CONTROL ADD TREEVIEW statement

Purpose

Add a TreeView control to a dialog. A TreeView displays a set of string data items with a parent-child relationship between the items. This creates a hierarchical list of data which can have any number of levels. The user may view the items, selecting them for use in the program at a later time.

Syntax

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

hDlg

Handle of the dialog in which the TreeView 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 %PickList 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 associate with the TreeView control. A TreeView control does not display this text, so it is common to set this value to a null, empty string literal ("").

x,y

Integer 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,yy

Integral expressions, variable, or numeric literal values, specifying the width and height of the control. xx is the width and yy is the height, given in the same terms (pixels or dialog units) as the parent dialog.

style&

Primary style of the TreeView control. The default TreeView style comprises %WS_TABSTOP, %TVS_HASBUTTONS, %TVS_LINESATROOT, %TVS_HASLINES, and %TVS_SHOWSELALWAYS. This default TreeView style is used if the style parameters are omitted from the statement, as in the following example:

CONTROL ADD TREEVIEW, hDlg, id&, "", 100, 100, 150, 200, , , CALL TVCallback()

If you include explicit style values, they replace the default values. That is, they are not added to the default styles values - your code must specify all necessary primary and extended style parameters.

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

%TVS_HASBUTTONS	Displays +- signs next to parent items so the user can expand or collapse a list of child items.
%TVS_HASLINES	Uses lines to show the hierarchy of data items.
%TVS_LINESATROOT	Uses lines to link items at the root level.
%TVS_EDITLABELS	Allows the user to edit the labels of the data items.
%TVS_DISABLEDRAGDROP	Prevents drag and drop
%TVS_SHOWSELALWAYS	A selected item remains selected when the control loses focus.
%TVS_NOTOOLTIPS	Disables ToolTips.
%TVS_CHECKBOXES	Enables check boxes for items with an image.
%TVS_TRACKSELECT	Enables hot tracking.
%TVS_SINGLEEXPAND	Only one item can be expanded at a time.
%TVS_INFOTIP	Obtains ToolTip information.
%TVS_FULLROWSELECT	The entire row of a selected item is highlighted.
%TVS_NOSCROLL	Disables horizontal and vertical scrolling.
%TVS_NONEVENHEIGHT	Sets the height of items to an odd height.
%TVS_NOHSCROLL	Disables horizontal scrolling.
%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.
%WS_TABSTOP	Allow the 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.

exstyle&

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

The extended TreeView 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

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 messages.