Win32::GUI Tutorial - Part 2 - Adding functionality

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

• Buttons, for taking actions.

• Edit boxes, for data entry.

• Checkboxes, for selecting options from a list.

• Radio buttons, for choosing from mutually exclusive options.

• Combo boxes and list boxes, for selection from lists.

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

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.

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 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 -width and -height) but a few are control-specific.

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

Some control-specific issues

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.

Buttons

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

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 Click event to respond to changes in state.

Text Fields

To get or set the contents of the text field, use the -text option. The -multiline option allows entry of more than one line of text (but beware - the -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 -prompt option to automatically add a label to a text field.

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.

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 -multisel option -- in that case, use the SelectedItems() method to get a list of all the selected items.

Combo Boxes

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

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 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.

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.