Bizarreries a étudier

  THttpHeader = class(specialize TFPGMap<string, string>)
  public
    procedure Parse(const HeaderString: string);
    constructor Create;
  end;

LazWebsockets\src\wsstream.pas

  TLockedEvent = specialize TThreadedData<TNotifyEvent>;
...
    function GetOnClose: TNotifyEvent;
    procedure SetOnClose(AValue: TNotifyEvent)
...
    property OnClose: TNotifyEvent read GetOnClose write SetOnClose;
...
function TWebsocketCommunicator.GetOnClose: TNotifyEvent;
begin
  try
    Result := FOnClose.Lock^;
  finally
    FOnClose.Unlock;
  end;
end;
 
procedure TWebsocketCommunicator.SetOnClose(AValue: TNotifyEvent);
begin
  try
    FOnClose.Lock^ := AValue;
  finally
    FOnClose.Unlock;
  end;
end;
...
constructor TWebsocketCommunicator.Create(AStream: TLockedSocketStream;
  AMaskMessage: boolean; AssumeMaskedMessages: boolean);
begin
...
  FOnClose.Init(nil);
...
end;
 
destructor TWebsocketCommunicator.Destroy;
begin
...
  FOnClose.Done;
  inherited Destroy;
end;
 
procedure TWebsocketCommunicator.Close(ForceClose: boolean);
var
  OnCloseEvent: TNotifyEvent;
begin
...
  OnCloseEvent := OnClose;
  if Assigned(OnCloseEvent) then
    OnCloseEvent(Self);
...
end;

Avec…

LazWebsockets\src\wsutils.pas

{ TThreadedData }
 
  generic TThreadedData<T> = record
  public type PT = ^T;
  private
    FData: T;
    FLock: TRTLCriticalSection;
  public
    procedure Init(const AValue: T);
    procedure Done;
    function Lock: PT;
    procedure Unlock;
  end;