Button Widget Properties

In IDL, a button widget can be a button (push button), radio button, or checkbox.

A push button is activated by a single-click. Push buttons can be of any size. You can set the Menu attribute to yes for a button widget, and then it can contain a pull-down menu. When you do so, the Label is enclosed in a box to indicate that the button is a menu button.

Radio buttons have two states, set and unset, and they belong to a group that allows only one radio button selection for that group. The group is defined as all buttons contained in the same exclusive base widget. When a radio button in a base (in a group) is selected, any other button selection in that base is cleared. When you create a radio button in the IDL GUIBuilder, it is created in an exclusive base widget, and you can add only radio buttons to that base.

Checkboxes have two states, set and unset, and they are grouped in a non-exclusive base widget. The base widget allows for any number of checkboxes to be set at one time, and you can also use single checkboxes in your interface. When you create a checkbox in the IDL GUIBuilder, it is created in an non-exclusive widget base, and you can add only checkboxes to this base.

When programming in IDL, you create push buttons, radio buttons, and checkboxes using the WIDGET_BUTTON function. For more information, see WIDGET_BUTTON.

Creating Multiple Radio Buttons or Checkboxes

Click on the radio button or checkbox tool, and click on the location to add the button. This creates a base with one radio button or checkbox in it.

Click on the radio button or checkbox tool, and click in the radio button or checkbox base area you just created. This adds a radio button or checkbox to the base.

When you drop a button in an exclusive or non-exclusive base, the added buttons line up in columns; by default, these exclusive and non-exclusive bases have their Layout attribute set to Column.

Repeat step 2 until you have the desired number of buttons.

If you want to change the layout of the checkboxes or radio buttons, you can open the Properties dialog and set the Layout common attribute for the base widget to Row or Bulletin.

To set the properties for each button in the base, open the Properties dialog, click the push pin button to keep it on top, then click on each radio button or checkbox to set their individual properties.

Button, Radio Button, and Checkbox Widget Attributes

For button widgets, you can set common attributes and button-specific attributes. For a list of common attributes, see Common Attributes. The following is a list of button widget attributes, which apply to push buttons, radio buttons, and/or checkboxes:

Alignment

The Alignment attribute specifies how the text label is aligned in the button widget. These are the possible alignment values:

Alignment	Tab Mode
Bitmap	Tooltip
Label	Type
No Release

Center: The label text is centered.

Left: The label text is left-justified.

Right: The label text is right-justified.

In the generated *.pro file, this value is specified by the ALIGN_CENTER, the ALIGN_LEFT, or the ALIGN_RIGHT keyword to the widget creation routine.

Bitmap

The Bitmap attribute allows you to select a bitmap to be displayed in the push button, and it allows you to access the Bitmap Editor to create or modify a bitmap file (*.bmp file). This value applies only to buttons (not to radio buttons or checkboxes).

To set this value, set the Type value to Bitmap, then the Bitmap attribute displays in the Properties dialog. When the button type is "Bitmap", you can set the Bitmap attribute to the path and name of the bmp file.

When you click on the arrow in the Bitmap attribute Value field, you can choose from the following options:

Select Bitmap: Launches an Open dialog that you can use to locate and select the existing *.bmp file to be placed in the button.

Edit Bitmap: Launches an Open dialog that you can use to locate and select the existing *.bmp file to be opened in the Bitmap Editor. You can modify the bitmap and save it. The bitmap is then displayed in the button.

New Bitmap: Opens the Bitmap Editor which you can use to create and save a bitmap. When you save the new bitmap, it is displayed in the button.

In the generated *.pro file, this value is specified with the VALUE and Bitmap keyword to the widget creation routine.

Label

The Label attribute specifies the text label for a button. If you set the Type attribute to Bitmap (for push buttons only), this value is not displayed. For radio buttons and checkboxes, the label value is the text string displayed next to the button. By default, this value is set to Button, and you can change it to any string.

In the generated *.pro file, this value is specified with the VALUE keyword to the widget creation routine.

No Release

The No Release attribute enables and disables the dispatching of button release events for radio buttons and checkboxes. Normal buttons do not generate events when released, but radio buttons and checkboxes can return separate events for the select and release actions.

True: The release event is not returned; only the select event is returned. This is the default setting.

False: Both the release and select events are returned.

In the generated *.pro file, this values is specified with the NO_RELEASE keyword to the widget creation routine.

Tab Mode

The Tab Mode attribute specifies what support the widget has for receiving or losing focus through tabbing. By default, this value is set to Inherit.

Table I-36: Allowable Tab Mode Values

Table I-36: Allowable Tab Mode Values
Value	Description
Inherit	Upon creation, the widget inherits the tabbing support of the parent base.
None	Disallow tabbing into or out of the widget.
In and Out	Allow tabbing into and out of the widget.
In Only	Allow tabbing into the widget only.
Out Only	Allow tabbing off of the widget only.

In the generated *.pro file, this value is specified with the TAB_MODE keyword to the widget creation routine. For more information on tabbing among widgets, see Tabbing in Widget Applications.

Tooltip

The Tooltip attribute specifies a short text string that will be displayed when the mouse cursor is positioned over the button. The length of the tooltip is not explicitly limited, but since tooltips are displayed in a single line, it is best to keep the text short.

Type

Push: The button widget is a plain push button. This is the default value.

Menu: The button contains a menu. After you select this value, you can right-click on the button widget, choose Edit Menu, and define a menu to display, using the Menu Editor. See Using the Menu Editor for details on using the Menu Editor.

Bitmap: The button displays a bitmap, which you would use to create a toolbar for example. If you change the Type value to Bitmap, the Bitmap attribute is displayed and you can select, modify, or create a bitmap to display on the button.

In the generated *.pro file, this value is specified with the MENU or VALUE keywords to the widget creation routine.

Button, Radio Button, and Checkbox Widget Events

For button widgets, you can set common event properties and button-specific event properties. By default, event values are not set. For a list of events common to all widgets, see Common Events.

The following is the event property specific to button widgets; it applies to push buttons, radio buttons, and checkboxes:

OnButtonPress

The OnButtonPress value is the routine that is called when the button is pressed, or when a button is released for a radio button or checkbox button. In the generated *_eventcb.pro file, the event calling sequence looks like this:

where RoutineName is the name of the event procedure you specify. Event is the returned event structure, which is of the following type:

SELECT is set to 1 if the button was set, and 0 if released. Push buttons do not generate events when released, so SELECT will always be 1 for a push button. However, radio buttons and checkboxes are toggle buttons, and thus return separate events for the set and the release actions. To control whether or not release events are returned, set the No Release attribute.