'outside'

Whenever the $sibling widget is repositioned in the future, the slave will be repositioned as well.

Unlike many other geometry managers (such as the packer) the placer does not make any attempt to manipulate the geometry of the master windows or the parents of slave windows (i.e. it doesn't set their requested sizes). To control the sizes of these windows, make them windows like frames and canvases that provide configuration options for this purpose.

SEE ALSO
Tk::form Tk::grid Tk::pack

KEYWORDS
geometry manager, height, location, master, place, rubber sheet, slave, width