Project Structure

• UseDyna.dpr
• UseDynaF.pas
• UseDynaF.dfm

program UseDyna;

uses
  Forms,
  UseDynaF in 'UseDynaF.pas' {Form1};

{$R *.RES}

begin
  Application.CreateForm(TForm1, Form1);
  Application.Run;
end.

unit UseDynaF;

interface

uses
  SysUtils, Windows, Messages, Classes, Graphics, Controls,
  Forms, Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    BtnChange: TButton;
    BtnSelect: TButton;
    BtnApp: TButton;
    procedure BtnChangeClick(Sender: TObject);
    procedure BtnSelectClick(Sender: TObject);
    procedure BtnAppClick(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    hInstDLL: THandle;
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

type
  TGetColorProc = function (Col: LongInt): LongInt; stdcall;
  TShowColorProc = procedure (Col: LongInt); stdcall;

procedure TForm1.BtnChangeClick(Sender: TObject);
var
  Col: LongInt;
  GetColorProc: TGetColorProc;
  FPointer: TFarProc;
begin
  FPointer := GetProcAddress (hInstDll, 'GetColor');
  if FPointer = nil then
    raise Exception.Create ('GetColor DLL function not found');
  GetColorProc := TGetColorProc (FPointer);
  // original code
  Col := ColorToRGB (Color);
  Color := GetColorProc (Col);
end;

procedure TForm1.BtnSelectClick(Sender: TObject);
var
  Col: LongInt;
  ShowColorProc: TShowColorProc;
  FPointer: TFarProc;
begin
  FPointer := GetProcAddress (hInstDll, 'ShowColor');
  if FPointer = nil then
    raise Exception.Create ('GetColor DLL function not found');
  ShowColorProc := TShowColorProc (FPointer);
  // original code
  Col := ColorToRGB (Color);
  ShowColorProc (Col);
end;

procedure TForm1.BtnAppClick(Sender: TObject);
begin
  ShowMessage ('Application Handle: ' +
    IntToStr (Application.Handle));
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  hInstDll := SafeLoadLibrary ('FormDllD.dll');
  if hInstDll <= 0 then
    raise Exception.Create ('FormDllD library not found');
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  if hInstDLL > 0 then
    FreeLibrary (hInstDLL);
end;

end.

object Form1: TForm1
  Left = 226
  Top = 129
  Width = 193
  Height = 221
  Caption = 'Use Dyna'
  Color = clBtnFace
  Font.Charset = DEFAULT_CHARSET
  Font.Color = clBlack
  Font.Height = -11
  Font.Name = 'MS Sans Serif'
  Font.Style = []
  OldCreateOrder = True
  OnCreate = FormCreate
  OnDestroy = FormDestroy
  PixelsPerInch = 96
  TextHeight = 13
  object BtnChange: TButton
    Left = 40
    Top = 34
    Width = 105
    Height = 33
    Caption = 'Change Color'
    TabOrder = 0
    OnClick = BtnChangeClick
  end
  object BtnSelect: TButton
    Left = 40
    Top = 88
    Width = 105
    Height = 33
    Caption = 'Select Color'
    TabOrder = 1
    OnClick = BtnSelectClick
  end
  object BtnApp: TButton
    Left = 40
    Top = 136
    Width = 105
    Height = 33
    Caption = 'Application'
    TabOrder = 2
    OnClick = BtnAppClick
  end
end