=head1 NAME

Tk::Balloon - pop up help balloons.

=for pm Tixish/Balloon.pm

=for category Tix Extensions

=head1 SYNOPSIS

    use Tk::Balloon;
    ...
    $b = $top->Balloon(-statusbar => $status_bar_widget);

    # Normal Balloon:
    $b->attach($widget,
	       -balloonmsg => "Balloon help message",
	       -statusmsg => "Status bar message");

    # Balloon attached to entries in a menu widget:
    $b->attach($menu, -state => 'status',
		      -msg => ['first menu entry',
			       'second menu entry',
			       ...
			      ],
	      );

    # Balloon attached to individual items in a canvas widget:
    $b->attach($canvas, -balloonposition => 'mouse',
			-msg => {'item1' => 'msg1',
				 'tag2'  => 'msg2',
				  ...
				},
	      );

    # Balloon attached to items in a listbox widget:
    $b->attach($listbox, -balloonposition => 'mouse',
			 -msg => ['first listbox element',
				  '2nd listbox element',
				  ...
				 ],
	      );

=head1 DESCRIPTION

B<Balloon> provides the framework to create and attach help
balloons to various widgets so that when the mouse pauses over the
widget for more than a specified amount of time, a help balloon is
popped up.

=head2 Balloons and Menus or Listboxes

If the balloon is attached to a B<Menu> or B<Listbox> widget and the
message arguments are array references, then each element in the array
will be the message corresponding to a menu entry or listbox element.
The balloon message will then be shown for the entry which the mouse
pauses over. Otherwise it is assumed that the balloon is to be
attached to the B<Menu> or B<Listbox> as a whole. You can have
separate status and balloon messages just like normal balloons.

=head2 Balloons and Canvases

If the balloon is attached to a B<Canvas> widget and the message
arguments are hash references, then each hash key should correspond to
a canvas item ID or tag and the associated value will correspond to the
message for that canvas item. The balloon message will then be shown for
the current item (the one at the position of the mouse). Otherwise it is
assumed that the balloon is to be attached to the B<Canvas> as a whole.
You can have separate status and balloon messages just like normal
balloons.

=head2 Balloon Position

By default, the balloon pops up at the lower right side of the client.
If it would extend outside the lower screen border, its positioned at the
upper right side. If it would extend outside the right screen border
it's shown on the lower left side of the client. If it would extend
outside both the lower and the right screen border, it's positioned
at the upper left side of the client. Thus, the little arrow always
points to the attached client.

=head1 OPTIONS

B<Balloon> accepts all of the options that the B<Frame> widget
accepts. In addition, the following options are also recognized.

=over 4

=item B<-initwait>

Specifies the amount of time to wait without activity before
popping up a help balloon. Specified in milliseconds. Defaults to
350 milliseconds. This applies to both the popped up balloon and
the status bar message.

=item B<-state>

Can be one of B<'balloon'>, B<'status'>, B<'both'> or B<'none'>
indicating that the help balloon, status bar help, both or none
respectively should be activated when the mouse pauses over the
client widget. Default is B<'both'>.

=item B<-statusbar>

Specifies the widget used to display the status message. This
widget should accept the B<-text> option and is typically a
B<Label>. If the widget accepts the B<-textvariable> option and
that option is defined then it is used instead of the B<-text>
option.

=item B<-balloonposition>

Can be one of B<'widget'> or B<'mouse'>. It controls where the balloon
will popup. B<'widget'> makes the balloon appear at the lower right
corner of the widget it is attached to (default), and B<'mouse'> makes
the balloon appear below and to the right of the current mouse position.

=item B<-postcommand>

This option takes a B<CODE> reference which will be executed before the
balloon and statusbar messages are displayed and should return a true
or false value to indicate whether you want the balloon to be displayed
or not. This also lets you control where the balloon is positioned by
returning a true value that looks like I<X,Y> (matches this regular
expression: C</^(\d+),(\d+)$/>). If the postcommand returns a value that
matches that re then those coordinates will be used as the position to
post the balloon. I<Warning:> this subroutine should return quickly or
the balloon response will appear slow.

=item B<-cancelcommand>

This option takes a B<CODE> reference which will be executed before the
balloon and statusbar messages are canceled and should return a true
or false value to indicate whether you want the balloon to be canceled
or not. I<Warning:> this subroutine should return quickly or the balloon
response will appear slow.

=item B<-motioncommand>

This option takes a B<CODE> reference which will be executed for any
motion event and should return a true or false value to indicate
whether the currently displayed balloon should be canceled (deactivated).
If it returns true then the balloon will definitely be canceled, if it
returns false then it may still be canceled depending the internal rules.
I<Note:> a new balloon may be posted after the B<-initwait> time
interval, use the B<-postcommand> option to control that behavior.
I<Warning:> the subroutine should be extremely fast or the balloon
response will appear slow and consume a lot of CPU time (it is executed
every time the mouse moves over the widgets the balloon is attached to).

=item B<-numscreens>

This option accepts an integer 1 or greater. This option should be used
to avoid disjointed balloons across multiple screens in single logical
sceen (SLS) mode. This only currently works in the horizontal direction.
Example: If you are running dual screens in SLS mode then you would set
this value to 2. Default value is 1.

=back

=head1 METHODS

The B<Balloon> widget supports only three non-standard methods:

=head2 B<attach(>I<widget>, I<options>B<)>

Attaches the widget indicated by I<widget> to the help system. The
allowed options are:

=over 4

=item B<-statusmsg>

The argument is the message to be shown on the status bar when the
mouse pauses over this client. If this is not specified, but
B<-msg> is specified then the message displayed on the status bar
is the same as the argument for B<-msg>. If you give it a scalar
reference then it is dereferenced before being displayed. Useful
if the postcommand is used to change the message.

=item B<-balloonmsg>

The argument is the message to be displayed in the balloon that
will be popped up when the mouse pauses over this client. As with
B<-statusmsg> if this is not specified, then it takes its value
from the B<-msg> specification if any. If neither B<-balloonmsg>
nor B<-msg> are specified, or they are the empty string then
no balloon is popped up instead of an empty balloon. If you
give it a scalar reference then it is dereferenced before being
displayed. Useful if the postcommand is used to change the message.

=item B<-msg>

The catch-all for B<-statusmsg> and B<-balloonmsg>. This is a
convenient way of specifying the same message to be displayed in
both the balloon and the status bar for the client.

=item B<-initwait>

=item B<-state>

=item B<-statusbar>

=item B<-balloonposition>

=item B<-postcommand>

=item B<-cancelcommand>

=item B<-motioncommand>

These options allow you to override the balloon's default value for
those option for some of the widgets it is attached to. It accepts the
same values as above and will default to the B<Balloon>'s value.

=back

=head2 B<detach(>I<widget>B<)>

Detaches the specified I<widget> from the help system.

=head2 B<destroy>

Destroys the specified balloon.

=head1 ADVERTISED SUBWIDGETS

The balloon label is advertised as C<message>.

=head1 EXAMPLES

See the balloon demo included with the widget demo script that came with
the distribution for examples on various ways to use balloons.

=head1 NOTES

Because of the overhead associated with each balloon you create (from
tracking the mouse movement to know when to activate and deactivate
them) you will see the best performance (low CPU consumption) if you
create as few balloons as possible and attach them to as many widgets
as you can.  In other words, don't create a balloon for each widget
you want to attach one to.

=head1 CAVEATS

Pressing any button will deactivate (cancel) the current balloon,
if one exists. You can usually make the balloon reappear by moving
the mouse a little. Creative use of the 3 command options can help
you out also. If the mouse is over the balloon when a menu is unposted
then the balloon will remain until you move off of it.

=head1 BUGS

If using balloons attached to listbox entries or canvas items in a
scrolled widget, then the subwidget have to be used:

    $balloon->attach($w->Subwidget("scrolled"), -msg => ...);

=head1 AUTHORS

B<Rajappa Iyer> rsi@earthling.net did the original coding.

B<Jason A. Smith> <smithj4@rpi.edu> added support for menus and made some
other enhancements.

B<Slaven Rezic> <eserte@cs.tu-berlin.de> added support for canvas items.

B<Gerhard Petrowitsch> <gerhard@petrowitsch.de> added intelligent positioning

B<Jack Dunnigan> <dunniganj@cpan.org> Made positioning I<more> intelligent and
added support for multiple monitors under single logical screen.

=head1 HISTORY

The code and documentation was derived from Balloon.tcl from the
Tix4.0 distribution by Ioi Lam and modified by the above mentioned
authors. This code may be redistributed under the same terms as Perl.

=cut