delphi - Application locks while trying to access TWebbrowsers HTML

Question

Edit Narrowed it down to this 1 line,

HTML := wb.OleObject.Document.documentElement.innerHTML;

which consumes the time... how can that be speed up?

Using the following code my application can hang for 1-2 seconds while it tries to access the HTML of a page (Delphi XE).

function Button1Click(Sender : TObject);
begin
   wb.navigate('http://10.0.0.154/stats');
   // Use a timer to poll the page - dont wait and process app messages
   timer1.enabled := true;
end;

procedure Timer1Timer(Sender : TObject);
var
  HTML : WideString;
begin
   If GetHTML(HTML) = true then
   begin
      Timer1.enabled := false;
      { do something }
   end;
end;


function GetHTML(var HTML : WideString) : boolean;
var
  Document : IHTMLDocument2;
begin
  HTML := '';
  Result := false;

  Document := wb.DOcument as IHTMLDocument2;
  If Assigned(Document) then
  begin
    try
      HTML := wb.OleObject.Document.documentElement.innerHTML;
      Result := true;
    except
      Result := false;
    end;
  end;
end;

However I notice in my GetHTML method can take 1-2 seconds to return something and it locks UI. Looking at the AQTime with Delphi XE it says that method call is slow (1-2 seconds). It's sporatic and I wonder if it fails when the page is still mid load.

The page I am loading is an inhouse page, full of javascript and 500k big, I can't use the OnDocumentComplete because it fires before the page is even ready, even if I do a check on the ReadyState it still fires to early.

Anyone able to shed some light, if their a faster way I can access the HTML of TWebbrowser?

Answer 1

Please remember that OnDocumentComplete can fire multiple times (frames) when navigating a page.

How to properly implement OnDocumentComplete:

procedure YourForm.OnDocumentComplete(
  Sender: TObject;
  const pDisp: IDispatch;
  var URL: OleVariant);
var
  currentBrowser: IWebBrowser;
  topBrowser: IWebBrowser;
  document: OleVariant;
  windowName: string;
begin
  currentBrowser := pDisp as IWebBrowser;
  topBrowser := (Sender as TWebBrowser).DefaultInterface;
  if currentBrowser = topBrowser then
    ShowMessage('Complete document was loaded')
  else
  begin
    document := currentBrowser.Document;
    windowName := document.ParentWindow.Name;
    ShowMessage(Format('Frame "%s" was loaded', [windowName]));
  end;
end;

source:

http://www.cryer.co.uk/brian/delphi/twebbrowser/twebbrowser_events.htm#OnDocumentComplete