Control Add Check3State

[Gary Beene]

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PB/WIN - CONTROL ADD CHECK3STATE statement

Purpose

Add an auto 3-state checkbox to a dialog. This is commonly used to indicate a selection that may be True (set or checked), False (unset or cleared) or Indeterminate (grayed), and is often found in dialogs that provide "multiple choice" options.

Syntax

CONTROL ADD CHECK3STATE, hDlg, id&, txt$, x, y, xx, yy [, [style&] [, [exstyle&]]] [[,] CALL callback]

hDlg

Handle of the dialog in which the 3-state checkbox 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 %AutoLogoff equate 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 in the 3-state checkbox. 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.

xx

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.

yy

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 3-state checkbox control. The default 3-state checkbox style comprises %BS_LEFT, %BS_VCENTER, and %WS_TABSTOP. The default style is used only if both the primary and extended style parameters are omitted from the statement. For example:

CONTROL ADD CHECK3STATE, hDlg, id&, txt$, 100, 100, 40, 14, , , _
  CALL Check3Callback() ' Use default styles

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

The primary 3-state checkbox 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_FLAT

Create a flat control (without the raised 3D look).

%BS_LEFT

Place the text on the left side of the checkbox. Also see %BS_LEFTTEXT. (default)

%BS_LEFTTEXT

Place the checkbox to the right of the text portion of the control. Combine with %BS_RIGHT to right-align text against the left side of the checkbox control.

%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 a control to send the %BN_KILLFOCUS and %BN_SETFOCUS messages to the callback.

%BS_PUSHLIKE

Button state alternates (toggles) between normal (raised) and depressed (sunken) modes.

%BS_RIGHT

Place the text on the right side of the checkbox. 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 3-state checkbox 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 3-state checkbox control. The default extended 3-state checkbox 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 CHECK3STATE statement, in the same manner as style& above.

The extended 3-state checkbox 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.

In general, if the control 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

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 "click" a control, simply by pressing and holding the ALT key while pressing the specified hot-key. For example, "Set s&tate" makes ALT+t the hot-key.

When the user clicks a 3-state checkbox, a message is sent to the Callback Function designated for the control. If there is no Callback Function designated, the message is sent to the callback for the dialog.

If the control callback processes the notification message, it should return TRUE (non-zero) to prevent the message being passed needlessly to the dialog callback, and eventually to the DDT engine itself.

Notification messages are sent to the Callback Function, with CB.MSG = %WM_COMMAND, CB.CTL holding the ID (id&) of the control, and CB.CTLMSG holding the following values:

%BN_CLICKED

Sent when the user clicks a mouse button, or activates the control with the hot-key (unless the control has been disabled).

%BN_DISABLE

Sent when a control is disabled.

%BN_KILLFOCUS

Sent when a control loses the keyboard focus. The control must include the %BS_NOTIFY style.

%BN_SETFOCUS

Sent when a control receives the keyboard focus. The control must include 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.

See Also

Dynamic Dialog Tools, CONTROL ADD CHECKBOX, CONTROL ADD OPTION, CONTROL GET CHECK, CONTROL SET CHECK, CONTROL SET COLOR, CONTROL SET FONT

References

Integral:

Double-word (???)
Integers (%)
Long integers (&)
Quad integers (&&)
Word (??)