How to detect navigation in TWebBrowser as opposed to clicking URLs?

Question

I'm using a TWebBrowser to display some HTML content (locally). The application is split in half, the top half has 5 tabs and the bottom half is the web browser. The contents of the browser change often, for example when changing to a different tab.

The content which is shown includes URLs which I need to prevent and stop every click. I'm trying to use the event OnBeforeNavigate2 which does detect every link clicked, but also detects when I programatically call Navigate. So, it winds up never navigating anywhere.

I tried wrapping the Navigate call so I always call something like...

procedure TForm1.Nav(const S: String);
begin
  FLoading:= True;
  try
    Web.Navigate(S);
    Sleep(50);
  finally
    FLoading:= False;
  end;
end;

(Sleep was just to try and give it a split second to wait)

And then capturing the call...

procedure TForm1.WebBeforeNavigate2(ASender: TObject; const pDisp: IDispatch;
  const URL, Flags, TargetFrameName, PostData, Headers: OleVariant;
  var Cancel: WordBool);
begin
  if not FLoading then
    Cancel:= True;
end;

No luck trying this trick. How can I detect when the page or user navigates but not when the browser is instructed to navigate?

Although TLama answered this quite nicely, I thought I'd point out my next solution would have been sloppy: whenever I call `TWebBrowser.Navigate()` include a dummy query string such as `&bypass=Y` and do a search for that query parameter in the `OnBeforeNavigate2` event. — Jerry Dodge, Jul 30 '13 at 15:07

score 4 · Accepted Answer · edited May 23 '17 at 11:49

Please note that the following is undocumented. Some people say and it works for me (on Windows 7 64-bit, with Internet Explorer 10) to check for a magical constant of the Flags parameter. If the Flags parameter of the OnBeforeNavigate2 event equals to 64, it was the user, who navigated through the link. If the Flags parameter equals to 0, it was the IWebBrowser2::Navigate method, who invoked the navigation. In code it would be:

procedure TForm1.WebBrowser1BeforeNavigate2(ASender: TObject;
  const pDisp: IDispatch; const URL, Flags, TargetFrameName, PostData,
  Headers: OleVariant; var Cancel: WordBool);
begin
  if (Flags and navHyperlink) = navHyperlink then
    ShowMessage('User clicked a link...')
  else
    ShowMessage('IWebBrowser2::Navigate has been invoked...');
end;

I wouldn't be much surprised, if that is just unintentionally undocumented flag value because that part of the MSDN is horrible.

It makes me feel like it was the [`navHyperlink`](http://msdn.microsoft.com/en-us/library/dd565688(v=vs.85).aspx) flag value passed from the navigation event... — TLama, Jul 30 '13 at 13:49

MohsenB · Answer 2 · 2022-11-10T09:20:29.937

I used this way to get full URL plus hash tags:

uses Winapi.ShellAPI, UnitFaktorMain, MsHtml;

procedure TfrmIntro.wb1NewWindow3(ASender: TObject; var ppDisp: IDispatch; var Cancel: WordBool; dwFlags: Cardinal; const bstrUrlContext, bstrUrl: WideString);
var
  vAdr     :string;
begin
  Cancel:= True;
  try
    vAdr := ((TWebBrowser(ASender).Document as IHTMLDocument2).ActiveElement as IHTMLElement).GetAttribute('href', 0);
  except
    vAdr:= bstrUrl;
  end;
  ShellExecute(Handle,
               'open',
               PWideChar(vAdr),
               nil,
               nil,
               SW_SHOW);
end;

procedure TForm1.wb2BeforeNavigate2(ASender: TObject; const pDisp: IDispatch; const URL, Flags, TargetFrameName, PostData, Headers: OleVariant; var Cancel: WordBool);
begin
  if (Flags and navHyperlink) = navHyperlink then begin
    Cancel:= True;
    ShellExecute(Handle,
               'open',
               PWideChar(VarToStr(URL)),
               nil,
               nil,
               SW_SHOW);
  end;
end;

How to detect navigation in TWebBrowser as opposed to clicking URLs?

2 Answers2