How I can get information about the scrollbars of an Webbrowser control instance or the IE Webrowser?

Question

I need to get information about the scrollbars (position, size, visibility) of a Webbrowser control of an external application, I tried using the GetScrollBarInfo function from my previous question, but the function always return false, I checked this function with another applications and works fine , but not with the IE or the Webbrowser control. So how I can get information about the scrollbars of an Webbrowser control instance or the IE Webbrowser?

Answer 1

Here is how you can know whether the scrollbars are visible or not. Some error checking missed for brevity.

LPDISPATCH      lpDispatch;
lpDispatch      = m_Browser.GetDocument();

IHTMLDocument2 *doc2 = NULL;
disp->QueryInterface(IID_IHTMLDocument2,(void**)&doc2);

IHTMLElement *lpBodyElement; 
IHTMLBodyElement *lpBody; 

doc2->get_body(&lpBodyElement); 
if ( lpBodyElement )
{
lpBodyElement->QueryInterface(IID_IHTMLBodyElement,(void**)&lpBody); 
if ( lpBody )
{
    BSTR bstrText; 
            pBody->get_scroll(&bstrText);
    lpBody->Release(); 
}
lpBodyElement->Release(); 
}
doc2->Release();

Possible values for bstrText are "yes", "no", "auto" (scroll bars are shown when the page content exceeds the client area)

And here is how you can know the current scroll position:

IHTMLElement2 *pElement = NULL;
hr = pBody->QueryInterface(IID_IHTMLElement2,(void**)&pElement);
ASSERT(SUCCEEDED(hr));
ASSERT( pElement );
long scroll_pos;
pElement->get_scrollTop( &scroll_pos); 

Answer 2

You can send WM_HTML_GETOBJECT message to "Internet Explorer_Server" class window of an external application to obtain IHtmlDocument2, then using IServiceProvider you can obtain IWebBrowser2 interface.
Here is some sample code in Delphi:

uses
  ActiveX, MSHTML;

type
  TObjectFromLResult = function(LRESULT: lResult; const IID: TIID;
    wParam: wParam; out pObject): HRESULT; stdcall;

function GetIEFromHWND(WHandle: HWND; var IE: IWebbrowser2): HRESULT;
var
  hInst: HWND;
  lRes: Cardinal;
  Msg: Integer;
  pDoc: IHTMLDocument2;
  ObjectFromLresult: TObjectFromLresult;
begin
  Result := S_FALSE;
  hInst := LoadLibrary('Oleacc.dll');
  @ObjectFromLresult := GetProcAddress(hInst, 'ObjectFromLresult');
  if @ObjectFromLresult <> nil then
  try
    Msg := RegisterWindowMessage('WM_HTML_GETOBJECT');
    SendMessageTimeOut(WHandle, Msg, 0, 0, SMTO_ABORTIFHUNG, 1000, lRes);
    Result := ObjectFromLresult(lRes, IHTMLDocument2, 0, pDoc);
    if Result = S_OK then
      (pDoc.parentWindow as IServiceprovider).QueryService(
        IWebbrowserApp, IWebbrowser2, IE);
  finally
    FreeLibrary(hInst);
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  Wnd, WndChild: HWND;
  IE: IWebBrowser2;
  Document: IHtmlDocument2;
  ScrollTop, ScrollLeft: Integer;
begin
  Wnd := FindWindow('IEFrame', nil); // top level IE
  if Wnd = 0 then Exit;
  WndChild := FindWindowEX(Wnd, 0, 'Shell DocObject View', nil);
  if WndChild = 0 then Exit;
  WndChild := FindWindowEX(WndChild, 0, 'Internet Explorer_Server', nil);
  if WndChild = 0 then Exit;

  GetIEFromHWnd(WndChild, IE);
  if IE <> nil then
  begin
    ShowMessage(IE.LocationURL);
    Document := IE.Document as IHtmlDocument2;
    ScrollTop := ((Document as IHTMLDocument3).documentElement as IHTMLElement2).scrollTop;
    ScrollLeft := ((Document as IHTMLDocument3).documentElement as IHTMLElement2).scrollLeft;
    ShowMessage(Format('%d;%d', [ScrollTop, ScrollLeft]));

    // visible|hidden|scroll|auto|no-display|no-content
    ShowMessage(OleVariant(Document).documentElement.currentStyle.overflowX);
    ShowMessage(OleVariant(Document).documentElement.currentStyle.overflowY);
  end;
end;

---

Edit: when page uses <!DOCTYPE> directive to switch IE6 to strict standard-compliant mode use document.documentElement. (IHTMLDocument3) in pre-standard mode, the body represents the scrollable region, so you can retrieve the scroll position with document.body.scrollTop. In standard mode, HTML element is scrollable, so you should use document.documentElement.scrollTop.

If document.documentElement.clientWidth <> 0 use the documentElement element for properties else use the body element.
Useful properties related to scroll information are also clientHeight, scrollWidth, scrollHeight.