EnableExplicit

Define a
Define lvi.LV_ITEM

Procedure SelectAllItems(gad, selState)
  Protected lvi.LV_ITEM
  
  lvi.LV_ITEM
  lvi\mask = #LVIF_STATE
  lvi\stateMask = #LVIS_STATEIMAGEMASK
  lvi\state = selState <<12
  SendMessage_(GadgetID(gad), #LVM_SETITEMSTATE, 1, lvi)
EndProcedure

If OpenWindow(0,0,0,500,250,"Window",#PB_Window_SystemMenu|#PB_Window_ScreenCentered)
  ListIconGadget(1,10,10,480,230,"Spalte",400,#PB_ListIcon_CheckBoxes)
  
  For a=1 To 5
    AddGadgetItem(1,-1,"Item",0,0)
  Next
  
  lvi.LV_ITEM
  lvi\mask = #LVIF_STATE
  lvi\stateMask = #LVIS_STATEIMAGEMASK
  lvi\state = #LVIS_SELECTED <<12;#LVIS_FOCUSED
  SendMessage_(GadgetID(1), #LVM_SETITEMSTATE, 1, lvi)
  
Repeat : Until WaitWindowEvent() = #PB_Event_CloseWindow
EndIf