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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-PRAXiShttps://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:

Code:

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)

Code:

{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

* App. Name : DelphiPlug

* Autor : Daniel Wischnewski

* 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

* 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: string; override; stdcall;

function GetAuthor: string; override; stdcall;

function GetComment: string; override; stdcall;

function GetPage: string; override; stdcall;

{$IFDEF MSWINDOWS}

function GetGlyph: HICON; override; stdcall;

{$ENDIF}

{$IFDEF LINUX}

function GetGlyph: Cardinal; override; stdcall;

{$ENDIF}

function GetStyle: TExpertStyle; override; stdcall;

function GetState: TExpertState; override; stdcall;

function GetIDString: string; override; stdcall;

function GetMenuText: string; override; stdcall;

{ Launch the Expert }

procedure Execute; override; stdcall;

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;

{ TDelphiPlug }

procedure TDelphiPlug.Execute;

begin

// en:

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

// help menu

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

Result := 'sakura (Daniel Wischnewski)';

end;

function TDelphiPlug.GetComment: string;

begin

// en:

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

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

Result := NOERROR;

end;

{$ENDIF}

{$IFDEF LINUX}

function TDelphiPlug.GetGlyph: Cardinal;

begin

// en:

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

Result := NOERROR;

end;

{$ENDIF}

function TDelphiPlug.GetIDString: string;

begin

// en:

// id of the expert

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

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

end;

function TDelphiPlug.GetName: string;

begin

// en:

// this name must be unique

Result := 'sakura_DelphiPlugSample';

end;

function TDelphiPlug.GetPage: string;

begin

// en:

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

Result := '';

end;

function TDelphiPlug.GetState: TExpertState;

begin

// en:

// returns a set of states

// possible values: esEnabled, esChecked

Result := [esEnabled];

end;

function TDelphiPlug.GetStyle: TExpertStyle;

begin

// en:

// returns the type of expert

Result := esStandard;

end;

end.

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