adjuster(3)
NAME
Tk::Adjuster - Allow size of packed widgets to be adjusted
by user
SYNOPSIS
use Tk::Adjuster; $adjuster = $widget->Adjuster(?options?);
WIDGET-SPECIFIC OPTIONS
- Name: restore
Class: Restore
Switch: -restore - Specifies a boolean value that determines whether the
Adjuster should forcibly attempt to make room for
itself (by reducing the size of its managed widget)
when it is unmapped (for example, due to a size change
in a top level window). The default value is 1. - Name: side
Class: Side
Switch: -side - Specifies the side on which the managed widget lies
relative to the Adjuster. In conjunction with the pack
geometry manager, this relates to the side of the mas
ter against which the managed widget and the Adjuster
are packed. Must be left, right, top, or bottom. Defaults to top. - Name: widget
Class: Widget
Switch: -widget - Specifies the widget which is to be managed by the
Adjuster.
DESCRIPTION
Tk::Adjuster is a Frame containing a "line" and a "blob".
Dragging with Mouse Button-1 results in a line being
dragged to indicate new size. Releasing Button-1 submits
GeometryRequests on behalf of the managed widget which
will cause the packer to change the widget's size.
If Drag is done with Shift button down, then GeometryRe
quests are made in "real time" so that text-flow effects
can be seen, but as a lot more work is done behaviour may
be sluggish.
If widget is packed with -side => left or -side => right
then width is adjusted. If packed -side => top or -side =>
bottom then height is adjusted.
packPropagate is turned off for the master window to pre
vent adjustment changing overall window size. Similarly
packPropagate is turned off for the managed widget if it
has things packed inside it. This is so that the Geome
tryRequests made by Tk::Adjuster are not overridden by
pack.
In addition, the managed widget is made non-expandable to
prevent the geometry manager reallocating freed space in
the master back to the managed widget. Note however that
expansion is turned off only after the Adjuster is mapped,
which allows the managed widget to expand naturally on
window creation.
The Tk::Widget method, packAdjust, calls pack on the wid
get, then creates an instance of Tk::Adjuster, and packs
that "after" the widget. Its use has two disadvantages
however: the Adjuster widget is not made available to the
caller, and options cannot be set on the Adjuster. For
these reasons, the Tk::Adjuster method, packAfter is pre
ferred, but packAdjust is retained for backwards compati
bility.
WIDGET METHODS
- $adjuster->packAfter(managed_widget, ?pack_options?)
- This command configures the Adjuster's -widget and
-side options respectively to managed_widget and the -side value specified in pack_options (top if not specified). It then packs the Adjuster after man_
aged_widget, with -fill set to x or y as appropriate. - $adjuster->packForget?(boolean)?
- This command calls Tk::Widget::packForget on the
Adjuster. If a parameter is provided and it has a
true boolean value, then packForget is also called on the managed widget. - $adjuster->slave
- This command returns the value $adjuster->cget('-wid_ get'), ie. the reference to the managed widget.
EXAMPLES
Using an Adjuster to separate two widgets, whereby the
left widget is managed, and right widget expands to fill
space on a window resize
- a) Using packAfter (preferred interface)
- use Tk;
use Tk::Adjuster; - my $f = MainWindow->new;
my $lst1 = $f->Listbox();
my $adj1 = $f->Adjuster();
my $lst2 = $f->Listbox(); - my $side = 'left';
$lst1->pack(-side => $side, -fill => 'both', -expand => - 1);
$adj1->packAfter($lst1, -side => $side);
$lst2->pack(-side => $side, -fill => 'both', -expand => - 1);
MainLoop; - b) Using packAdjust
use Tk;
use Tk::Adjuster;- my $f = MainWindow->new;
my $lst1 = $f->Listbox();
my $lst2 = $f->Listbox(); - my $side = 'left';
$lst1->packAdjust(-side => $side, -fill => 'both');
$lst2->pack (-side => $side, -fill => 'both', -ex - pand => 1);
MainLoop; - c) Using the standard Tk::Widget::pack
use Tk;
use Tk::Adjuster;- my $f = MainWindow->new;
my $side = 'left';
my $lst1 = $f->Listbox();
my $adj = $f->Adjuster(-widget => $lst1, -side => - $side);
my $lst2 = $f->Listbox(); - $lst1->pack(-side => $side, -fill => 'both', -expand =>
- 1);
$adj->pack (-side => $side, -fill => 'y');
$lst2->pack(-side => $side, -fill => 'both', -expand => - 1);
- MainLoop;
- Changing the above examples so that $side has the value
'right' means the left widget expands to fill space on a
window resize. - Changing the above examples so that $side has the value
'top' produces a testcase with a horizontal Adjuster.
Here the bottom widget expands to fill space on a window
resize. Packing to the 'bottom' makes the top widget
expand to fill space on window resize. - Using -restore => 0 for multiple columns
- In the case of multiple columns (or rows) the "restore"
functionality of the Adjuster can be inconvenient. When
the user adjusts the width of one column and thereby
pushes the Adjuster of another column off the window, this
adjuster tries to restore itself by reducing the size of
its managed widget. This has the effect that column
widths shrink; and the original size is not restored when
the user reverses the originating change. The -restore option can be used to turn off this functionality. (It
makes some sense, however, to leave -restore turned on for the first-packed Adjuster, so that at least one Adjuster
always remains visible.)
use Tk;
use Tk::Adjuster;
my $f = MainWindow->new;
my $lst1 = $f->Listbox();
my $adj1 = $f->Adjuster();
my $lst2 = $f->Listbox();
my $adj2 = $f->Adjuster(-restore => 0);
my $lst3 = $f->Listbox();- my $side = 'left';
$lst1->pack(-side => $side, -fill => 'both', -expand => - 1);
$adj1->packAfter($lst1, -side => $side);
$lst2->pack(-side => $side, -fill => 'both', -expand => - 1);
$adj2->packAfter($lst2, -side => $side);
$lst3->pack(-side => $side, -fill => 'both', -expand => - 1);
- MainLoop;
BUGS
It is currently not possible to configure the appearance
of the Adjuster. It would be nice to be able to set the
width and relief of the Adjuster "line" and the pres
ence/absence of the "blob" on the Adjuster.
- Tk::Adjuster works theoretically with the grid geometry
manager but there are currently some problems which seem
to be due to bugs in grid: - a) There's never an Unmap event for the adjuster, so the
- "restore"
functionality has no effect.
- b) After adjusting, widgets protrude into the border of
- the master.
c) grid('Propagate', 0) on MainWindow has no effect - window shrinks/grows
when widgets are adjusted.
- d) Widgets shuffle to correct position on startup