unit X11_Shared_Memory;

interface
uses X11_Objects, X11, SYSV, xshm, type_fixes, xlib;

type
  TSHMSegment = class(X11_Objects.TObject, ISHMSegment, X11_Objects.IObject, IInterface)
  private
    fBReadOnly : Boolean;
    fSharedMemory : SYSV.ISharedMemory; // kernel side.
    fSegmentInfo : TXShmSegmentInfo; // 
{
         ShmSeg shmseg;      /\(* resource id */
           int shmid;          /\(* kernel id */
           char *shmaddr;      /\(* address in client */
           Bool readOnly;      /\(* how the server should attach it */
}

  protected
    procedure DeleteUnderlyingObject; override;
    function GetSharedMemory : ISharedMemory;
    function GetBReadOnly : TBoolean;
  published
    constructor Attach(aDisplay : PDisplay; const aSharedMemory : ISharedMemory; aBReadOnly : TBoolean = False);
    property SharedMemory : ISharedMemory read GetSharedMemory;
    property BReadOnly : TBoolean read GetBReadOnly;
  end;
  
implementation

{   XShmQueryExtension  checks to see if the shared memory extensions are available for
          the specified display.
          
                 XShmQueryVersion returns the  version  numbers  of  the  extension  implementation.
                        Shared memory pixmaps are supported if the pixmaps argument returns true.
}

procedure TSHMSegment.DeleteUnderlyingObject;
begin
  if fSegmentInfo.shmseg <> 0 then begin // FIXME is that correct?
    CheckError(XShmDetach(Display, @fSegmentInfo)); // .shmseg));
    fSegmentInfo.shmseg := 0;
  end;
end;

function TSHMSegment.GetSharedMemory : ISharedMemory;
begin
  Result := fSharedMemory;
end;

function TSHMSegment.GetBReadOnly : TBoolean;
begin
  Result := fBReadOnly;
end;

constructor TSHMSegment.Attach(aDisplay : PDisplay; const aSharedMemory : ISharedMemory; aBReadOnly : TBoolean);
begin
  fSharedMemory := aSharedMemory;
  fSegmentInfo.shmid := aSharedMemory.ID;
  fSegmentInfo.shmaddr := aSharedMemory.Address;
  if aBReadOnly then
    fSegmentInfo.readOnly := LongInt(True)
  else
    fSegmentInfo.readOnly := LongInt(False);

  CheckError(XShmAttach(aDisplay, @fSegmentInfo));
  inherited Reuse(aDisplay, fSegmentInfo.shmseg, True);
end;

end.