=head1 Win32::GUI Tutorial - Part 2 - Adding functionality

=head2 Some more control types

In part 1 of this tutorial, we covered the basics of Win32::GUI programming,
using a simple label control to display information. But real-world
applications don't just display information as labels. We need to be able to
obtain information from the user, respond to mouse clicks, etc etc.

Some of the basic Windows controls supported by Win32::GUI include

=over 4

=item *

Buttons, for taking actions.

=item *

Edit boxes, for data entry.

=item *

Checkboxes, for selecting options from a list.

=item *

Radio buttons, for choosing from mutually exclusive options.

=item *

Combo boxes and list boxes, for selection from lists.

=item *

And many other more complex controls, such as list views, tree views, status
bars, tab strips, etc.

=back

We have already covered nearly all of the programming techniques for using
these controls in our discussion of the label control in part 1. The following
section summarises the basic controls available, and any important issues
regarding their use. Armed with this and the main Win32::GUI documentation, it
should be possible to develop reasonably complex applications.

=head2 Summary of the Available Controls

For this part of the tutorial, we will use a very basic "framework"
application, to which we can add functionality. We won't worry about issues
like positioning, layout, resizing, etc, as these will only distract from the
main point, which is the control handling.

So, our basic application is

    use Win32::GUI;

    $main = Win32::GUI::Window->new(-name => 'Main', -text => 'Perl',
				    -width => 200, -height => 200);

    $main->Show();
    Win32::GUI::Dialog();

    sub Main_Terminate {
	-1;
    }

Now, the basic approach to adding any control to a window is the same. We saw
it before, when we added a label. We simply use the window's AddXXX() method,
where C<XXX> is the control type we want to add. So, we have, AddButton(),
AddTextfield(), AddCheckbox(), AddCombobox(), AddListbox(), AddRadioButton(),
etc.

All of these methods work the same way, in that they take a series of options,
which define the appearance and behaviour of the control. Many of the options
are common to all Win32::GUI controls (such as C<-width> and C<-height>) but a
few are control-specific.

The controls themselves support events, much like the main window with its
C<Terminate> event. Events are control-specific, but tend to be fairly general
(many controls have a C<Click> event, which occurs when the user clicks the
mouse on the control, for example).

=head2 Some control-specific issues

=over 4

=item Labels

None. We saw labels in some detail in the last part of this tutorial. Most of
what we learnt applies equally to all other controls.

=item Buttons

None. To make a button do something, add a handler for the C<Click> event.

=item Check Boxes

To get or set the "checked" state, use the Checked() method. There are three
states - unchecked (0), checked (1) and indeterminate or grayed (2). Use the
C<Click> event to respond to changes in state.

=item Text Fields

To get or set the contents of the text field, use the C<-text> option. The
C<-multiline> option allows entry of more than one line of text (but beware -
the C<-text> option contains a CRLF sequence ("\r\n") at the end of each line,
not just LF ("\n") as is normal for Perl. See the documentation for the
C<-prompt> option to automatically add a label to a text field.

=item Progress Bars

A display-only control. Set the parameters with the SetRange() and SetStep()
methods, and update the display using the SetPos() or StepIt() methods.

=item List Boxes

By default, there are no items in the list. Fill the list box using the
AddString() method. Get the selected item using the SelectedItem() method.
Multiple-selection listboxes are created using the C<-multisel> option -- in
that case, use the SelectedItems() method to get a list of all the selected
items.

=item Combo Boxes

Similar to single-selection list boxes (although they display differently).

=item UpDown Controls

This is the little double-arrow control you often see attached to numeric text
fields in dialog boxes. Clicking the up arrow increases the value of the text
field, whereas clicking the down arrow decreases it.

The only significant complication with using an UpDown control is the need to
associate it with a text box. This is done using the Buddy() method, as

    $updown->Buddy($text)

Methods exist to set the range of values for the control, and to explicitly
set the value of the control. The control supports a C<Scroll> event, which is
fired when the control value changes (but not when the associated text box
changes!) The UpDown control's size is ignored, as it is attached to its buddy
when it is created.

=back

This covers the basic controls available in Win32::GUI. In part 3, we will
cover some of the subtleties of dialog boxes and main windows, and then in
part 4, we will be ready to cover some of the more complex user interface
options.
