delphi 在 DragDrop 的时候，滚动 TreeView

在 DragDrop 的时候，滚动 TreeView

当高度不够的时候

 
 
procedure TForm1.TreeView1DragOver(Sender, Source: TObject; X, Y: Integer;
  State: TDragState; var Accept: Boolean);
begin
   if (y < 15) then
    {On the upper edge - should scroll up }
     SendMessage(TreeView1.Handle, WM_VSCROLL, SB_LINEUP, 0)
   else if (TreeView1.Height - y < 15) then
    { On the lower edge - should scroll down }
      SendMessage(TreeView1.Handle, WM_VSCROLL, SB_LINEDOWN, 0);
 
 
 
    Accept := Source = Sender;
     if not Accept then exit;
end;

来自为知笔记(Wiz)