Windows Search Engine - Delphi

The Shell supports several search utilities that allow users to locate namespace objects such as files or printers. You can create a custom search engine and make it available to users by implementing and registering a search handler.

Users have two ways to select a search engine. The first way is from the Start menu. With systems earlier than Microsoft Windows 2000, selecting the Find command on the Start menu displays a submenu of the available search engines. With Windows 2000 and later, the Start menu's Find command is renamed Search.
Users can also launch a search from Windows Explorer. On systems earlier than Windows 2000, they click the Find command on the Tools menu to display essentially the same menu as the one associated with the Start menu. However, Windows Explorer for Windows 2000 handles search engines in a very different way. Instead of handling search engines as a submenu of the Tools menu, there is now a Search button on the toolbar. Clicking this button opens the Explorer bar's Search pane

The following example shows how to implement Shell Search Handler using Borland Delphi. As any Shell Extension it must be implemented as in-process Component Object Model (COM) object. It must be assigned a globally unique identifier (GUID) and registered using regsvr32.exe

library SearchHandler;

uses
ComServ,
HandlerM in 'HandlerM.pas';

{$R *.RES}

exports
DllGetClassObject,
DllCanUnloadNow,
DllRegisterServer,
DllUnregisterServer;

begin
end.

{*****************************************************************************
Name : TSearchEngine
Author : Perevoznyk Serhiy
Description : Shell Search Handler
*****************************************************************************}

unit HandlerM;

interface

uses
Windows, ActiveX, ComObj, ShlObj, Dialogs;

type
TSearchEngine = class(TComObject, IShellExtInit, IContextMenu)
protected
{ IShellExtInit }
function IShellExtInit.Initialize = SEIInitialize; // Avoid compiler warning
function SEIInitialize(pidlFolder: PItemIDList; lpdobj: IDataObject;
hKeyProgID: HKEY): HResult; stdcall;
{ IContextMenu }
function QueryContextMenu(Menu: HMENU; indexMenu, idCmdFirst, idCmdLast,
uFlags: UINT): HResult; stdcall;
function InvokeCommand(var lpici: TCMInvokeCommandInfo): HResult; stdcall;
function GetCommandString(idCmd, uType: UINT; pwReserved: PUINT;
pszName: LPSTR; cchMax: UINT): HResult; stdcall;
end;

const
Class_SearchEngine: TGUID = '{B8091A44-1F5E-4EFE-8F26-194ACBDE4465}';

implementation

uses ComServ, SysUtils, ShellApi, Registry;

function TSearchEngine.SEIInitialize(pidlFolder: PItemIDList; lpdobj: IDataObject;
hKeyProgID: HKEY): HResult;
begin
Result := NOERROR;
end;

function TSearchEngine.QueryContextMenu(Menu: HMENU; indexMenu, idCmdFirst,
idCmdLast, uFlags: UINT): HResult;
begin
Result := 0;
end;


function TSearchEngine.InvokeCommand(var lpici: TCMInvokeCommandInfo): HResult;
begin
//enter your code here
ShowMessage('Executed');
Result := NOERROR;
end;

function TSearchEngine.GetCommandString(idCmd, uType: UINT; pwReserved: PUINT;
pszName: LPSTR; cchMax: UINT): HRESULT;
begin
if (idCmd = 0) then
begin
if (uType = GCS_HELPTEXT) then
// return help string for menu item
StrCopy(pszName, 'Find document');
Result := NOERROR;
end
else
Result := E_INVALIDARG;
end;

type
TSearchEngineFactory = class(TComObjectFactory)
public
procedure UpdateRegistry(Register: Boolean); override;
end;


procedure CreateKey(const Key, ValueName, Value: string);
var
Handle: HKey;
Status, Disposition: Integer;
begin
Status := RegCreateKeyEx(HKEY_LOCAL_MACHINE, PChar(Key), 0, '',
REG_OPTION_NON_VOLATILE, KEY_READ or KEY_WRITE, nil, Handle,
@Disposition);
if Status = 0 then
begin
RegSetValueEx(Handle, PChar(ValueName), 0, REG_SZ,
PChar(Value), Length(Value) + 1);
RegCloseKey(Handle);
end;
end;


procedure DeleteKey(const Key: string);
begin
RegDeleteKey(HKEY_LOCAL_MACHINE, PChar(Key));
end;

procedure TSearchEngineFactory.UpdateRegistry(Register: Boolean);
var
ClassID: string;
FileName: array [0..MAX_PATH] of Char;
begin
if Register then
begin
inherited UpdateRegistry(Register);
ClassID := GUIDToString(Class_SearchEngine);
GetModuleFileName(HInstance, FileName, SizeOf(FileName));
CreateKey('Software\Microsoft\Windows\CurrentVersion\Explorer\FindExtensions\Static\SearchHandler', '', ClassID);
CreateKey('Software\Microsoft\Windows\CurrentVersion\Explorer\FindExtensions\Static\SearchHandler\0', '', 'Using Delphi...');
CreateKey('Software\Microsoft\Windows\CurrentVersion\Explorer\FindExtensions\Static\SearchHandler\0\DefaultIcon', '', FileName + ',0');
end
else
begin
DeleteKey('Software\Microsoft\Windows\CurrentVersion\Explorer\FindExtensions\Static\SearchHandler\0\DefaultIcon');
DeleteKey('Software\Microsoft\Windows\CurrentVersion\Explorer\FindExtensions\Static\SearchHandler\0');
DeleteKey('Software\Microsoft\Windows\CurrentVersion\Explorer\FindExtensions\Static\SearchHandler');
inherited UpdateRegistry(Register);
end;
end;

initialization
TSearchEngineFactory.Create(ComServer, TSearchEngine, Class_SearchEngine,
'', 'Delphi Search Engine Example', ciMultiInstance,
tmApartment);
end.