pszType: LPCTSTR;       // IN/OUT: Name of a type of window
    fsValidMembers: DWORD;  // IN: Bit flag of valid members (HHWIN_PARAM_)
    fsWinProperties: DWORD; // IN/OUT: Properties/attributes of the window (HHWIN_)

    pszCaption: LPCTSTR;    // IN/OUT: Window title
    dwStyles: DWORD;        // IN/OUT: Window styles
    dwExStyles: DWORD;      // IN/OUT: Extended Window styles
    rcWindowPos: TRect;     // IN: Starting position, OUT: current position
    nShowState: Integer;    // IN: show state (e.g., SW_SHOW)

    hwndHelp: HWND;         // OUT: window handle
    hwndCaller: HWND;       // OUT: who called this window

    paInfoTypes: PHHInfoType; // IN: Pointer to an array of Information Types

    { The following members are only valid if HHWIN_PROP_TRI_PANE is set }

    hwndToolBar: HWND;      // OUT: toolbar window in tri-pane window
    hwndNavigation: HWND;   // OUT: navigation window in tri-pane window
    hwndHTML: HWND;         // OUT: window displaying HTML in tri-pane window
    iNavWidth: Integer;     // IN/OUT: width of navigation window
    rcHTML: TRect;          // OUT: HTML window coordinates

    pszToc: LPCTSTR;        // IN: Location of the table of contents file
    pszIndex: LPCTSTR;      // IN: Location of the index file
    pszFile: LPCTSTR;       // IN: Default location of the html file
    pszHome: LPCTSTR;       // IN/OUT: html file to display when Home button is clicked
    fsToolBarFlags: DWORD;  // IN: flags controling the appearance of the toolbar
    fNotExpanded: BOOL;     // IN: TRUE/FALSE to contract or expand, OUT: current state
    curNavType: Integer;    // IN/OUT: UI to display in the navigational pane
    tabpos: Integer;        // IN/OUT: HHWIN_NAVTAB_TOP, HHWIN_NAVTAB_LEFT, or HHWIN_NAVTAB_BOTTOM
    idNotify: Integer;      // IN: ID to use for WM_NOTIFY messages
    tabOrder: array[0..HH_MAX_TABS] of Byte; // IN/OUT: tab order: Contents, Index, Search, History, Favorites, Reserved 1-5, Custom tabs
    cHistory: Integer;      // IN/OUT: number of history items to keep (default is 30)
    pszJump1: LPCTSTR;      // Text for HHWIN_BUTTON_JUMP1
    pszJump2: LPCTSTR;      // Text for HHWIN_BUTTON_JUMP2
    pszUrlJump1: LPCTSTR;   // URL for HHWIN_BUTTON_JUMP1
    pszUrlJump2: LPCTSTR;   // URL for HHWIN_BUTTON_JUMP2
    rcMinSize: TRect;       // Minimum size for window (ignored in version 1)
    cbInfoTypes: Integer;   // size of paInfoTypes;
{$IFDEF HTMLHELP12}
    pszCustomTabs: LPCTSTR; // multiple zero-terminated Strings
{$ENDIF}
  end;
  {$EXTERNALSYM tagHH_WINTYPE}
  HH_WINTYPE = tagHH_WINTYPE;
  {$EXTERNALSYM HH_WINTYPE}
  PHH_WINTYPE = ^tagHH_WINTYPE;
  {$EXTERNALSYM PHH_WINTYPE}
  THHWinType = tagHH_WINTYPE;

const
  HHACT_TAB_CONTENTS  = 0;
  {$EXTERNALSYM HHACT_TAB_CONTENTS}
  HHACT_TAB_INDEX     = 1;
  {$EXTERNALSYM HHACT_TAB_INDEX}
  HHACT_TAB_SEARCH    = 2;
  {$EXTERNALSYM HHACT_TAB_SEARCH}
  HHACT_TAB_HISTORY   = 3;
  {$EXTERNALSYM HHACT_TAB_HISTORY}
  HHACT_TAB_FAVORITES = 4;
  {$EXTERNALSYM HHACT_TAB_FAVORITES}
  HHACT_EXPAND        = 5;
  {$EXTERNALSYM HHACT_EXPAND}
  HHACT_CONTRACT      = 6;
  {$EXTERNALSYM HHACT_CONTRACT}
  HHACT_BACK          = 7;
  {$EXTERNALSYM HHACT_BACK}
  HHACT_FORWARD       = 8;
  {$EXTERNALSYM HHACT_FORWARD}
  HHACT_STOP          = 9;
  {$EXTERNALSYM HHACT_STOP}
  HHACT_REFRESH       = 10;
  {$EXTERNALSYM HHACT_REFRESH}
  HHACT_HOME          = 11;
  {$EXTERNALSYM HHACT_HOME}
  HHACT_SYNC          = 12;
  {$EXTERNALSYM HHACT_SYNC}
  HHACT_OPTIONS       = 13;
  {$EXTERNALSYM HHACT_OPTIONS}
  HHACT_PRINT         = 14;
  {$EXTERNALSYM HHACT_PRINT}
  HHACT_HIGHLIGHT     = 15;
  {$EXTERNALSYM HHACT_HIGHLIGHT}
  HHACT_CUSTOMIZE     = 16;
  {$EXTERNALSYM HHACT_CUSTOMIZE}
  HHACT_JUMP1         = 17;
  {$EXTERNALSYM HHACT_JUMP1}
  HHACT_JUMP2         = 18;
  {$EXTERNALSYM HHACT_JUMP2}
  HHACT_ZOOM          = 19;
  {$EXTERNALSYM HHACT_ZOOM}
  HHACT_TOC_NEXT      = 20;
  {$EXTERNALSYM HHACT_TOC_NEXT}
  HHACT_TOC_PREV      = 21;
  {$EXTERNALSYM HHACT_TOC_PREV}
  HHACT_NOTES         = 22;
  {$EXTERNALSYM HHACT_NOTES}
  HHACT_LAST_ENUM     = 23;
  {$EXTERNALSYM HHACT_LAST_ENUM}

type
  PHHNTrack = ^THHNTrack;
  tagHHNTRACK = packed record
    hdr: NMHDR;
    pszCurUrl: PCSTR;        // Multi-byte, null-terminated string
    idAction: Integer;       // HHACT_ value
    phhWinType: PHHWinType;  // Current window type structure
  end;
  {$EXTERNALSYM tagHHNTRACK}
  HHNTRACK = tagHHNTRACK;
  {$EXTERNALSYM HHNTRACK}
  THHNTrack = tagHHNTRACK;

{$IFDEF HTMLHELP_DYNAMIC_LINK}
type
  THtmlHelpA = function (hwndCaller: HWND; pszFile: PAnsiChar; uCommand: UINT;
    dwData: DWORD): HWND; stdcall;
  THtmlHelpW = function (hwndCaller: HWND; pszFile: PWideChar; uCommand: UINT;
    dwData: DWORD): HWND; stdcall;
  THtmlHelp = THtmlHelpA;

var
  HtmlHelpA: THtmlHelpA = nil;
  HtmlHelpW: THtmlHelpW = nil;
  HtmlHelp: THtmlHelp = nil;
{$ELSE}
function HtmlHelpA(hwndCaller: HWND; pszFile: PAnsiChar; uCommand: UINT;
{$IFDEF HTMLHELP11}
  dwData: DWORD): HWND; stdcall;
{$ENDIF}
{$IFDEF HTMLHELP12}
  dwData: DWORD_PTR): HWND; stdcall;
{$ENDIF}
{$EXTERNALSYM HtmlHelpA}
function HtmlHelpW(hwndCaller: HWND; pszFile: PWideChar; uCommand: UINT;
{$IFDEF HTMLHELP11}
  dwData: DWORD): HWND; stdcall;
{$ENDIF}
{$IFDEF HTMLHELP12}
  dwData: DWORD_PTR): HWND; stdcall;
{$ENDIF}
{$EXTERNALSYM HtmlHelpW}
function HtmlHelp(hwndCaller: HWND; pszFile: PChar; uCommand: UINT;
{$IFDEF HTMLHELP11}
  dwData: DWORD): HWND; stdcall;
{$ENDIF}
{$IFDEF HTMLHELP12}
  dwData: DWORD_PTR): HWND; stdcall;
{$ENDIF}
{$EXTERNALSYM HtmlHelp}
{$ENDIF}

// Use the following for GetProcAddress to load from hhctrl.ocx

const
  ATOM_HTMLHELP_API_ANSI    = LPTSTR(DWORD(WORD(14)));
  {$EXTERNALSYM ATOM_HTMLHELP_API_ANSI}
  ATOM_HTMLHELP_API_UNICODE = LPTSTR(DWORD(WORD(15)));
  {$EXTERNALSYM ATOM_HTMLHELP_API_UNICODE}

{$IFDEF HTMLHELP12}
// Global Control Properties

const
  HH_GPROPID_SINGLETHREAD     = 1; // VARIANT_BOOL: True for single thread
  {$EXTERNALSYM HH_GPROPID_SINGLETHREAD}
  HH_GPROPID_TOOLBAR_MARGIN   = 2; // long: Provides a left/right margin around the toolbar.
  {$EXTERNALSYM HH_GPROPID_TOOLBAR_MARGIN}
  HH_GPROPID_UI_LANGUAGE      = 3; // long: LangId of the UI.
  {$EXTERNALSYM HH_GPROPID_UI_LANGUAGE}
  HH_GPROPID_CURRENT_SUBSET   = 4; // BSTR: Current subset.
  {$EXTERNALSYM HH_GPROPID_CURRENT_SUBSET}
  HH_GPROPID_CONTENT_LANGUAGE = 5; // long: LandId for desired content.
  {$EXTERNALSYM HH_GPROPID_CONTENT_LANGUAGE}

type
  HH_GPROPID = HH_GPROPID_SINGLETHREAD..HH_GPROPID_CONTENT_LANGUAGE;
  {$EXTERNALSYM HH_GPROPID}
  THHGPropID = HH_GPROPID;

// Global Property structure

  PHHGlobalProperty = ^THHGlobalProperty;
  tagHH_GLOBAL_PROPERTY = record
    id: THHGPropID;
    Dummy: Integer;                        // JEDI: Added to enforce 8-byte packing
    var_: OleVariant;
  end;
  HH_GLOBAL_PROPERTY = tagHH_GLOBAL_PROPERTY;
  THHGlobalProperty = tagHH_GLOBAL_PROPERTY;
{$ENDIF}

{$IFDEF HTMLHELP_DYNAMIC_LINK}
function HtmlHelpLoaded: Boolean;
{$IFDEF HTMLHELP_DYNAMIC_LINK_EXPLICIT}
function LoadHtmlHelp: Boolean;
function UnLoadHtmlHelp: Boolean;
{$ENDIF}
{$ENDIF}

implementation

{$IFDEF HTMLHELP_DYNAMIC_LINK}
uses
  Registry, SysUtils;

var
  HtmlHelpLib: THandle = 0;

function GetOCXPath(var Path: string): Boolean;
const
  HHPathRegKey = 'CLSID\{adb880a6-d8ff-11cf-9377-00aa003b7a11}\InprocServer32';
begin
  with TRegistry.Create do
  try
    RootKey := HKEY_CLASSES_ROOT;
    if OpenKeyReadOnly(HHPathRegKey) then Path := ReadString('');
    Result := (Path <> '') and FileExists(Path);
  finally
    Free;
  end;
end;

function HtmlHelpLoaded: Boolean;
begin
  Result := HtmlHelpLib <> 0;
end;

function UnLoadHtmlHelp: Boolean;
begin
  Result := True;
  if HtmlHelpLoaded then
  begin
    if Assigned(HtmlHelp) then HtmlHelp(0, nil, HH_CLOSE_ALL, 0);
    Result := FreeLibrary(HtmlHelpLib);
    HtmlHelpLib := 0;
    @HtmlHelpA := nil;
    @HtmlHelpW := nil;
    @HtmlHelp := nil;
  end;
end;

function LoadHtmlHelp: Boolean;
const
  ProcNameA = 'HtmlHelpA';
  ProcNameW = 'HtmlHelpW';
  ProcName = ProcNameA;
var
  HHOCXPath: string;
begin
  Result := HtmlHelpLoaded;
  if (not Result) and GetOCXPath(HHOCXPath) then
  begin
    HtmlHelpLib := LoadLibrary(PChar(HHOCXPath));
    if HtmlHelpLoaded then
    begin
      @HtmlHelpA := GetProcAddress(HtmlHelpLib, ProcNameA);
      @HtmlHelpW := GetProcAddress(HtmlHelpLib, ProcNameW);
      @HtmlHelp  := GetProcAddress(HtmlHelpLib, ProcName);
      Result := Assigned(HtmlHelpA) and Assigned(HtmlHelpW);
      if not Result then UnLoadHtmlHelp;
    end;
  end;
end;
{$ELSE}
const
  hhctrl = 'hhctrl.ocx';

function HtmlHelpA; external hhctrl Name 'HtmlHelpA';
{$EXTERNALSYM HtmlHelpA}
function HtmlHelpW; external hhctrl Name 'HtmlHelpW';
{$EXTERNALSYM HtmlHelpW}
function HtmlHelp; external hhctrl Name 'HtmlHelpA';
{$EXTERNALSYM HtmlHelp}
{$ENDIF}

{$IFDEF HTMLHELP_DYNAMIC_LINK}
initialization
{$IFNDEF HTMLHELP_DYNAMIC_LINK_EXPLICIT}
  LoadHtmlHelp;
{$ENDIF}
finalization
  UnLoadHtmlHelp;
{$ENDIF}
end.