Как использовать CHM help в своём проекте?

Материал из DRKB


Всё, что вам надо сделать, это сохранить ниже приведенный модуль на диске и добавить его в Uses вашего проекта. После этого Вы сможете использовать CHM файлы точно так же как и обычные HLP файлы.


unit StoHtmlHelp;
////////////////////////////////////////////////////////////////
// Implementation of context sensitive HTML help (.chm) for Delphi.
//
// Version:       1.2
// Author:        Martin Stoeckli
// Homepage:      www.martinstoeckli.ch/delphi
// Copyright(c):  Martin Stoeckli 2002
//
// Restrictions:  - Works only under the Windows platform.
//                - Is written for Delphi v7, should work from v6 up.
//
// Description
// ***********
// This unit enables you to call ".chm" files from your Delphi projects.
// You can use the normal Delphi VCL framework, write your projects the
// same way, as you would using normal ".hlp" files.
//
// Installation
// ************
// Simply add this unit to your project, that's all.
//
// If your help project contains files with the extension ".html"
// instead of ".htm", then you can either pass the filename with the
// extension to Application.HelpJump(), or you can set the property
// "HtmlExt" of the global object in this unit.
//   StoHelpViewer.HtmlExt := '.html';
//
// Examples
// ********
//   // assign a helpfile, you could also select the helpfile at the
//   // options dialog "Project/Options.../Application".
//   Application.HelpFile := 'C:\MyHelp.chm';
//   ...
//   // shows the contents of the helpfile
//   Application.HelpCommand(HELP_CONTENTS, 0);
//   // or
//   Application.HelpSystem.ShowTableOfContents;
//   ...
//   // opens the context sensitive help with a numerical id.
//   // you could do the same by setting the "HelpContext"
//   // property of a component and pressing the F1 key.
//   Application.HelpContext(1000);
//   // or with a string constant
//   Application.HelpJump('welcome');
//   ...
//   // opens the help index with a keyword.
//   // you could do the same by setting the "HelpKeyword"
//   // property of a component and pressing the F1 key.
//   Application.HelpKeyword('how to do');
//

interface
uses Classes, Windows, HelpIntfs;

type
  THtmlHelpA = function(hwndCaller: HWND; pszFile: LPCSTR; uCommand: UINT; dwData: DWORD): HWND; stdcall;

  TStoHtmlHelpViewer = class(TInterfacedObject, ICustomHelpViewer,
                             IExtendedHelpViewer, IHelpSelector)
  private
    FViewerID: Integer;
    FViewerName: String;
    FHtmlHelpFunction: THtmlHelpA;
  protected
    FHHCtrlHandle: THandle;
    FHelpManager: IHelpManager;
    FHtmlExt: String;
    function  GetHelpFileName: String;
    function  IsChmFile(const FileName: String): Boolean;
    procedure InternalShutdown;
    procedure CallHtmlHelp(const HelpFile: String; uCommand: UINT; dwData: DWORD);
    // ICustomHelpViewer
    function  GetViewerName: String;
    function  UnderstandsKeyword(const HelpString: String): Integer;
    function  GetHelpStrings(const HelpString: String): TStringList;
    function  CanShowTableOfContents: Boolean;
    procedure ShowTableOfContents;
    procedure ShowHelp(const HelpString: String);
    procedure NotifyID(const ViewerID: Integer);
    procedure SoftShutDown;
    procedure ShutDown;
    // IExtendedHelpViewer
    function  UnderstandsTopic(const Topic: String): Boolean;
    procedure DisplayTopic(const Topic: String);
    function  UnderstandsContext(const ContextID: Integer;
      const HelpFileName: String): Boolean;
    procedure DisplayHelpByContext(const ContextID: Integer;
      const HelpFileName: String);
    // IHelpSelector
    function  SelectKeyword(Keywords: TStrings) : Integer;
    function  TableOfContents(Contents: TStrings): Integer;
  public
    constructor Create; virtual;
    destructor Destroy; override;
    property HtmlExt: String read FHtmlExt write FHtmlExt;
  end;

var
  StoHelpViewer: TStoHtmlHelpViewer;

implementation

uses Forms, SysUtils, WinHelpViewer;

const
  // imported from HTML Help Workshop
  HH_DISPLAY_TOPIC        = $0000;
  HH_HELP_FINDER          = $0000; // WinHelp equivalent
  HH_DISPLAY_TOC          = $0001;
  HH_DISPLAY_INDEX        = $0002;
  HH_DISPLAY_SEARCH       = $0003;
  HH_KEYWORD_LOOKUP       = $000D;
  HH_DISPLAY_TEXT_POPUP   = $000E; // display string resource id or text in a popup window
  HH_HELP_CONTEXT         = $000F; // display mapped numeric value in dwData
  HH_TP_HELP_CONTEXTMENU  = $0010; // text popup help, same as WinHelp HELP_CONTEXTMENU
  HH_TP_HELP_WM_HELP      = $0011; // text popup help, same as WinHelp HELP_WM_HELP
  HH_CLOSE_ALL            = $0012; // close all windows opened directly or indirectly by the caller
  HH_ALINK_LOOKUP         = $0013; // ALink version of HH_KEYWORD_LOOKUP
  HH_GET_LAST_ERROR       = $0014; // not currently implemented // See HHERROR.h

type
  TStoWinHelpTester = class(TInterfacedObject, IWinHelpTester)
  protected
    // IWinHelpTester
    function CanShowALink(const ALink, FileName: String): Boolean;
    function CanShowTopic(const Topic, FileName: String): Boolean;
    function CanShowContext(const Context: Integer;
                            const FileName: String): Boolean;
    function GetHelpStrings(const ALink: String): TStringList;
    function GetHelpPath : String;
    function GetDefaultHelpFile: String;
    function IsHlpFile(const FileName: String): Boolean;
  end;

////////////////////////////////////////////////////////////////
// like "Application.ExeName", but in a DLL you get the name of
// the DLL instead of the application name
function Sto_GetModuleName: String;
var
  szFileName: array[0..MAX_PATH] of Char;
begin
  FillChar(szFileName, SizeOf(szFileName), #0);
  GetModuleFileName(hInstance, szFileName, MAX_PATH);
  Result := szFileName;
end;

////////////////////////////////////////////////////////////////
{ TStoHtmlHelpViewer }
////////////////////////////////////////////////////////////////

procedure TStoHtmlHelpViewer.CallHtmlHelp(const HelpFile: String; uCommand: UINT; dwData: DWORD);
begin
  if Assigned(FHtmlHelpFunction) then
  begin
    case uCommand of
    HH_CLOSE_ALL: FHtmlHelpFunction(0, nil, uCommand, dwData); // special parameters
    HH_GET_LAST_ERROR: ; // ignore
    else
      FHtmlHelpFunction(FHelpManager.GetHandle, PChar(HelpFile), uCommand, dwData);
    end;
  end;
end;

function TStoHtmlHelpViewer.CanShowTableOfContents: Boolean;
begin
  Result := True;
end;

constructor TStoHtmlHelpViewer.Create;
begin
  inherited Create;
  FViewerName := 'StoHtmlHelp';
  FHtmlExt := '.htm';
  // load dll
  FHHCtrlHandle := LoadLibrary('HHCtrl.ocx');
  if (FHHCtrlHandle <> 0) then
    FHtmlHelpFunction := GetProcAddress(FHHCtrlHandle, 'HtmlHelpA');
end;

destructor TStoHtmlHelpViewer.Destroy;
begin
  StoHelpViewer := nil;
  // free dll
  FHtmlHelpFunction := nil;
  if (FHHCtrlHandle <> 0) then
    FreeLibrary(FHHCtrlHandle);
  inherited Destroy;
end;

procedure TStoHtmlHelpViewer.DisplayHelpByContext(const ContextID: Integer;
  const HelpFileName: String);
var
  sHelpFile: String;
begin
  sHelpFile := GetHelpFileName;
  if IsChmFile(sHelpFile) then
    CallHtmlHelp(sHelpFile, HH_HELP_CONTEXT, ContextID);
end;

procedure TStoHtmlHelpViewer.DisplayTopic(const Topic: String);
var
  sHelpFile: String;
  sTopic: String;
  sFileExt: String;
begin
  sHelpFile := GetHelpFileName;
  if IsChmFile(sHelpFile) then
  begin
    // prepare topicname as a html page
    sTopic := Topic;
    sFileExt := LowerCase(ExtractFileExt(sTopic));
    if (sFileExt <> '.htm') and (sFileExt <> '.html') then
      sTopic := sTopic + FHtmlExt;
    CallHtmlHelp(sHelpFile + '::/' + sTopic, HH_DISPLAY_TOPIC, 0);
  end;
end;

function TStoHtmlHelpViewer.GetHelpFileName: String;
var
  sPath: String;
begin
  Result := '';
  // ask for the helpfile name
  if Assigned(FHelpManager) then
    Result := FHelpManager.GetHelpFile;
  if (Result = '') then
    Result := Application.CurrentHelpFile;
  // if no path is specified, then add the application path
  // (otherwise the file won't be found if the current directory is wrong).
  if (Result <> '') then
  begin
    sPath := ExtractFilePath(Result);
    if (sPath = '') then
      Result := ExtractFilePath(Sto_GetModuleName) + Result;
  end;
end;

function TStoHtmlHelpViewer.GetHelpStrings(const HelpString: String): TStringList;
begin
  // create a tagged keyword
  Result := TStringList.Create;
  Result.Add(Format('%s: %s', [FViewerName, HelpString]));
end;

function TStoHtmlHelpViewer.GetViewerName: String;
begin
  Result := FViewerName;
end;

procedure TStoHtmlHelpViewer.InternalShutdown;
begin
  if Assigned(FHelpManager) then
  begin
    FHelpManager.Release(FViewerID);
    FHelpManager := nil;
  end;
end;

function TStoHtmlHelpViewer.IsChmFile(const FileName: String): Boolean;
var
  iPos: Integer;
  sFileExt: String;
begin
  // find extension
  iPos := LastDelimiter('.', FileName);
  if (iPos > 0) then
  begin
    sFileExt := Copy(FileName, iPos, Length(FileName));
    Result := CompareText(sFileExt, '.chm') = 0;
  end
  else
    Result := False;
end;

procedure TStoHtmlHelpViewer.NotifyID(const ViewerID: Integer);
begin
  FViewerID := ViewerID;
end;

function TStoHtmlHelpViewer.SelectKeyword(Keywords: TStrings): Integer;
var
  i: Integer;
  sViewerName: String;
begin
  Result := 0;
  i := 0;
  // find first tagged line (see GetHelpStrings)
  while (Result = 0) and (i <= Keywords.Count - 1) do
  begin
    sViewerName := Keywords.Strings[i];
    Delete(sViewerName, Pos(':', sViewerName), Length(sViewerName));
    if (FViewerName = sViewerName) then
      Result := i
    else
      Inc(i);
  end;
end;

procedure TStoHtmlHelpViewer.ShowHelp(const HelpString: String);
var
  sHelpFile: String;
  sHelpString: String;
begin
  sHelpFile := GetHelpFileName;
  if IsChmFile(sHelpFile) then
  begin
    // remove the tag if necessary (see GetHelpStrings)
    sHelpString := HelpString;
    Delete(sHelpString, 1, Pos(':', sHelpString));
    sHelpString := Trim(sHelpString);
    CallHtmlHelp(sHelpFile, HH_DISPLAY_INDEX, DWORD(Pchar(sHelpString)));
  end;
end;

procedure TStoHtmlHelpViewer.ShowTableOfContents;
var
  sHelpFile: String;
begin
  sHelpFile := GetHelpFileName;
  if IsChmFile(sHelpFile) then
    CallHtmlHelp(sHelpFile, HH_DISPLAY_TOC, 0);
end;

procedure TStoHtmlHelpViewer.ShutDown;
begin
  SoftShutDown;
  if Assigned(FHelpManager) then
    FHelpManager := nil;
end;

procedure TStoHtmlHelpViewer.SoftShutDown;
begin
  CallHtmlHelp('', HH_CLOSE_ALL, 0);
end;

function TStoHtmlHelpViewer.TableOfContents(Contents: TStrings): Integer;
begin
  // find line with viewer name
  Result := Contents.IndexOf(FViewerName);
end;

function TStoHtmlHelpViewer.UnderstandsContext(const ContextID: Integer;
  const HelpFileName: String): Boolean;
begin
  Result := IsChmFile(HelpFileName);
end;

function TStoHtmlHelpViewer.UnderstandsKeyword(const HelpString: String): Integer;
begin
  if IsChmFile(GetHelpFileName) then
    Result := 1
  else
    Result := 0;
end;

function TStoHtmlHelpViewer.UnderstandsTopic(const Topic: String): Boolean;
begin
  Result := IsChmFile(GetHelpFileName);
end;

////////////////////////////////////////////////////////////////
{ TStoWinHelpTester }
//
// delphi will call the WinHelpTester to determine, if the default
// winhelp should handle the requests.
// don't allow anything, because delphi (v7) will create an invalid
// helpfile path, calling GetHelpPath (it puts a pathdelimiter
// before the filename in "TWinHelpViewer.HelpFile").
////////////////////////////////////////////////////////////////

function TStoWinHelpTester.CanShowALink(const ALink,
  FileName: String): Boolean;
begin
  Result := False;
//  Result := IsHlpFile(FileName);
end;

function TStoWinHelpTester.CanShowContext(const Context: Integer;
  const FileName: String): Boolean;
begin
  Result := False;
//  Result := IsHlpFile(FileName);
end;

function TStoWinHelpTester.CanShowTopic(const Topic,
  FileName: String): Boolean;
begin
  Result := False;
//  Result := IsHlpFile(FileName);
end;

function TStoWinHelpTester.GetDefaultHelpFile: String;
begin
  Result := '';
end;

function TStoWinHelpTester.GetHelpPath: String;
begin
  Result := '';
end;

function TStoWinHelpTester.GetHelpStrings(
  const ALink: String): TStringList;
begin
  // as TWinHelpViewer would do it
  Result := TStringList.Create;
  Result.Add(': ' + ALink);
end;

function TStoWinHelpTester.IsHlpFile(const FileName: String): Boolean;
var
  iPos: Integer;
  sFileExt: String;
begin
  // file has extension '.hlp' ?
  iPos := LastDelimiter('.', FileName);
  if (iPos > 0) then
  begin
    sFileExt := Copy(FileName, iPos, Length(FileName));
    Result := CompareText(sFileExt, '.hlp') = 0;
  end
  else
    Result := False;
end;

initialization
  StoHelpViewer := TStoHtmlHelpViewer.Create;
  RegisterViewer(StoHelpViewer, StoHelpViewer.FHelpManager);
  Application.HelpSystem.AssignHelpSelector(StoHelpViewer);
  WinHelpTester := TStoWinHelpTester.Create;

finalization
  // do not free StoHelpViewer, because the object is referenced by the
  // interface and will be freed automatically by releasing the last reference
  if Assigned(StoHelpViewer) then
    StoHelpViewer.InternalShutdown;
end.


Source: http://www.swissdelphicenter.ch/en/tipsindex.php
ID: 04547



unit HtmlHelp;

interface

uses
  Windows, Graphics;

const
  HH_DISPLAY_TOPIC  = $0000;
  HH_DISPLAY_TOC    = $0001;
  HH_DISPLAY_INDEX  = $0002;
  HH_DISPLAY_SEARCH = $0003;
  HH_SET_WIN_TYPE   = $0004;
  HH_GET_WIN_TYPE   = $0005;
  HH_GET_WIN_HANDLE = $0006;
  HH_GET_INFO_TYPES = $0007;
  HH_SET_INFO_TYPES = $0008;
  HH_SYNC           = $0009;
  HH_ADD_NAV_UI     = $000A;
  HH_ADD_BUTTON     = $000B;
  HH_GETBROWSER_APP = $000C;
  HH_KEYWORD_LOOKUP = $000D;
  HH_DISPLAY_TEXT_POPUP = $000E;
  HH_HELP_CONTEXT   = $000F;

const
  HHWIN_PROP_ONTOP          = 2;
  HHWIN_PROP_NOTITLEBAR     = 4;
  HHWIN_PROP_NODEF_STYLES   = 8;
  HHWIN_PROP_NODEF_EXSTYLES = 16;
  HHWIN_PROP_TRI_PANE       = 32;
  HHWIN_PROP_NOTB_TEXT      = 64;
  HHWIN_PROP_POST_QUIT      = 128;
  HHWIN_PROP_AUTO_SYNC      = 256;
  HHWIN_PROP_TRACKING       = 512;
  HHWIN_PROP_TAB_SEARCH     = 1024;
  HHWIN_PROP_TAB_HISTORY    = 2048;
  HHWIN_PROP_TAB_FAVORITES  = 4096;
  HHWIN_PROP_CHANGE_TITLE   = 8192;
  HHWIN_PROP_NAV_ONLY_WIN   = 16384;
  HHWIN_PROP_NO_TOOLBAR     = 32768;

const
  HHWIN_PARAM_PROPERTIES    = 2;
  HHWIN_PARAM_STYLES        = 4;
  HHWIN_PARAM_EXSTYLES      = 8;
  HHWIN_PARAM_RECT          = 16;
  HHWIN_PARAM_NAV_WIDTH     = 32;
  HHWIN_PARAM_SHOWSTATE     = 64;
  HHWIN_PARAM_INFOTYPES     = 128;
  HHWIN_PARAM_TB_FLAGS      = 256;
  HHWIN_PARAM_EXPANSION     = 512;
  HHWIN_PARAM_TABPOS        = 1024;
  HHWIN_PARAM_TABORDER      = 2048;
  HHWIN_PARAM_HISTORY_COUNT = 4096;
  HHWIN_PARAM_CUR_TAB       = 8192;

const
  HHWIN_BUTTON_EXPAND     = 2;
  HHWIN_BUTTON_BACK       = 4;
  HHWIN_BUTTON_FORWARD    = 8;
  HHWIN_BUTTON_STOP       = 16;
  HHWIN_BUTTON_REFRESH    = 32;
  HHWIN_BUTTON_HOME       = 64;
  HHWIN_BUTTON_BROWSE_FWD = 128;
  HHWIN_BUTTON_BROWSE_BCK = 256;
  HHWIN_BUTTON_NOTES      = 512;
  HHWIN_BUTTON_CONTENTS   = 1024;
  HHWIN_BUTTON_SYNC       = 2048;
  HHWIN_BUTTON_OPTIONS    = 4096;
  HHWIN_BUTTON_PRINT      = 8192;
  HHWIN_BUTTON_INDEX      = 16384;
  HHWIN_BUTTON_SEARCH     = 32768;
  HHWIN_BUTTON_HISTORY    = 65536;
  HHWIN_BUTTON_FAVORITES  = 131072;
  HHWIN_BUTTON_JUMP1      = 262144;
  HHWIN_BUTTON_JUMP2      = 524288;
  HHWIN_BUTTON_ZOOM       = HHWIN_Button_Jump2 * 2;
  HHWIN_BUTTON_TOC_NEXT   = HHWIN_Button_Zoom * 2;
  HHWIN_BUTTON_TOC_PREV   = HHWIN_Button_Toc_Next * 2;

const
  HHWIN_DEF_Buttons = HHWIN_Button_Expand or HHWIN_Button_Back or
    HHWIN_Button_Options or HHWIN_Button_Print;

const
  IDTB_EXPAND      = 200;
  IDTB_CONTRACT    = 201;
  IDTB_STOP        = 202;
  IDTB_REFRESH     = 203;
  IDTB_BACK        = 204;
  IDTB_HOME        = 205;
  IDTB_SYNC        = 206;
  IDTB_PRINT       = 207;
  IDTB_OPTIONS     = 208;
  IDTB_FORWARD     = 209;
  IDTB_NOTES       = 210;
  IDTB_BROWSE_FWD  = 211;
  IDTB_BROWSE_BACK = 212;
  IDTB_CONTENTS    = 213;
  IDTB_INDEX       = 214;
  IDTB_SEARCH      = 215;
  IDTB_HISTORY     = 216;
  IDTB_FAVORITES   = 217;
  IDTB_JUMP1       = 218;
  IDTB_JUMP2       = 219;
  IDTB_CUSTOMIZE   = 221;
  IDTB_ZOOM        = 222;
  IDTB_TOC_NEXT    = 223;
  IDTB_TOC_PREV    = 224;

const
  HHN_First = Cardinal(-860);
  HHN_Last  = Cardinal(-879);

  HHN_NavComplete = HHN_First - 0;
  HHN_Track       = HHN_First - 1;

type
  HHN_Notify = record
    hdr: Pointer;
    pszUrl: PWideChar;
  end;

  HH_Popup = record
    cbStruct: Integer;
    hinst: THandle;
    idString: Cardinal;
    pszText: PChar;
    pt: TPoint;
    clrForeground: TColor;
    clrBackground: TColor;
    rcMargins: TRect;
    pszFont: PChar;
  end;

  HH_AKLINK = record
    cbStruct: Integer;
    fReserved: bool;
    pszKeywords: PChar;
    pszUrl: PChar;
    pszMsgText: PChar;
    pszMsgTitle: PChar;
    pszWindow: PChar;
    fIndexOnFail: bool;
  end;

type
  HHWin_NavTypes = (HHWIN_NAVTYPE_TOC,
    HHWIN_NAVTYPE_INDEX,
    HHWIN_NAVTYPE_SEARCH,
    HHWIN_NAVTYPE_HISTORY,
    HHWIN_NAVTYPE_FAVOURITES);

type
  HH_InfoType  = Longint;
  PHH_InfoType = ^ HH_InfoType;

type
  HHWin_NavTabs = (HHWIN_NavTab_Top,
    HHWIN_NavTab_Left,
    HHWIN_NavTab_Bottom);

const
  HH_Max_Tabs = 19;

type
  HH_Tabs = (HH_TAB_CONTENTS,
    HH_TAB_INDEX,
    HH_TAB_SEARCH,
    HH_TAB_HISTORY,
    HH_TAB_FAVORITES
    );

const
  HH_FTS_DEFAULT_PROXIMITY = (-1);

type
  HH_FTS_Query = record
    cbStruct: Integer;
    fUniCodeStrings: bool;
    pszSearchQuery: PChar;
    iProximity: Longint;
    fStemmedSearch: bool;
    fTitleOnly: bool;
    fExecute: bool;
    pszWindow: PChar;
  end;

type
  HH_WinType = record
    cbStruct: Integer;
    fUniCodeStrings: bool;
    pszType: PChar;
    fsValidMembers: Longint;
    fsWinProperties: Longint;
    pszCaption: PChar;
    dwStyles: Longint;
    dwExStyles: Longint;
    rcWindowPos: TRect;
    nShowState: Integer;
    hwndHelp: THandle;
    hwndCaller: THandle;
    paInfoTypes: ^ HH_InfoType;
    hwndToolbar: THandle;
    hwndNavigation: THandle;
    hwndHTML: THandle;
    iNavWidth: Integer;
    rcHTML: TRect;
    pszToc: PChar;
    pszIndex: PChar;
    pszFile: PChar;
    pszHome: PChar;
    fsToolbarFlags: Longint;
    fNotExpanded: bool;
    curNavType: Integer;
    tabPos: Integer;
    idNotify: Integer;
    TabOrder: array[0..HH_Max_Tabs + 1] of Byte;
    cHistory: Integer;
    pszJump1: PChar;
    pszJump2: PChar;
    pszUrlJump1: PChar;
    pszUrlJump2: PChar;
    rcMinSize: TRect;
  end;

  PHH_WinType = ^ HH_WinType;

type
  HHACTTYpes = (HHACT_TAB_CONTENTS,
    HHACT_TAB_INDEX,
    HHACT_TAB_SEARCH,
    HHACT_TAB_HISTORY,
    HHACT_TAB_FAVORITES,

    HHACT_EXPAND,
    HHACT_CONTRACT,
    HHACT_BACK,
    HHACT_FORWARD,
    HHACT_STOP,
    HHACT_REFRESH,
    HHACT_HOME,
    HHACT_SYNC,
    HHACT_OPTIONS,
    HHACT_PRINT,
    HHACT_HIGHLIGHT,
    HHACT_CUSTOMIZE,
    HHACT_JUMP1,
    HHACT_JUMP2,
    HHACT_ZOOM,
    HHACT_TOC_NEXT,
    HHACT_TOC_PREV,
    HHACT_NOTES,

    HHACT_LAST_ENUM
    );

type
  HHNTRACK = record
    hdr: TNMHDR;
    pszCurUrl: PWideChar;
    idAction: Integer;
    phhWinType: ^ HH_WinType;
  end;
  PHHNTRACK = ^ HHNTRACK;

  HHNNAVCOMPLETE = record
    hdr: TNMHDR;
    pszUrl: PChar;
  end;
  PHHNNAVCOMPLETE = ^ HHNNAVCOMPLETE;

type
  THtmlHelpA = function(hwndCaller: THandle; pszFile: PChar;
    uCommand: Cardinal; dwData: Longint): THandle;
  stdCall;
  THtmlHelpW = function(hwndCaller: THandle; pszFile: PChar;
    uCommand: Cardinal; dwData: Longint): THandle;
  stdCall;

function HH(hwndCaller: THandle; pszFile: PChar; uCommand: Cardinal;
  dwData: Longint): THandle;
function HtmlHelpInstalled: Boolean;

implementation

const
  ATOM_HTMLHELP_API_ANSI = #14#0;
  ATOM_HTMLHELP_API_UNICODE = #15#0;

var
  HtmlHelpA: THtmlHelpA;
  OCXHandle: THandle;

function HH;
begin
  Result := 0;
  if (Assigned(HtmlHelpA)) then
  begin
    Result := HtmlHelpA(hwndCaller, pszFile, uCommand, dwData);
  end;
end;

function HtmlHelpInstalled: Boolean;
begin
  Result := (Assigned(HtmlHelpA));
end;

initialization

  begin
    HtmlHelpA := nil;
    OCXHandle := LoadLibrary('HHCtrl.OCX');
    if (OCXHandle <> 0) then
    begin
      HtmlHelpA := GetProcAddress(OCXHandle, 'HtmlHelpA');
    end;
  end;

finalization

  begin
    if (OCXHandle <> 0) then
      FreeLibrary(OCXHandle);
  end;

end.
//-----------------------------------------------


unit Unit1;

{....}

implementation

uses
  HtmlHelp;

const
  HH_HELP_CONTEXT = $F;
  MYHELP_FILE = 'DualHelp.chm' + Chr(0);
var
  RetCode: LongInt;

  {$R *.DFM}

procedure TForm1.FormKeyUp(Sender: TObject; var Key: Word; Shift: TShiftState);
begin
  if Key = vk_f1 then
  begin
    if HtmlHelpInstalled = True then
    begin
      RetCode := HH(Form1.Handle, PChar(MYHELP_FILE), HH_HELP_CONTEXT,
        ActiveControl.HelpContext);
      Key := 0; // eat it!
    end
    else
      helpfile := 'hhtest.hlp';
  end;
end;


Source: http://www.swissdelphicenter.ch/en/tipsindex.php
ID: 04548