Get IHTMLTxtRange position relative to text

Question

I need to find out the position of selected text in WebBrowser control. I can acquire IHTMLTxtRange through

        IHTMLDocument2 htmlDocument = BookReaderWeb.Document as IHTMLDocument2;
        IMarkupServices ms = (IMarkupServices) htmlDocument;
        IHTMLSelectionObject selection = htmlDocument.selection;
        if (selection == null) return;
        IHTMLTxtRange range = selection.createRange() as IHTMLTxtRange;

but I have no idea how to obtain range position relative to full text (not html). thanks.

UPDATE

---

As Noseratio suggested, I implemented the following code:

        IHTMLDocument2 htmlDocument = BookReaderWeb.Document as IHTMLDocument2;
        var str = htmlDocument.body.outerText;
        IMarkupServices ms = (IMarkupServices) htmlDocument;
        IHTMLSelectionObject selection = htmlDocument.selection;
        if (selection == null) return;
        IHTMLTxtRange range = selection.createRange() as IHTMLTxtRange;
        dynamic body = htmlDocument.body;
        var bodyRange = body.createTextRange();
        bodyRange.moveToElementText(body);
        var bodyText = bodyRange.text;
        var counter = 0;
        while (bodyRange.compareEndPoints("StartToStart", range) != 0)
        {
            bodyRange.moveStart("character", 1);
            ++counter;
        }
        MessageBox.Show(str.Substring(counter, 20));

but it doesn't give correct result. The position is a few characters misplaced forward then it should be. It happens only on large html files, it works perfectly on smaller ones. Looks like dom api interprets some kind of tags as characters maybe..?

Answer 1

A dumb method (using JavaScript notation for simplicity):

1. Create a text range for document.body:
   var bodyRange = document.body.createTextRange(); bodyRange.moveToElementText(document.body);
   Now bodyRange.text corresponds to the full text.
2. Use bodyRange.moveStart("character", 1) to move forward one char at a time, and compare its start to your selection's range start with bodyRange.compareEndPoints("StartToStart", range. When they match, you've found the position of the beginning in the full text.
3. Do bodyRange.collapse(true), this would move the range's end to the the range's start.
4. Use bodyRange.moveEnd("character", 1) to move forward one char at a time, and compare its start to your selection's range start with bodyRange.compareEndPoints("EndToEnd", range). When they match, you've found the position of the end in the full text.

You can improve this algorithm by moving one word or one sentence at a time for moveStart / moveEnd, then fine-matching by one char at a time.

Also, there's a better method, which uses the standard DOM Range and Selection API. I described it here.

Updated, try the following update to your code (untested):

var tempRange = bodyRange.duplicate();
while (bodyRange.compareEndPoints("StartToStart", range) != 0)
{
    bodyRange.moveStart("character", 1);
     tempRange.setEndPoint("EndToStart", bodyRange);
    //tempRange.EndToStart(bodyRange);
    if (String.Compare(tempRange.text, ((String)bodyText).Substring(counter)) != 0)
      ++counter;
}
MessageBox.Show(str.Substring(counter, 20));