Tech Tip: Programmatically disable sorting in listbox

PRODUCT: 4D | VERSION: 14.3 | PLATFORM: Mac & Win

Published On: March 16, 2015

Listbox columns have the ability to be sorted if the following conditions are fulfilled.

Listbox display header is checked
Listbox column has the sortable property checked
Listbox On header clicked event is checked

Columns in the listbox can also disable sorting programmatically. To do so, in the listbox's On Header Clicked form event; return -1 to prevent the sort:

Case of
:(Form event=On Header Click)
$0:=-1 //disable sort
End case

To programtically re-enable the sort, $0 can be set to 0.

Below is an example of disabling the first column from being sorted, while allowing other columns to be sorted:

//Listbox Object Method
Case of
  : (Form event=On Header Click)
    C_TEXT($varName)
    C_LONGINT($tableNum;$fieldNum)
    RESOLVE POINTER(Self;$varName;$tableNum;$fieldNum)
    If ($varName="Header1")
      $0:=-1
    Else
      $0:=0
    end if
End Case