CONTROL ADD OPTION statement

Purpose

Add an option button to a dialog. An option button is just like a conventional "radio button" control.

Syntax

CONTROL ADD OPTION, hDlg, id&, txt$, x, y, xx, yy [, [style&] [, [exstyle&]]] [[,] CALL callback]

hDlg

Handle of the dialog in which the option button will be created. The dialog will become the parent of the control.

id&

Unique identifier for the control in the range 1 to 65535, frequently specified with numeric equates for clarity of the code. For example, the equate %DefCon5 is more informative than a literal value such as 497. Best practice suggests identifiers should start at 100 to avoid conflict with any of the standard predefined identifiers.

txt$

Text to be displayed next to the option button. An ampersand (&) may be included in txt$ to specify a hot-key. See the Remarks section below.

x, y

Integral expressions, variables, or numeric literal values, specifying the location of the control inside the dialog client area. x is the horizontal position, and y is the vertical position. 0,0 refers to the upper left corner of the dialog box client area. Coordinates are specified in the same terms (pixels or dialog units) as the parent dialog.

Integral expression, variable, or numeric literal value, specifying the width of the control. The width is given in the same terms (pixels or dialog units) as the parent dialog. The most common value used in the Microsoft Dialog Editor and Visual Studio is 40 dialog units.

Integral expression, variable, or numeric literal value, specifying the height of the control. The height is given in the same terms (pixels or dialog units) as the parent dialog. The most common value used in the Microsoft Dialog Editor and Visual Studio is 14 dialog units.

style&

Primary style of the option button control. The default option button styles are %WS_TABSTOP, %BS_LEFT, and %BS_VCENTER. The default styles are used if both the primary and extended style parameters are omitted from the statement. For example:

CONTROL ADD OPTION, hDlg, id&, txt$, 100, 100, 150, 200, , , _

CALL OptionButtonCallback() ' Use default styles

Custom style values replace the default values. That is, they are not in addition to the default style values - your code must specify all necessary primary and extended style parameters.

The primary option button style value can be a combination of any values below, combined together with the OR operator to form a bitmask:

%BS_BOTTOM	Place the text at the bottom of the control.
%BS_CENTER	Center the text horizontally in the control.
%BS_LEFT	Place the text on the left side of the control. Also see %BS_LEFTTEXT. (default)
%BS_LEFTTEXT	Place the option button to the right of the text portion of the control. Combine with %BS_RIGHT to right-align text against the left side of the option button.
%BS_MULTILINE	Wrap the caption text across multiple lines, if the text string is too long to fit on a single line. To force a wrap, insert a $CR (or $CRLF) into the caption text at the desired wrap position.
%BS_NOTIFY	Enable the %BN_KILLFOCUS and %BN_SETFOCUS notification messages for the option button.
%BS_PUSHLIKE	Button state alternates (toggles) between normal (raised) and depressed (sunken) modes.
%BS_RIGHT	Place the text on the right side of the control. Also see %BS_LEFTTEXT.
%BS_TOP	Place the text at the top of the control.
%BS_VCENTER	Center the text vertically in the control. (default)
%WS_DISABLED	Create a control that is initially disabled. A disabled control cannot receive input from the user.
%WS_GROUP	Define the start of a group of controls. The first control in each group should also use %WS_TABSTOP style. The next %WS_GROUP control in the tab order defines the end of this group and the start of a new group. Groups configured this way permit the arrow keys to shift focus between the controls within the group, and focus can jump from group to group with the usual TAB and SHIFT+TAB keys. Both tab stops and groups are permitted to wrap from the end of the tab order back to the start.
%WS_TABSTOP	Allow the option control to receive keyboard focus when the user presses the TAB and SHIFT+TAB keys. The TAB key shifts keyboard focus to the next control with the %WS_TABSTOP style, and SHIFT+TAB shifts focus to the previous control with %WS_TABSTOP. (default)

exstyle&

Extended style of the option button control. The default extended option button style comprises %WS_EX_LEFT. The default extended style is used if both the primary and extended style parameters are omitted from the CONTROL ADD OPTION statement completely, in the same manner as style& above.

The extended option button style value can be a combination of any values below, combined together with the OR operator to form a bitmask:

%WS_EX_CLIENTEDGE	Apply a sunken edge border to the control.
%WS_EX_LEFT	The control has generic "left-aligned" properties. (default)
%WS_EX_RIGHT	The control has generic "right-aligned" properties. This style has an effect only if the shell language is Hebrew, Arabic, or another language that supports reading order alignment; otherwise, the style is ignored.
%WS_EX_STATICEDGE	Apply a three-dimensional border style to the control (intended to be used for items that do not accept user input).
%WS_EX_TRANSPARENT	Controls/windows beneath the control are drawn before the control is drawn. The control is deemed transparent because elements behind the control have already been painted - the control itself is not drawn differently. True transparency is achieved by using Regions - see MSDN for more information.
%WS_EX_WINDOWEDGE	Apply a raised edge border to the control.

callback

Optional name of a Callback Function that receives all %WM_COMMAND and %WM_NOTIFY messages for the control. See the #MESSAGES metastatement to choose which messages will be received. If a callback for the control is not designated, you must create a dialog Callback Function to process messages from your control.

If the Callback Function processes a message, it should return TRUE (non-zero) to prevent the message being passed unnecessarily to the dialog callback (if one exists). The dialog callback should also return TRUE if the notification message is processed by that Callback Function. Otherwise, the DDT engine processes unhandled messages.

Remarks

Option buttons are used for presenting a list of choices, only one of which may be selected. So, there is no point in having just a single option button. If what you want is to allow turning a single item on or off, use a Checkbox instead.

When a group of option buttons are created, you should explicitly set the "selected" and "unselected" state of all option buttons, using the CONTROL SET OPTION statement to set the Check State of all the buttons in the group.

In addition, the first OPTION control in a group should have the style %WS_GROUP (to mark the beginning of a group of buttons) and %WS_TABSTOP. The remainder of the OPTION controls in the group should not have %WS_GROUP or %WS_TABSTOP styles. However, the very next non-OPTION control to appear in the tab order after the group should be given the %WS_GROUP and %WS_TABSTOP styles (the latter may depend on the type of control it is). If there are no other controls after the group, add %WS_GROUP to the first control in the dialog. This ensures that keyboard navigation with the arrow keys will operate within the group of OPTION controls, and that the TAB and SHIFT+TAB keys will switch focus between whole groups of controls (instead of individual controls as is common when each group member has the %WS_TABSTOP style).

If the ampersand (&) character appears in the txt$ parameter, the letter that follows will be displayed underscored. This adds a control accelerator (hot-key) to enable the user to directly select the Option control, simply by pressing and holding the ALT key while pressing the specified hot-key. For example, "Level &3" makes ALT+3 the hot-key.

When the user clicks an option button, a message is sent to the Callback Function designated for the control. If there is no Callback Function designated then the message is sent to the callback for the dialog.

The following notifications are sent to the Callback Function:

%BN_CLICKED	Sent when the user clicks a mouse button, or activates the button with the hot-key (unless the button has been disabled).
%BN_KILLFOCUS	Sent then the option button loses keyboard focus, provided the button has the %BS_NOTIFY style.
%BN_SETFOCUS	Sent when the option button receives keyboard focus, provided the option button has the %BS_NOTIFY style.

When a Callback Function receives a %WM_COMMAND message, it should explicitly test the value of CB.CTL and CB.CTLMSG to guarantee it is responding appropriately to the notification message.