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This article introduces you to the world of Delphi Experts. Delphi Experts are DLLs, that will be loaded during the startup sequence of Delphi. This article first appeared on Delphi-PRAXiShttp://www.delphipraxis.net/viewtopic.php?t=5300 in German.

NOTE: The techniques shown in this article are valid starting with Delphi 3 or 4 and since Delphi 7 they are deprecated, however, still fully suported by the Delphi IDE.

Installation of a Delphi-IDE-Expert

Every Delphi-Expert has to be registered in the Windows-Registry. For each Delphi-Version installed on a machine, as well as for each user using the machine, the Delphi-Expert has to be registered separately.

In the Registry the Delphi-Expert has to be registered under the folowing key:

HKCU\Software\Borland\Delphi\X.0\Experts

, where the X has to be replaced by the appropriate Delphi-Version supported. It may happen that the Experts key is not installed, in such case you are required to create it.

Underneath the Experts key you have to create a string value for the Delphi-Expert. The name must be unique. The value must point to the Delphi-Expert DLL, including both complete path and file name of the Delphi-Expert. Next time Delphi starts, the Expert will be loaded automatically.

The interface of the Delphi-Expert

In order for the Delphi Expert to interact with the Delphi-IDE ist has to export a function with the name ExpertEntryPoint, using the following parameters:

function InitExpert(ToolServices: TIToolServices; RegisterProc:
  TExpertRegisterProc; var Terminate: TExpertTerminateProc): Boolean; export;
  stdcall;

The first parameter ToolServices offers all "documented" interfaces to the Delphi-IDE. The second parameter RegisterProc is used to load the expert into the Delphi-IDE. The last parameter Teminate is used to notify the Expert-DLL when it is about to be unloaded by the Delphi-IDE.

The InitExpert method returns True, if the Expert has loaded successfully, otherwise it can eiter return False or raises an exception to unload the DLL from the Delphi-IDE (see code sample for solution).

The PlugIn class TIExpert

Any Delphi-Expert must be derived from the class TIExpert, which is declared in the unit ExptIntf. This class defines some abstract methods, which must be implemented by each PlugIn: GetName, GetAuthor, GetComment, GetPage, GetGlyph (different for Windows and Linux), GetStyle, GetState, GetIDString, GetMenuText and Execute. The purpose of each method is explained in the source code below.

The simplest Delphi-Expert

This Delphi-Expert want do much good, however, it shows you the basic way of getting the job done. It will show an entry in the Help menu (default behavior). Once the user clicks the menu item the method Execute from the Expert will be called. The following points must be respected in order to get the expert working:

·The method GetState must return [esEnabled] 
·The method GetStyle must return esStandard 
·The method GetMenuText returns the text to be shown in the Help menu 
·The method Execute defines the expert action upon activation 


The Library Source Code (DelphiPlugI.dpr)

{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 *
 * App. Name : DelphiPlug
 * Autor     : Daniel Wischnewski
 * Copyright : Copyright © 2000-2003 by gate(n)etwork GmbH. All Right Reserved.
 * Urheber   : Daniel Wischnewski
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}


library
 DelphiPlug;

{ Important note about DLL memory management: ShareMem must be the
  first unit in your library's USES clause AND your project's (select
  Project-View Source) USES clause if your DLL exports any procedures or
  functions that pass strings as parameters or function results. This
  applies to all strings passed to and from your DLL--even those that
  are nested in records and classes. ShareMem is the interface unit to
  the BORLNDMM.DLL shared memory manager, which must be deployed along
  with your DLL. To avoid using BORLNDMM.DLL, pass string information
  using PChar or ShortString parameters. }


uses

  ShareMem,
  ExptIntf,
  uPlugIn in
 'uPlugIn.pas';

{$R *.res}


exports

  InitExpert name
 ExpertEntryPoint;

begin

end
.

The Unit
 Source Code (uPlugIn.pas)

{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 *
 * Unit Name : uPlugIn
 * Autor     : Daniel Wischnewski
 * Copyright : Copyright © 2000-2003 by gate(n)etwork GmbH. All Right Reserved.
 * Urheber   : Daniel Wischnewski
 *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}


unit
 uPlugIn;

interface


uses

  ToolIntf, EditIntf, ExptIntf, VirtIntf, Windows, Messages;

const

  MIdx_Main = $0001
;
  MIdx_ShowItems = $0002
;
  MIdx_RunCommand = $0003
;

type

  TDelphiPlug = class
(TIExpert)
  private

  protected

  public

    // abstract methods to be overriden

    { Expert UI strings }

    function
 GetName: stringoverridestdcall;
    function
 GetAuthor: stringoverridestdcall;
    function
 GetComment: stringoverridestdcall;
    function
 GetPage: stringoverridestdcall;
{$IFDEF MSWINDOWS}

    function
 GetGlyph: HICON; overridestdcall;
{$ENDIF}

{$IFDEF LINUX}

    function
 GetGlyph: Cardinal; overridestdcall;
{$ENDIF}

    function
 GetStyle: TExpertStyle; overridestdcall;
    function
 GetState: TExpertState; overridestdcall;
    function
 GetIDString: stringoverridestdcall;
    function
 GetMenuText: stringoverridestdcall;
    { Launch the Expert }

    procedure
 Execute; overridestdcall;
  end
;

function
 InitExpert(ToolServices: TIToolServices; RegisterProc:
  TExpertRegisterProc; var
 Terminate: TExpertTerminateProc): Boolean; export;
stdcall
;

implementation


uses

  SysUtils, ShellAPI;

function
 InitExpert(ToolServices: TIToolServices; RegisterProc:
  TExpertRegisterProc; var
 Terminate: TExpertTerminateProc): Boolean; export;
  stdcall
;
var

  DelphiPlug: TDelphiPlug;
begin

  Result := True;
  try

    // assign tools services

    ExptIntf.ToolServices := ToolServices;
    // create the Delphi-Plug

    DelphiPlug := TDelphiPlug.Create;
    // register with Delphi

    RegisterProc(DelphiPlug);
  except

    // kill assistant

    ToolServices.RaiseException(ReleaseException);
  end
;
end
;

{ TDelphiPlug }


procedure
 TDelphiPlug.Execute;
begin

  // en:

  //   Execute will be called, whenever the user clicks on the menu entry in the

  //   help menu

  // de:

  //   Execute wird aufgerufen, wenn der User auf den Eintrag im Hilfe-Menü

  //   klickt

  MessageBox(ToolServices.GetParentHandle, 'How may I help you?'
'Hmm',
    MB_ICONQUESTION + MB_OK);
end
;

function
 TDelphiPlug.GetAuthor: string;
begin

  // en:

  //   returns the name of the author of the plugin

  // de:

  //   liefert den Namen des Autoren des PlugIns zurück (wofür auch immer)

  Result := 'sakura (Daniel Wischnewski)'
;
end
;

function
 TDelphiPlug.GetComment: string;
begin

  // en:

  //   I got no idea where this comment will be displayed, ever.

  // de:

  //   Auch hier weiß ich nicht, wo das jemals angezeigt wird, aber bitte...

  Result := 'A simple Delphi-PlugIn example.'
;
end
;

{$IFDEF MSWINDOWS}


function
 TDelphiPlug.GetGlyph: HICON;
begin

  // en:

  //   an icon handle for the entry in the help menu

  // de:

  //   Ein Icon-Handle fürs Menü

  Result := NOERROR;
end
;
{$ENDIF}

{$IFDEF LINUX}


function
 TDelphiPlug.GetGlyph: Cardinal;
begin

  // en:

  //   an icon handle for the entry in the help menu

  // de:

  //   Ein Icon-Handle fürs Menü

  Result := NOERROR;
end
;
{$ENDIF}


function
 TDelphiPlug.GetIDString: string;
begin

  // en:

  //   id of the expert

  // de:

  //   ID des Experten

  Result := 'DelphiPlugSampleI'
;
end
;

function
 TDelphiPlug.GetMenuText: string;
begin

  // en:

  //   this text will be schon in the help menu. each time the menu drops down,

  //   this method will be called.

  //   NOTE:

  //     the method GetState must return esStandard, otherwise the help menu

  //     entry will not be generated and shown

  //

  // de:

  //   Text der im Hilfe Menü angezeigt wird. Diese Funktion wird jedesmal

  //   aufgerufen, wenn das Hilfemenü angezeigt wird.

  //   HINWEIS:

  //     die Methode GetState muß esStandard zurückliefern, damit dieser Eintrag

  //     im Hilfemenü automatisch generiert wird

  Result := 'You will find me in the help menu'
;
end
;

function
 TDelphiPlug.GetName: string;
begin

  // en:

  //   this name must be unique

  // de:

  //   dieser Name muss!!! einmalig sein

  Result := 'sakura_DelphiPlugSample'
;
end
;

function
 TDelphiPlug.GetPage: string;
begin

  // en:

  //   interesting to experts expanding the default dialogs of the Delphi-IDE

  // de:

  //   Ist für Experte interessant, welche Standard-Dialoge erweitern sollen

  Result := ''
;
end
;

function
 TDelphiPlug.GetState: TExpertState;
begin

  // en:

  //   returns a set of states

  //   possible values: esEnabled, esChecked

  // de:

  //   liefert ein Set von Stati zurück

  //   mögliche Werte: esEnabled, esChecked

  Result := [esEnabled];
end
;

function
 TDelphiPlug.GetStyle: TExpertStyle;
begin

  // en:

  //   returns the type of expert

  // de:

  //   liefert die Art des Experten zurück

  //   mögliche Werte: esStandard, esForm, esProject, esAddIn

  Result := esStandard;
end
;

end
.
 

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