Display Custom Hints for TListView Sub Items

You use the TListView Delphi control to display a list of items in a fashion similar to how Windows Explorer displays files and folders. The items can be displayed in columns with column headers and sub-i items, or vertically or horizontally, with small or large icons.

ListView Item Hints?

The TListView exposes the Hint and ShowHint properties you use to set up whether the hint (tooltip) should be displayed for the control when the mouse hovers over it.

TListView Sub Item Hints

In most situations, when using the list view, you will need custom hints to be displayed for every list view item. What's more, a custom hint for every list view sub item might be required.

ListView provides the OnInfoTip event which gets fired when the mouse is paused over an item in the list view.
By default, when hints are enabled (that is, when ShowHint is true), the list view displays the hint specified by its Hint property. OnInfoTip allows the list view to override this value to specify a hint that is specific to the item under the mouse.

When ViewStyle is set to vsReport the ListView displays each item on its own line with information (sub items) arranged in columns.

Unfortunately, the OnInfoTip is not fired when the mouse pauses over a sub-item.

To force a list view to display custom hints for items and sub items, you need to handle two events: OnInfoTip and OnMouseMove. Here's the implementation of the OnInfoTip event handler.

 procedure TLVHintsForm.ListView1InfoTip(Sender: TObject; Item: TListItem; var InfoTip: string) ;
 begin
   //Show the "full" item - with all the sub items
   InfoTip := InfoTip + #13#10 + item.SubItems[0] + #13#10 + item.SubItems[1];
 end;
 

To show custom hints for every sub-item, you need to handle the OnMouseMove event.

 uses CommCtrl ... 
procedure TLVHintsForm.ListView1MouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer) ;
 var
   pt: TPoint;
   li : TLIstItem;
   lvHitInfo: TLVHitTestInfo;
   hint : string;
 begin
   pt := ListView1.ScreenToClient(Mouse.CursorPos) ;
   li := ListView1.GetItemAt(pt.x, pt.y) ;
 
   //over a sub item?
   if li = nil then
   begin
     FillChar(lvHitInfo, SizeOf(lvHitInfo), 0) ;
     lvHitInfo.pt := pt;
     //over a sub item!
     if -1 <> ListView1.Perform(LVM_SUBITEMHITTEST, 0, LParam(@lvHitInfo)) then
     begin
       hint := Format('Name: %s, %s : %s',[
         ListView1.Items[lvHitInfo.iItem].Caption,
         ListView1.Columns[lvHitInfo.iSubItem].Caption,
         ListView1.Items[lvHitInfo.iItem].SubItems[-1 + lvHitInfo.iSubItem]]) ;
 
       if hint <> Memo1.Lines[0] then
       begin
         Memo1.Lines.Insert(0, hint) ;
         //activate hint
         ListView1.Hint := hint;
         Application.ActivateHint(Mouse.CursorPos) ;
       end;
    end;
   end;
 end;
 

After getting the Mouse position (Mouse.CursorPos), using ScreenToClient we get the position of the mouse in ListView1's coordinates.

Sending the LVM_SUBITEMHITTEST message to the list view fills the (list view specific) TLVHitTestInfo record. This structure helps us find which list view item or subitem is at a given position.

If the mouse is over a sub-item, we activate the hint window by calling the Application.ActivateHint method.

That's it, really.