ListBox Control
The listbox control provides a simple listing of string and or images. One or more may be selected. Horizontal and vertical scrollbars are available to help view the list. Multiple columns are also supported. Automatic sorting of items is provided.

Arguments
The Control Add statement is used to create all new controls. Here are the statement's arguments and any special significance to the listbox control.

Usage Notes
Some of these comments refer to the ListBox-specific statement in the next section below.

The ListBox is limited to 32,767 items.

Indexing is starts at 1 for all Control and Listbox statements.

Item numbers and returned item numbers are long integers.

To change an item and sort the results, use Delete/Add instead of Set Text.

To add an item and sort the results, use Add instead of Insert.

To change number of columns, send the %lb_setcolumnwidth message to the listbox using the Control Send statement, which assigns the column widths (NOT the number of columns). 

    Control Send hdlg, 504, %lb_setcolumnwidth, 50, 0

Using a horizontal scroll bar requires sending %lb_sethorizontalextent with Control Send to the listbox. Then use %ws_hscroll and %lbs_disablenoscroll in style& to make the horizontal scroll visible at all times.

Using %ws_vscroll in style& enables vertical scrollbar if list is too long. Use with %lbs_disablenoscroll in style& to make the vertical scroll visible at all times.

By default, the listbox height resizes to integral multiples of a list item. Use %lbl_nointegralheight in style& to force the listbox to the exact size specified in the Control Add Listbox statement.

ListBox-Specific PowerBASIC Statements
PowerBASIC provides several statements specific to the listbox control. These allow the application to manage the content and display of the control.

See the Usage section above for information on how to use the values made available by these statements.

Messages, Notifications, Styles, and ExtSstyles
There are four types of named constants in the following table. All are pulled from the MSDN web site.

The first column contains control-specific named constants and the second column contains generic window named constants (listbox controls are windows).

Also, if the PowerBASIC Help file has an entry on the value, it is highlighted in yellow. If the value was noted in PowerBASIC Help as a default value, it is also shown in bold text.

In the values for notifications, descriptions starting with -n and -c refer to events received through the %wm_notify and %wm_command messages. By default, PowerBASIC controls can receive both of these messages.

   

And here is a short description of many of the named constants corresponding to notifications, styles, and extstyle - particularly those discussed in the PowerBASIC Help topics. 

    %lbn_dblclk            -c doubleclick
    %lbn_errspace          -c not enough memory
    %lbn_killfocus         -c keyboard focus lost
    %lbn_selcancel         -c ignore initial user selection
    %lbn_selchange         -c selection about to be changed (arrow or mouse)
    %lbn_setfocus          -c keyboard focus received
    %lbs_disablenoscroll   - show vertical scrollbar (disable if not needed)
    %lbs_extendedsel       - allow multiple selection (SHIFT+mouse)
    %lbs_multicolumn       - multi-column list box. scroll horizontally. 
    %lbs_multiplesel       - allow multiple selection (SHIFT not needed)
    %lbs_nointegralheight  - use exact size (partial display of lines)
    %lbs_nosel             - disallow list box selection (can view)
    %lbs_notify            - send click/dbl-click messages
    %lbs_sort              - automatically sort list
    %lbs_standard          - combination of %_sort/notify/vscroll/border
    %lbs_usetabstops       - expand tabs to tabstop positions
    %wm_chartoitem         - response to wm_char (lbs_wantkeyboardinput style only)
    %wm_ctlcolorlistbox    - before system draws list box
    %wm_deleteitem         - when listbox destroyed or item deleted 
    %wm_vkeytoitem         - response to wm_keydown (lbs_wantkeyboardinput style only)
    %ws_border             - use thin line border
    %ws_ex_clientedge      - apply sunken edge border
    %ws_ex_left            - generic left-aligned properties
    %ws_ex_right           - generic right-aligned properties
    %ws_ex_staticedge      - apply 3D border
    %ws_ex_transparent     - draw controls/windows beneath control first
    %ws_ex_windowedge      - apply raised edge border
    %ws_group              - starts/ends group. use %ws_tabstop style.
    %ws_hscroll            - autodisplay horizontal scroll
    %ws_tabstop            - allows receipt of keyboard focus
    %ws_vscroll            - autodisplay vertical scroll

Callback Function
A control can have its own callback function, or use the parent dialog callback function.

A control callback function should return TRUE to indicate it has processed the message. This prevents unnecessarily calling the dialog callback function, which will process the message if no control callback function is available, or if the control callback function returns FALSE.

By default, both %WM_COMMAND and %WM_NOTIFY messages are received. However, if the #MESSAGE COMMAND compiler directive is invoked, the %WM_NOTIFY messages will not be available.

In addition, %lbs_notify must be included in style& to receive the %lbn_dblclk messages.

Here's a sample listbox control callback function. 

   CallBack Function cbListBox()
      Select Case CB.MSG
         Case %WM_COMMAND
            Select Case CB.CTLMSG
               Case %lbn_dblclk      'doubleclick
               Case %lbn_errspace    'not enough memory
               Case %lbn_killfocus   'keyboard focus lost
               Case %lbn_selcancel   'ignore initial user selection
               Case %lbn_selchange   'selection about to be changed (arrow or mouse)
               Case %lbn_setfocus    'keyboard focus received
         End Select
      End Select
   End Function

In each Case section, add the statements the application needs to respond to the event. Also, be sure to add "Function=1" as appropriate to indicate that the event was handled by the callback function.

Issues
Help mentions that listboxes can contain images, but no information is provided on how to add the images. There are two samples apps distributed with PowerBASIC but with little explanation.

The %lbs_notify says it affect click and dblclk, but there is no click event listed as available.

I'll update this page as more information becomes available.

CONTROL Statement Syntax
The following table lists the various Control statements (except the ADD statements). Most, but not all, can be used with the listbox control. A one-line description of the statement and then its syntax are presented.

If you have any suggestions or corrections, please let me know.