Change User-Agent for AJAX calls from Delphi TWebBrowser

Question

I have a Delphi application that loads the Google Maps JavaScript API in an embedded web browser. The page it loads looks like this:

<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <style>
       #map {
        height: 400px;
        width: 100%;
       }
    </style>
  </head>
  <body>
    <div id="map"></div>
    <script>
      function initMap() {
        var map = new google.maps.Map(document.getElementById('map'), {});
      }
    </script>

    <script async defer
    src="https://maps.googleapis.com/maps/api/js?v=3.29&key=~APIKEY~&callback=initMap">
    </script>
  </body>
</html>

I'm displaying the page like this in a TWebBrowser:

str := StringReplace(htmlBase, '~APIKEY~', cMapsAPIKey, []);

if not Assigned(WebBrowser.Document) then
  WebBrowser.Navigate('about:blank', '1', '', '', 'User-Agent: Mozilla/5.0');

doc := WebBrowser.Document;
doc.Clear;
doc.Write(str);
doc.Close;

TWebBrowser.Navigate() will use the user agent string I've provided for the main page, but it uses this to load the scripts:

User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 10.0; WOW64; Trident/7.0; .NET4.0C; .NET4.0E; .NET CLR 2.0.50727; .NET CLR 3.0.30729; .NET CLR 3.5.30729; InfoPath.3)

Starting with 3.29, the Google Maps JavaScript API seems to be checking the browser's user agent and displaying an error message: "You are using a browser that is not supported". This isn't an issue with 3.28 or below. The browser is supported (it's using IE 11), it's just sending the wrong user agent string.

On the JavaScript end, how can I override the user agent check without disabling warnings completely? And on the Delphi end, is there a way to change the user agent for AJAX calls?

Edit: Overriding TWebBrowser.Invoke() lets me change the user agent for all HTTP requests, but it looks like navigator.userAgent isn't being changed.

Remy Lebeau · Accepted Answer · 2017-08-10T00:54:46.273

You appear to be using the VCL's TWebBrowser. Per Changing the UA (User Agent) of a TWebBrowser component, you can derive a new class from TWebBrowser to override its Invoke() method to return the desired UserAgent string when the DISPID_AMBIENT_USERAGENT property is requested. Then query the browser for its IOleControl interface and call its OnAmbientPropertyChange() method to signal to the browser that the DISPID_AMBIENT_USERAGENT property value has changed. The article has full code.

For good measure, in FMX's TWebBrowser, per Change User Agent for FireMonkey TWebBrowser, on Android you can use a helper class and RTTI trickery to access the browser's internal Java WebView object and call its WebSettings.setUserAgentString() method. Not sure about Windows, but on iOS you don't customize the user agent via the web browser itself (unless you hack the FMX framework to customize the requests it sends), you have to create a dictionary containing an item named UserAgent and register it with the global standardUserDefaults dictionary using its registerDefaults() method. How you do that in Delphi, I have no clue.

I've just tested this out. It looks like overriding `TWebBrowser` can change the user agent in the HTTP headers, but JavaScript `navigator.userAgent` still gets the old value. — David Rottenfusser, Aug 10 '17 at 16:46
I've accepted this answer since it fixes my original problem. I've submitted [another question](https://stackoverflow.com/questions/45620026/disable-google-maps-user-agent-check) about the `navigator.userAgent` issue. — David Rottenfusser, Aug 10 '17 at 17:33

score 0 · Answer 2 · answered Aug 10 '17 at 02:26

0

The problem why your Google Maps web page isn't loading fine in your TWebBrowser component is because it is working in Compatibility Mode. That is also the reason for mentioned User Agent string.

So why is this happening. Well TWebBrowser is just a wrapper for Internet Explorer browser API. And based on Microsoft decision any application that is using such API would be by default showing web pages in Compatibility mode.

You can disable this by using instructions here: https://stackoverflow.com/a/25843958/3636228

answered Aug 10 '17 at 02:26

SilverWarior

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The web page is loading fine. The first line of HTML `` disables compatibility mode for the document -- the problem is the user agent. – David Rottenfusser Aug 10 '17 at 16:19
The first line of HTML just tells browser for which browser was webpage optimized. But ultimately it is up to browser to decide in which compatibility mode will it load the web page and its active content. So unfortunately that line is not enough. – SilverWarior Aug 10 '17 at 16:24
Again, the web page is loading fine and rendering in IE 11 mode. The only problem is `navigator.userAgent` is set to the wrong value. – David Rottenfusser Aug 10 '17 at 16:52

Change User-Agent for AJAX calls from Delphi TWebBrowser

2 Answers2