How can I paint the whole form on a bitmap?

Question

I want to paint the whole form including its caption bar and frame on a TBitmap object.

GetFormImage is cool, but it has two problems:

Answer 1

Here is a little function that I've used that you might find useful.

Edit: Oops I didn't fully read the question. This probably doesn't work with a hidden window, but I'm not sure anything would unless the form could draw the frame itself, but it doesn't, the OS does.

function GetScreenShot(const aWndHandle:THandle; AeroAware:boolean=true):TBitmap;
var
  wWindow: HDC;
  wRect : TRect;
  wDesktop : THandle;
begin
  Result  := TBitmap.Create;
  try
    if AeroAware then
      wDesktop := GetDesktopWindow
    else
      wDesktop := aWndHandle;

    wWindow := GetDC(wDesktop);
    try
      Result.PixelFormat := pf32bit;
      GetWindowRect(aWndHandle, wRect);
      Result.Width := wRect.Right-wRect.Left;
      Result.Height := wRect.Bottom-wRect.Top;
      if AeroAware then
        BitBlt(Result.Canvas.Handle, 0, 0, Result.Width, Result.Height, wWindow, wRect.Left, wRect.Top, SRCCOPY)
      else
        BitBlt(Result.Canvas.Handle, 0, 0, Result.Width, Result.Height, wWindow, 0, 0, SRCCOPY);
      Result.Modified := True;
    finally
      ReleaseDC(wDesktop, wWindow);
    end;
  except
    Result.Free;
    Result := nil;
  end;
end;

Answer 2

The key to accessing non-client area is GetWindowDC function, everything else is blitting as usual:

procedure TForm5.FormClick(Sender: TObject);
var
  Bitmap: TBitmap;
  DC: HDC;
  FileName: string;
begin
  Bitmap := TBitmap.Create;
  try
    Assert(HandleAllocated);
    DC := GetWindowDC(Handle);
    Win32Check(DC <> 0);

    Bitmap.SetSize(Width, Height);

    Win32Check(BitBlt(Bitmap.Canvas.Handle, 0, 0, Width, Height, DC, 0, 0, SRCCOPY));

    FileName := Name + '.' + GraphicExtension(TBitmap);
    Bitmap.SaveToFile(FileName);

    ShellExecute(HWND_DESKTOP, nil, PChar(FileName), nil, nil, SW_NORMAL);
  finally
    ReleaseDC(Handle, DC);
    Bitmap.Free;
  end;
end;

For the second case of hidden (not painted!) window - see a comment from RRUZ.

Answer 3

About capturing form image when hidden, use

AlphaBlend := true;
AlphaBlendValue := 0;

while form is shown. The user will not see the form but GetFormImage() will capture its canvas. I think this can work with "OnTheFly" suggestion too.