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unit CheckTreeview;

interface

uses
  Windows, Messages, SysUtils, Classes, Controls,Commctrl,ComCtrls;
const
   TVIS_CHECKED = $2000;
type
  TCheckTreeview = class(TTreeView)
  private
    { Private declarations }
  protected
    { Protected declarations }
    procedure CreateParams(var Params: TCreateParams); override;
  public
    { Public declarations }
    function IsChecked(Node :TTreeNode) :Boolean;
    procedure SetChecked(Node :TTreeNode; Checked :Boolean);
  published
    { Published declarations }
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('Standard', [TCheckTreeview]);
end;

{ TCheckTreeview }

procedure TCheckTreeview.CreateParams(var Params: TCreateParams);
begin
  inherited;
  Params.Style:=Params.Style or TVS_CHECKBOXES;
end;

function TCheckTreeview.IsChecked(Node: TTreeNode): Boolean;
var
  TvItem :TTVItem;
begin
  TvItem.Mask  := TVIF_STATE;
  TvItem.hItem := Node.ItemId;
  TreeView_GetItem(Node.TreeView.Handle, TvItem);
  Result := (TvItem.State and TVIS_CHECKED) = TVIS_CHECKED;
end;

procedure TCheckTreeview.SetChecked(Node: TTreeNode; Checked: Boolean);
var
  TvItem :TTVItem;
begin
  FillChar(TvItem, SizeOf(TvItem), 0);
  with TvItem do begin
    hItem     := Node.ItemId;
    Mask      := TVIF_STATE;
    StateMask := TVIS_STATEIMAGEMASK;
    if Checked then
      TvItem.State :=TVIS_CHECKED
    else
      TvItem.State :=TVIS_CHECKED shr 1;
    TreeView_SetItem(Node.TreeView.Handle, TvItem);
  end;
end;
end.