How to paint the background color in special level in TVirtualStringTree

Question

I try to paint a hightline text using backgroundcolor in all sepecial level of VirtualStringTree. It look like a selected nodes for all same level. The code below doesn't work. Please someone give a direction.

procedure TMainForm.Tree1PaintText(Sender: TBaseVirtualTree; const TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex; TextType: TVSTTextType);
var  Data: PNodeData;LEVEL:INTEGER;  tree1node,tree4Node: PVirtualNode;
begin 
    Data := Tree1.GetNodeData(Node);
    Level := tree1.GetNodeLevel(node);

 case column of
     0:begin
        if Level = 0 then BEGIN
               TargetCanvas.Font.Style := TargetCanvas.Font.Style + [fsBold];
               TargetCanvas.Font.Color :=CLyellow;
               targetcanvas.Brush.Color :=clgreen;//don't work
               targetcanvas.Brush.Style :=bssolid;     

             END;
            if  Level = 1 then BEGIN
                  TargetCanvas.Font.Color :=CLaqua; 
                  targetcanvas.Brush.Color :=clgreen;
            end;
       end;

Answer 1

VT fills the cell background sooner, in the PrepareCell method to be more specific. So it's too late for attempts to setup the canvas brush. Try to fill the node rectangle from the OnBeforeCellPaint event instead:

procedure TForm1.VirtualStringTree1BeforeCellPaint(Sender: TBaseVirtualTree;
  TargetCanvas: TCanvas; Node: PVirtualNode; Column: TColumnIndex;
  CellPaintMode: TVTCellPaintMode; CellRect: TRect; var ContentRect: TRect);
var
  R: TRect;
begin
  if CellPaintMode = cpmPaint then
  begin
    R := Sender.GetDisplayRect(Node, Column, True, False, True);
    R.Offset(0, -R.Top);
    case Sender.GetNodeLevel(Node) of
      0: TargetCanvas.Brush.Color := $0000F9FF;
      1: TargetCanvas.Brush.Color := $0000BFFF;
      2: TargetCanvas.Brush.Color := $000086FF;
    end;
    TargetCanvas.FillRect(R);
  end;
end;

Preview:

Answer 2

One way is to use eaColor as erase action in OnBeforeItemErase event:

procedure TMainForm.Tree1BeforeItemErase(Sender: TBaseVirtualTree; TargetCanvas: TCanvas;
          Node: PVirtualNode; ItemRect: TRect; var ItemColor: TColor; var EraseAction: TItemEraseAction);
begin
   if not Sender.Selected[Node] then begin
      case Sender.GetNodeLevel(Node) of
        0: ItemColor := clgreen;
        1: ItemColor := clAgua;
      end;
      EraseAction := eaColor;
   end;
end;