procedure NextRow(Select: Boolean);
  begin
    with FDatalink.Dataset do
    begin
      if (State = dsInsert) and not Modified and not FDatalink.FModified then
        if EOF then Exit else Cancel
      else
        DoSelection(Select, 1);
      if EOF and CanModify and (not ReadOnly) and (dgEditing in Options) then
        Append;
    end;
  end;

  procedure PriorRow(Select: Boolean);
  begin
    with FDatalink.Dataset do
      if (State = dsInsert) and not Modified and EOF and
        not FDatalink.FModified then
        Cancel
      else
        DoSelection(Select, -1);
  end;

  procedure Tab(GoForward: Boolean);
  var
    ACol, Original: Integer;
  begin
    ACol := IIF(FVertical, Row, Col);
    Original := ACol;
    BeginUpdate;    { Prevent highlight flicker on tab to next/prior row }
    try
      while True do
      begin
        if GoForward then
          Inc(ACol) else
          Dec(ACol);
        if ACol >= IIF(FVertical, RowCount, ColCount) then
        begin
          NextRow(False);
          ACol := FIndicatorOffset;
        end
        else if ACol < FIndicatorOffset then
        begin
          PriorRow(False);
          ACol := IIF(FVertical, RowCount, ColCount);
        end;
        if ACol = Original then Exit;
        if FVertical then
          begin
          if TabStopRow(ACol) then
             begin
             MoveCol(ACol);
             Exit;
             end;
          end
        else
        if TabStops[ACol] then
          begin
          MoveCol(ACol);
          Exit;
          end;
      end;
    finally
      EndUpdate;
    end;
  end;

  function DeletePrompt: Boolean;
  var
    Msg: string;
  begin
    if (FBookmarks.Count > 1) then
      Msg := SDeleteMultipleRecordsQuestion
    else
      Msg := SDeleteRecordQuestion;
    Result := not (dgConfirmDelete in Options) or
      (MessageDlg(Msg, mtConfirmation, mbOKCancel, 0) <> idCancel);
  end;

const
  RowMovementKeys = [VK_UP, VK_PRIOR, VK_DOWN, VK_NEXT, VK_HOME, VK_END];

begin
  KeyDownEvent := OnKeyDown;
  if Assigned(KeyDownEvent) then KeyDownEvent(Self, Key, Shift);
  if not FDatalink.Active or not CanGridAcceptKey(Key, Shift) then Exit;
  with FDatalink.DataSet do
  
   if FVertical then
    if ssCtrl in Shift then
    begin
      if (Key in RowMovementKeys) then ClearSelection;
      case Key of
        VK_LEFT, VK_PRIOR: MoveBy(-FDatalink.ActiveRecord);
        VK_RIGHT, VK_NEXT: MoveBy(FDatalink.BufferCount - FDatalink.ActiveRecord - 1);
        VK_UP: MoveCol(FIndicatorOffset);
        VK_DOWN: MoveCol(RowCount - 1);
        VK_HOME: First;
        VK_END: Last;
        VK_DELETE:
          if (not ReadOnly) and not IsEmpty
            and CanModify and DeletePrompt then
          if FBookmarks.Count > 0 then
            FBookmarks.Delete
          else
            Delete;
      end
    end
    else
      case Key of
        VK_LEFT: PriorRow(True);
        VK_RIGHT: NextRow(True);
        VK_UP:
          if dgRowSelect in Options then
            PriorRow(False) else
            MoveCol(Row - 1);
        VK_DOWN:
          if dgRowSelect in Options then
            NextRow(False) else
            MoveCol(Row + 1);
        VK_HOME:
          if (RowCount = FIndicatorOffset+1)
            or (dgRowSelect in Options) then
          begin
            ClearSelection;
            First;
          end
          else
            MoveCol(FIndicatorOffset);
        VK_END:
          if (RowCount = FIndicatorOffset+1)
            or (dgRowSelect in Options) then
          begin
            ClearSelection;
            Last;
          end
          else
            MoveCol(RowCount - 1);
        VK_NEXT:
          begin
            ClearSelection;
            MoveBy(VisibleColCount);
          end;
     

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