//
// The graphics engine GLScene
//

unit GLS.ScreenSaver;

(* Component for making screen-savers an easy task *)

interface

{$I Stage.Defines.inc}

uses
  Winapi.Windows,
  Winapi.Messages,
  System.Classes,
  System.SysUtils,
  System.Win.Registry,
  VCL.Dialogs,
  VCL.Controls,
  VCL.Forms,
  VCL.Extctrls;

type

  (* Options d'automatisation du screen-saver.
    ssoAutoAdjustFormProperties : all relevant properties of main form
    will be auto-adjusted (form style, border style, form size and for
    preview, ParentWindow).
    ssoAutoHookKeyboardEvents : hooks to main form's OnKeyPress and closes
    screen saver when a key is pressed (form's KeyPreview is also set to True)
    ssoAutoHookMouseEvents : hooks to main form's OnMouseMove and closes
    screen saver when mouse is moved (you mays have to handle other mouse
    move events manually if you have placed components on the form)
    ssoEnhancedMouseMoveDetection : gets the mouse position every half-second
    and closes the saver if position changed (uses GetCursorPos and a TTimer) *)
  TScreenSaverOption = (ssoAutoAdjustFormProperties, ssoAutoHookKeyboardEvents,
    ssoAutoHookMouseEvents, ssoEnhancedMouseMoveDetection);
  TScreenSaverOptions = set of TScreenSaverOption;

const
  cDefaultScreenSaverOptions = [ssoAutoAdjustFormProperties,
    ssoAutoHookKeyboardEvents, ssoEnhancedMouseMoveDetection];

type

  (* This event is fired when screen saver should start in preview mode.
    The passed hwnd is that of the small preview window in Windows Display
    Properties (or any other screen-saver previewing utility, so don't
    assume width/height is constant/universal or whatever). *)
  TScreenSaverPreviewEvent = procedure(Sender: TObject; previewHwnd: HWND)
    of object;

  (* Drop this component on your main form to make it a screensaver.
    You'll also need to change the extension from ".exe" to ".scr" (in the
    project options / application tab).
    How this component works :
    At design-time, the only event you may want to hook is
    OnPropertiesRequested (to diplay your screen-saver's config dialog,
    if you don't have one, at least fill in the AboutString property
    and it will be used in a ShowMessage)
    At run-time, once its props are loaded, this component will parse the
    command line and trigger relevant events
    Basicly, you only need to care about drawing in your main form's
    client area (in a resolution/size independant way if possible)
    There is no real difference between execution and preview modes, except
    for the events fired... and the size of the form :). *)
  TGLScreenSaver = class(TComponent)
  private
    mouseEventsToIgnore: Integer;
    FHonourWindowsPassword: Boolean;
    FOptions: TScreenSaverOptions;
    FOnPropertiesRequested: TNotifyEvent;
    FOnExecute: TNotifyEvent;
    FOnPreview: TScreenSaverPreviewEvent;
    FOnCloseQuery: TCloseQueryEvent;
    FAboutString: String;
    FInPreviewMode: Boolean;
    mouseTimer: TTimer; // alocated only if necessary
    lastMousePosition: TPoint;
    FMutex: THandle;
  protected
    procedure Loaded; override;
    procedure FormMouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
    procedure FormKeyPress(Sender: TObject; var Key: Char);
    procedure OnMouseTimer(Sender: TObject);
    procedure ConfigureSaver;
    procedure PreviewSaver;
    procedure ExecuteSaver;
  public
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;
    (* Invokes the standard Windows dialog to set the password.
      May be invoked from your Properties/Configuration dialog. *)
    procedure SetPassword;
    (* Properly handles request to close the main window.
      Returns True if the Close request wasn't canceled (by event or
      password fail) and will actually happen.
      Use this if you implemented specific screen-saver exiting in your
      main form.
      It first triggers the OnCloseQuery, where the close request can be
      canceled, if this passed, the password is checked if there is any,
      then sends a WM_CLOSE to the saver windows. *)
    function CloseSaver: Boolean;
    (* True if the screen-save is in preview mode.
      Valid only when the TScreenSaver has completed loading. *)
    property InPreviewMode: Boolean read FInPreviewMode;
  published
    property Options: TScreenSaverOptions read FOptions write FOptions
      default cDefaultScreenSaverOptions;
    (* If True, windows screen-saver password is checked before closing.
      You may be wanting to set this prop to false if you're using your
      own password scheme or do not want any password to be set. *)
    property HonourWindowsPassword: Boolean read FHonourWindowsPassword
      write FHonourWindowsPassword default True;
    { This string is displayed if OnPropertiesRequested is not used.
      You may use it as a quick "AboutBox". }
    property AboutString: String read FAboutString write FAboutString;
    (* Display the properties dialog when this event is triggered.
      This event may be called before Delphi's form auto-creation is complete,
      and should not rely on auto-created dialogs/forms but create what
      needs be. *)
    property OnPropertiesRequested: TNotifyEvent read FOnPropertiesRequested
      write FOnPropertiesRequested;
    // Fired when the saver should start executing, after form props are adjusted.
    property OnExecute: TNotifyEvent read FOnExecute write FOnExecute;
    // Fired when preview is requested, after form props are adjusted.
    property OnPreview: TScreenSaverPreviewEvent read FOnPreview
      write FOnPreview;
    (* Fired when screen-saver execution should close.
      It is invoked before querying for password (if there is a password). *)
    property OnCloseQuery: TCloseQueryEvent read FOnCloseQuery
      write FOnCloseQuery;
  end;

  (* Invokes the standard Windows dialog to set the password.
    May be invoked from your Properties/Configuration dialog. *)
procedure SetScreenSaverPassword;

// ---------------------------------------------------------------------
implementation
// ---------------------------------------------------------------------

// Returns system path and makes sure there is a trailing '\'.
function GetSystemDirectory: String;
var
  newLength: Integer;
begin
  SetLength(Result, MAX_PATH);
  newLength := Winapi.Windows.GetSystemDirectory(PChar(Result), MAX_PATH);
  SetLength(Result, newLength);
  if Copy(Result, newLength, 1) <> '\' then
    Result := Result + '\';
end;

procedure SetScreenSaverPassword;
type
  TSetPwdFunc = function(a: PAnsiChar; ParentHandle: THandle; b, c: Integer)
    : Integer; stdcall;
var
  mprDll: THandle;
  p: TSetPwdFunc;
begin
  mprDll := LoadLibrary(PChar(GetSystemDirectory + 'mpr.dll'));
  if mprDll <> 0 then
  begin
    p := GetProcAddress(mprDll, 'PwdChangePasswordA');
    if Assigned(p) then
      p('SCRSAVE', StrToIntDef(ParamStr(2), 0), 0, 0);
    FreeLibrary(mprDll);
  end;
end;


// ------------------
// ------------------ TScreenSaver ------------------
// ------------------

constructor TGLScreenSaver.Create(AOwner: TComponent);
begin
  inherited;
  mouseEventsToIgnore := 5;
  FOptions := cDefaultScreenSaverOptions;
  FHonourWindowsPassword := True;
  FMutex := 0;
end;

destructor TGLScreenSaver.Destroy;
begin
  // mouseTimer is owned, it'll be automatically destroyed if created
  CloseHandle(FMutex);
  inherited;
end;

procedure TGLScreenSaver.Loaded;
var
  param: String;
begin
  inherited;
  if not(csDesigning in ComponentState) then
  begin
    // Read the command line parameters to determine the saver mode
    if ParamCount > 0 then
    begin
      // Ignore the parameter's leading '-' or '/'
      param := UpperCase(Copy(ParamStr(1), 2, 1));
      if param = 'C' then
        ConfigureSaver
      else if ParamCount > 1 then
        if param = 'A' then
        begin
          SetPassword;
          Application.Terminate;
        end
        else if param = 'P' then
          PreviewSaver
        else
          ExecuteSaver
      else
        ExecuteSaver;
    end
    else
      ConfigureSaver;
  end;
end;

procedure TGLScreenSaver.ConfigureSaver;
begin
  if Assigned(FOnPropertiesRequested) then
  begin
    OnPropertiesRequested(Self);
    Application.Terminate;
  end
  else if FAboutString <> '' then
    ShowMessage(FAboutString);
end;

procedure TGLScreenSaver.SetPassword;
begin
  SetScreenSaverPassword;
end;

procedure TGLScreenSaver.PreviewSaver;
var
  frm: TForm;
  previewHwnd: HWND;
  previewRect: TRect;
begin
  FInPreviewMode := True;
  previewHwnd := StrToIntDef(ParamStr(2), 0);
  if ssoAutoAdjustFormProperties in FOptions then
  begin
    frm := (Owner as TForm);
    if Assigned(frm) then
    begin
      GetWindowRect(previewHwnd, previewRect);
      with previewRect do
        frm.SetBounds(0, 0, Right - Left, Bottom - Top);
      frm.BorderStyle := bsNone;
      frm.ParentWindow := previewHwnd;
      frm.Cursor := crNone;
      frm.Visible := False;
    end;
  end;
  if Assigned(FOnPreview) then
    FOnPreview(Self, previewHwnd);
end;

procedure TGLScreenSaver.ExecuteSaver;
var
  frm: TForm;
begin
  FMutex := CreateMutex(nil, True, 'GLScene::ScreenSaver');
  if (FMutex <> 0) and (GetLastError = 0) then
  begin
    frm := (Owner as TForm);
    if Assigned(frm) then
    begin
      if ssoAutoAdjustFormProperties in FOptions then
      begin
        frm.FormStyle := fsStayOnTop;
        frm.WindowState := wsMaximized;
        frm.BorderStyle := bsNone;
      end;
      if ssoAutoHookKeyboardEvents in FOptions then
      begin
        frm.OnKeyPress := FormKeyPress;
        frm.KeyPreview := True;
      end;
      if ssoAutoHookMouseEvents in FOptions then
        frm.OnMouseMove := FormMouseMove;
      if ssoEnhancedMouseMoveDetection in FOptions then
      begin
        mouseTimer := TTimer.Create(Self);
        mouseTimer.Interval := 500;
        mouseTimer.OnTimer := OnMouseTimer;
        mouseTimer.Enabled := True;
        OnMouseTimer(Self);
      end;
    end;
    if Assigned(FOnExecute) then
      FOnExecute(Self);
    ShowCursor(False);
  end
  else
    Application.Terminate;
end;

function TGLScreenSaver.CloseSaver: Boolean;
type
  TPwdProc = function(Parent: THandle): Boolean; stdcall;
const
  cScreenSaveUsePassword = 'ScreenSaveUsePassword';
var
  reg: TRegistry;
  p: TPwdProc;
  pwdCpl: THandle;
begin
  Result := True;
  if Assigned(FOnCloseQuery) then
  begin
    FOnCloseQuery(Self, Result);
    if not Result then
      Exit;
  end;
  // Try to close the saver, but check for a password first!
  // Check the registry to see if we should ask for a password.
  reg := TRegistry.Create;
  try
    reg.RootKey := HKEY_CURRENT_USER;
    if reg.OpenKey('Control Panel\Desktop', False) then
    begin
      if reg.ValueExists(cScreenSaveUsePassword) then
        if reg.ReadInteger(cScreenSaveUsePassword) <> 0 then
        begin
          // We need to ask for the password!
          // The Passwords control panel exports a routine that we can use: VerifyScreenSavePwd()
          pwdCpl := LoadLibrary(PChar(GetSystemDirectory + 'password.cpl'));
          if pwdCpl <> 0 then
          begin
            p := GetProcAddress(pwdCpl, 'VerifyScreenSavePwd');
            Result := p((Owner as TForm).Handle);
            FreeLibrary(pwdCpl);
          end;
        end;
    end;
  finally
    reg.Free;
  end;
  if Result then
  begin
    ShowCursor(True);
    SendMessage((Owner as TForm).Handle, WM_CLOSE, 0, 0);
  end;
end;

procedure TGLScreenSaver.FormMouseMove(Sender: TObject; Shift: TShiftState;
  X, Y: Integer);
begin
  if mouseEventsToIgnore <= 0 then
    CloseSaver
  else
    Dec(mouseEventsToIgnore);
end;

procedure TGLScreenSaver.FormKeyPress(Sender: TObject; var Key: Char);
begin
  CloseSaver;
end;

procedure TGLScreenSaver.OnMouseTimer(Sender: TObject);
var
  mousePos: TPoint;
begin
  GetCursorPos(mousePos);
  if Sender <> Self then
    if (mousePos.X <> lastMousePosition.X) or (mousePos.Y <> lastMousePosition.Y)
    then
      if CloseSaver then
        mouseTimer.Enabled := False;
  lastMousePosition := mousePos;
end;

initialization

RegisterClasses([TGLScreenSaver]);

end.