Getting Windows Phone 7 WebBrowser Component VerticalOffset - windows-phone-7

Question

I want to persist the user's location in the document he or she is browsing, then bring them back to that spot when they return from tombstoning or between sessions.
My first approach was to wrap the browser component in a scrollviewer, but it turns out it handles its own scrolling and the scrollviewer never changes its verticaloffset.
My guess is that the browser component must have a scrollviewer or something like it embedded in it. I need to get the verticaloffset and scroll to an offset.
Any guesses how to get there?
My next approach would be a painful mish-mash of javascript and c# to figure out where they are...

Answer 1

Because of the way the WebBrowser control is built you'll need to track scrolling in Javascript then pass the location to managed code to handle storage of that value.
On resuming you'll need to have the managed code pass the scroll position to a Javascript function to reset the scroll position.
That's the theory but I haven't looked at the funcitonality around javascript scrolling events in the WebBrowser yet. That's the only place I can see possible problems.
Would be good to hear how you get on.

Answer 2

I've accepted Matt's answer, but I want to put in some details here. I'm also going to blog about how I did it once I'm completely done.
Since the WebBrowser component is essentially a black-box, you don't have as much control as I would like. Having said that, it is possible to get and set the vertical offset.
Javascript lets you ask for the value, but different browsers use different variations on HOW to ask. For THIS case I only have one browser to worry about.
First I make a couple of simple javascript functions:
function getVerticalOffset() {
return document.body.scrollTop;
}
function setVerticalOffset(offset) {
document.body.scrollTop = offset;
}
Next I call into the WebBrowser using the InvokeScript method on the browser object.
I'll post an update here with a link to my blog when I get the full write-up done.

Answer 3

I have been writing an eBook reader and had a similar question. Code for setting a scroll position has been easy enough to find.
Code for setting vertical scroll position:
string script = string.Format("window.scrollBy(0,{0});", "put your numeric value here");
wb_view.InvokeScript("eval", script);
Google didn't help much in finding solution for getting the value of current scroll position. Lacking any knowledge in javascript it took me almost two hours to get it right.
Code for getting the vertical scroll position:
var vScroll = wb_view.InvokeScript("eval",
"var vscroll = window.pageYOffset; vscroll.toString();");