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4D v14.3

LISTBOX Get information


LISTBOX Get information ( {* ;} object ; info ) -> Function result

Parameter	Type	Description
*	Operator	If specified, object is an object name (string) If omitted, object is a variable
object	Form object	Object name (if * is specified) or Variable (if * is omitted)
info	Longint	Information to get
Function result	Longint	Current value

Description

The LISTBOX Get information command returns various information regarding the current visibility and size of headers, footers and scrollbars in the list box object set using the object and * parameters.

If you pass the optional * parameter, you indicate that the object parameter is an object name (string). If you do not pass this parameter, you indicate that the object parameter is a variable. In this case, you pass a variable reference instead of a string. For more information about object names, refer to the Object Properties section.

In the info parameter, pass a value indicating the type of information that you want to get. You can use a value or one of the following constants from the “List Box” theme:

Constant	Type	Value	Comment
Listbox display footer	Longint	8	0=hidden, 1=shown
Listbox display header	Longint	0	0=hidden, 1=shown
Listbox display hor scrollbar	Longint	2	0=hidden, 1=shown
Listbox display ver scrollbar	Longint	4	0=hidden, 1=shown
Listbox footer height	Longint	9	Height in pixels
Listbox header height	Longint	1	Height in pixels
Listbox hor scrollbar height	Longint	3	Height in pixels
Listbox hor scrollbar position	Longint	6	Position of the cursor in pixels
Listbox ver scrollbar position	Longint	7	Position of the cursor in pixels
Listbox ver scrollbar width	Longint	5	Width in pixels

The first constants are useful for calculating the actual size of a list box area in a form.
When you use the constants Position listbox hor scrollbar or Position listbox ver scrollbar, the LISTBOX Get information command returns the position of the scrolling cursor in relation to its original position, i.e. the size of the hidden part of the window, expressed in pixels. By default, this position corresponds to 0. Combined, for example, with information concerning the row height, this value lets you find out the contents displayed in the listbox.
The statement LISTBOX Get information(vLB;Listbox footer height) returns the same value as the LISTBOX Get footers height command when footers are displayed. However, if footers are not displayed, LISTBOX Get information returns 0 while LISTBOX Get footers height still returns the height, in this case theoretical, of the footers.

Example

Given a list box containing rows with a height of 20 pixels each. You execute the following statement:

$scroll:=LISTBOX Get information(*;"Listbox";Position listbox ver scrollbar)

If, for instance, $scroll returns 200, you can conclude that the 11th row is currently the first one displayed in the list box (200/20=10, thus 10 rows are hidden).