Membuat aplikasi shutdown komputer di delphi

uses ShellApi;
 ...
 ShellExecute(Handle, 'open', 'c:\Windows\system32\shutdown.exe', nil, nil, SW_SHOWNORMAL) ; 

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Reading and writing INI files

Here is an overloaded group of commands to read from or write to an INI file. The routines are overloaded based on the d parameter. s is the [GROUP], k is Left side (key), d is the default or new parameter and f is the filename to use.

function GetIni(s,k: string; d: boolean; f: string=''): boolean; overload;
var
  ini: TMemIniFile;
begin
  Result := d;
  if f = '' then
  begin
    ini := TMemIniFile.Create(lowercase(ChangeFileExt(ParamStr(0),'.ini')));
  end
  else
  begin
    if not FileExists(f) then Exit;
    ini := TMemIniFile.Create(f);
  end;
  if ini.ReadString(s,k,'') = '' then
  begin
    ini.WriteBool(s,k,d);
    ini.UpdateFile;
  end;
  Result := ini.ReadBool(s,k,d);
  FreeAndNil(ini);
end;

function SetIni(s,k: string; d: boolean; f: string=''): boolean; overload;
var
  ini: TMemIniFile;
begin
  Result := d;
  if f = '' then
  begin
    ini := TMemIniFile.Create(lowercase(ChangeFileExt(ParamStr(0),'.ini')));
  end
  else
  begin
    if not FileExists(f) then Exit;
    ini := TMemIniFile.Create(f);
  end;
  ini.WriteBool(s,k,d);
  ini.UpdateFile;
  Result := ini.ReadBool(s,k,d);
  FreeAndNil(ini);
end;

function GetIni(s,k: string; d: integer; f: string=''): integer; overload;
var
  ini: TMemIniFile;
begin
  Result := d;
  if f = '' then
  begin
    ini := TMemIniFile.Create(lowercase(ChangeFileExt(ParamStr(0),'.ini')));
  end
  else
  begin
    if not FileExists(f) then Exit;
    ini := TMemIniFile.Create(f);
  end;
  if ini.ReadString(s,k,'') = '' then
  begin
    ini.WriteInteger(s,k,d);
    ini.UpdateFile;
  end;
  Result := ini.ReadInteger(s,k,d);
  FreeAndNil(ini);
end;

function SetIni(s,k: string; d:integer; f: string=''): integer; overload;
var
  ini: TMemIniFile;
begin
  Result := d;
  if f = '' then
  begin
    ini := TMemIniFile.Create(lowercase(ChangeFileExt(ParamStr(0),'.ini')));
  end
  else
  begin
    if not FileExists(f) then Exit;
    ini := TMemIniFile.Create(f);
  end;
  ini.WriteInteger(s,k,d);
  ini.UpdateFile;
  Result := ini.ReadInteger(s,k,d);
  FreeAndNil(ini);
end;

function GetIni(s,k: string; d: string; f: string=''): string; overload;
var
  ini: TMemIniFile;
begin
  Result := d;
  if f = '' then
  begin
    ini := TMemIniFile.Create(lowercase(ChangeFileExt(ParamStr(0),'.ini')));
  end
  else
  begin
    if not FileExists(f) then Exit;
    ini := TMemIniFile.Create(f);
  end;
  if ini.ReadString(s,k,'') = '' then
  begin
    ini.WriteString(s,k,d);
    ini.UpdateFile;
  end;
  Result := ini.ReadString(s,k,d);
  FreeAndNil(ini);
end;

function SetIni(s,k: string; d: string; f: string=''): string; overload;
var
  ini: TMemIniFile;
begin
  Result := d;
  if f = '' then
  begin
    ini := TMemIniFile.Create(lowercase(ChangeFileExt(ParamStr(0),'.ini')));
  end
  else
  begin
    if not FileExists(f) then Exit;
    ini := TMemIniFile.Create(f);
  end;
  ini.WriteString(s,k,d);
  ini.UpdateFile;
  Result := ini.ReadString(s,k,d);
  FreeAndNil(ini);
end;

Source : http://www.delphidabbler.com/tips/59 

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Programatically log users off

You may be thinking how can I use this procedure. Well I used it in a program where I could send commands to a remote machine.

procedure LogOff;
begin
  ExitWindowsEx(EWX_LOGOFF, 0);
end;

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Prevent system sleep

Windows detects activities such as keyboard or mouse input – after a long idle time the system might go to sleep mode and/or power off the display device.
Here's a unit you can use to prevent the system going to sleep during critical operations.

unit SystemCriticalU;

interface

uses
  Windows;

type
  TSystemCritical = class
  private
    FIsCritical: Boolean;
    procedure SetIsCritical(const Value: Boolean) ;
  protected
    procedure UpdateCritical(Value: Boolean) ; virtual;
  public
    constructor Create;
    property IsCritical: Boolean read FIsCritical write SetIsCritical;
  end;

var
  SystemCritical: TSystemCritical;

implementation

{ TSystemCritical }
// REF: http://msdn.microsoft.com/en-us/library/aa373208.aspx
type
  EXECUTION_STATE = DWORD;
  
const
  ES_SYSTEM_REQUIRED = $00000001;
  ES_DISPLAY_REQUIRED = $00000002;
  ES_USER_PRESENT = $00000004;
  ES_AWAYMODE_REQUIRED = $00000040;
  ES_CONTINUOUS = $80000000;
  
  KernelDLL = 'kernel32.dll';

{
  SetThreadExecutionState Function
  Enables an application to inform the system that it is in use,
  thereby preventing the system from entering sleep or turning off the
  display while the application is running.
}
procedure SetThreadExecutionState(ESFlags: EXECUTION_STATE);
  stdcall; external kernel32 name 'SetThreadExecutionState';

constructor TSystemCritical.Create;
begin
  inherited;
  FIsCritical := False;
end;

procedure TSystemCritical.SetIsCritical(const Value: Boolean) ;
begin
  if FIsCritical = Value then
    Exit;
  FIsCritical := Value;
  UpdateCritical(FIsCritical);
end;

procedure TSystemCritical.UpdateCritical(Value: Boolean) ;
begin
  if Value then
    // Prevent the sleep idle time-out and Power off.
    SetThreadExecutionState(ES_SYSTEM_REQUIRED or ES_CONTINUOUS)
  else
    // Clear EXECUTION_STATE flags to disable away mode and allow the
    // system to idle to sleep normally.
    SetThreadExecutionState(ES_CONTINUOUS);
end;

initialization

SystemCritical := TSystemCritical.Create;

finalization

SystemCritical.IsCritical := False;
SystemCritical.Free;

end.

Here's one usage example:

SystemCritical.IsCritical = true;
try
  // do critical operation here
  // without going in to sleep or turning off the display
finally
  SystemCritical.IsCritical = false;
end;

Source : http://www.delphidabbler.com/tips/127 

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How to turn numlock on by code

This function may come in especially handy when creating billing/financial applications where the keypad is a must. What it does is when called turns the NumLock status to "on".

uses
  Windows;
...
procedure SetNumLockOn;
var
  KeyState: TKeyBoardState;
begin
  GetKeyboardState(KeyState);
  if GetKeyState(VK_NUMLOCK) = 0 then begin
    KeyState[VK_NUMLOCK] := 1;
    SetKeyboardState(KeyState);
  end;
end;

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How to register a global hotkey

Global hotkeys are very handy when your application should be accessible at all time. For instance, you are browsing the Web and suddenly want to e-mail your friend. The most convenient way to do so would be to press a shortcut and the e-mail client would popup with a "new message" window no matter what program you are using at the time. This can be done with global shortcuts. They are system-wide no matter if the program you are using uses the same shortcut. A global shortcut is more important.
Here's the code to register and unregister a global shortcut.

uses
  Messages, Windows;
...
  // Your main form's class
  protected
    procedure WMHotKey(var Message: TMessage); message WM_HOTKEY;
...
implementation
...
procedure TMainForm.WMHotKey(var Message: TMessage);
begin
  // This example brings the application up front. Put your code here
  Application.BringToFront;
end;

Example of use:

RegisterHotKey(Handle, 100000 { Any unused number}, MOD_CONTROL, VK_F7);
// When closing program
UnregisterHotKey(Handle, 100000);

Source : http://www.delphidabbler.com/tips/16 

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Auto-resizing and centring forms on screen

Calling this procedure from the form's OnActivate event will resize the form in proportion to the screen resolution – I do my programming on resolution 1280×768 hence the constants – once the form height and width has been calculated it can then be centred.
Note – form should be set to autoresize and AutoScroll := False at least while being re-calculated. Also the font size for the form should be (probably) 12 for the font to be resized downwards for 800×600 – all controls should be set to ParentFont := True so they will resize.
While this works exactly for the old screen resolutions which were all more or less in proportion there is nothing which will resize screens properly for the newer stretched screens, eg. for 1280×960 and 1280×1024. The min ratio calculated is scrx / screenx = 1 so the form stays with original measurements.

uses
  math,windows;

const
  screenx = 1280;
  screeny = 768;

procedure tform1.autosizeall  ;
var 
  scrx,scry, k:integer ;
  ratio:double;
begin
  scrx:= GetSystemMetrics(SM_CXSCREEN); {finds screen resolution x value}
  scry:= (GetSystemMetrics(SM_CYSCREEN)); {finds screen resolution y value}

  ratio:=min(scrx/screenx,scry/screeny);
  {takes the smaller ratio and makes sure you dont make the window
  too big for the screen}

  scaleby(trunc(ratio*100),100);
  {scales all controls and attempts to place them in the correct position}

  {to centre the form on the screen}
  form1.Left:=centreleft(form1.width);
  form1.Top:=centretop(form1.Height) ;

end;

This code refers to two functions: centreleft and centretop. These are defined as follows:

function centreleft(fw:integer):integer;
  {calculates the form.left}
var
  smcx:integer;
begin
  smcx:=GetSystemMetrics(SM_CXSCREEN);
  centreleft:=(smcx-fw) div 2;
end;

function centretop(fh:integer):integer;
  {calculates the form.top}
var
  smcy:integer;
begin
  smcy:=GetSystemMetrics(SM_CYSCREEN);
  centtop:=(smcy-fh) div 2;
end;

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