WPF WebBrowser JS Errors capture

Definition of the problem: Catch all the JS errors occurred in WebBrowser used in WPF application.

Luckily DOM's window has so called "external" object and WebBrowser componenet has a "ObjectForScripting" property which is "equal" to "window.external".

There are some restrictions with permissions, f.e. you cannot set your window or application as a ObjectForScripting. Otherwise you receive Exception "The object type is not visible to COM. You need to set ComVisibleAttribute attribute to True."
So I propose to use another class to do that.

Here is the source:
1st Part of code is run only once, in the window/app constructor f.e.

ObjectForScriptingHelper ScriptHelper = new ObjectForScriptingHelper(this);
wb_browser.ObjectForScripting = ScriptHelper;

2nd Part is run on Browser's "Navigated" event

private void wb_browser_Navigated(object sender, System.Windows.Navigation.NavigationEventArgs e) {
 string DisableScriptError = @"function externalError(errorMsg, document, lineNumber) {
  window.external.onError(errorMsg, document, lineNumber);
  return true;
 }
 window.onerror = externalError;";
 HTMLDocument doc2 = wb_browser.Document as HTMLDocument;
 IHTMLScriptElement scriptErrorSuppressed = (IHTMLScriptElement)doc2.createElement("SCRIPT");
 scriptErrorSuppressed.type = "text/javascript";
 scriptErrorSuppressed.text = DisableScriptError;
 IHTMLElementCollection nodes = doc2.getElementsByTagName("head");
 foreach (IHTMLElement elem in nodes)
 {

  HTMLHeadElement head = (HTMLHeadElement)elem;
  head.appendChild((IHTMLDOMNode)scriptErrorSuppressed);
 }
}

3rd Part of script is that special class:

[PermissionSet(SecurityAction.Demand, Name = "FullTrust")]
[ComVisible(true)]
public class ObjectForScriptingHelper
{
 TestingWindow m_Window;

 public ObjectForScriptingHelper(TestingWindow w)
 {
  m_Window = w;
 }

 public void onError(Object arg1, Object arg2, Object arg3)
 {
  m_Window.onError(arg1, arg2, arg3);
 }
}

And 4th Part of code is point where you can write your code:

public void onError(Object arg1, Object arg2, Object arg3) {
 //Put your handle here
}

GL & HF


SE keywords:
How to capture script error message in a WPF WebBrowser

WPF WebBrowser screenshot

Definition of the problem: Make a screenshot of WebBrowser component inside WPF application.

I've spent half of a day googling the problem.
Found some solutions
- Using "VisualBrush" - does not work for WPF, creates black image.
- Using "FromImage" - does not work either with WPF.

Finally found this one.
Much better! But there are still "BUTS"

1. "This API was accessed with arguments from the wrong context." Did not have time to figure out, why this exception is being thrown. Something with the access permission from window to window or whatever. With other words if you get exception like that, use "Dispatcher.Invoke" part of the source-code posted below.
2. Full-Page. Some pages are longer than just one screen, so you need to make more than one screenshot to map whole page into image. There are also some DOM problems related to this task - some of the properties, like body.scrollTop just ain't being updated after you call window.scrollTo, killed some time for debugging.

Here is the source code of my final solution

browser.Dispatcher.Invoke(
 System.Windows.Threading.DispatcherPriority.Normal,
 new Action(delegate(){
  HTMLDocument htmlDoc = browser.Document as HTMLDocument;
  HTMLBodyClass body = (HTMLBodyClass)htmlDoc.body;

  var topLeftCorner = browser.PointToScreen(new System.Windows.Point(0, 0));
   
  var topLeftGdiPoint = new System.Drawing.Point((int)topLeftCorner.X, (int)topLeftCorner.Y);
  var size = new System.Drawing.Size(body.clientWidth, body.clientHeight);
  var screenShot = new Bitmap(body.scrollWidth, body.scrollHeight);
  var graphics = Graphics.FromImage(screenShot);
  var cP = new System.Drawing.Point();
  var i = 0;
  var scrollTop = 0;
  var cW = (int)browser.ActualWidth;
  var cH = (int)browser.ActualHeight;
  do
  {
   scrollTop = Math.Min(cH * i, body.scrollHeight - cH);
   htmlDoc.parentWindow.scrollTo(0, scrollTop);
   newWindow.UpdateLayout();
   Thread.Sleep(1500);
   cP.X = 0;
   cP.Y = scrollTop;
   graphics.CopyFromScreen(topLeftGdiPoint, cP, size, CopyPixelOperation.SourceCopy);
   i++;
  } while (scrollTop + cH  < body.scrollHeight);

  screenShot.Save(@"C:\temp\screens\page.png", ImageFormat.Png);
 })
);

NB: This algo only scrolls vertically (downwards). But you can easily figure out the way of screening it horizontally too.

Gl & HF