How do I read the current and maximum scroll-position of a WebBrowser control?

I can set the scroll-position with WebBro开发者_Go百科swer.Document.Window.ScrollTo(), but how do I read the current scroll-position? Also, how do I read the total height of the document?

Background: I want to make a WebBrowser displaying logs to automatically scroll down as new messages come in, but only if it's already scrolled all the way to the bottom, so that the user can scroll up inspect older messages without interruption.

i can't give you the WinForms version directly, but i can give you the version we used from managed code.

But what i wanted to really say was that you have to be careful to know if your document is in

• Standards Mode: i.e. Internet Explorer 6 or newer
• Quirks Mode: i.e. Internet Explorer 5.5 compatible mode

The reason you want to know this is because the attribute you want to query depends if the browser is in standards or quirks mode. A document in quirks mode does not support documentElement.scrollHight (i.e. it returns zero).

                                       returns the height of...
Expression                             Quirks Mode                 Standards Mode
=====================================  ==========================  ==========================
document.body.scrollHeight             document                    body
document.documentElement.scrollHeight  (not supported)             document

You want the document height, so the way to return that is:

• Standards Mode: document.documentElement.scrollHeight (returns height of document)
• Quirks mode: document.body.scrollHeight (actually returns height of document, not body)

So i actually have two helper functions:

int WebBrowserScrollHeightQuirksMode(WebBrowser wb);

int WebBrowserScrollHeightStandardsMode(WebBrowser wb);

Which forces you to figure out if your html is in Netscape 2.0 compatible mode, and figure out which one you want to call:

function WebBrowserScrollHeightQuirksMode(const WebBrowser: TWebBrowser): Integer;
var
    doc: IHTMLDocument2;
begin
   {
       Expression                             Mode       Returns ScrollHeight of
       document.body.scrollHeight             Quirks     document
       document.body.scrollHeight             Standards  body

       document.documentElement.scrollHeight  Standards  document

       We *want* the scroll height of the document, which means we should have been
       using document.documentElement.scrollHeight

       WARNING: A document in quirks mode does not support documentElement[scrollHight]
                i.e. it returns zero
   }

   doc := (WebBrowser.Document as IHTMLDocument2);
   if not Assigned(doc) then
      Result := 0
   else if not Assigned(doc.body) then
      Result := 0
   else
      Result := doc.body.getAttribute('scrollHeight', 0);
end;

And the version when the HTML is in standards mode (i.e. Internet Explorer 6 or newer):

function WebBrowserScrollHeightStandardsmode(const WebBrowser: TWebBrowser): Integer;
var
doc: IHTMLDocument2;    //ie4, has doc.body
doc3: IHTMLDocument3;   //ie5, has doc.documentElement
begin
   //Use this for IE6 or newer, with the browser in standards mode
   Result := 0;
   {
       Expression                             Mode       Returns ScrollHeight of
       =====================================  =========  =======================
       document.body.scrollHeight             Quirks     document
       document.body.scrollHeight             Standards  body
       document.documentElement.scrollHeight  Standards  document

       We *want* the scroll height of the document, which means we should have been
       using document.documentElement.scrollHeight

       WARNING: A document in quirks mode does not support documentElement[scrollHight]
                i.e. it returns zero
   }

   doc := (WebBrowser.Document as IHTMLDocument2);
   if not Assigned(doc) then
      Exit;

   //Should use doc3.documentElement scrollHeight
   if Supports(doc, IHTMLDocument3, doc3) then //Requires Windows 95, IE5
   begin
      if Assigned(doc3.documentElement) then
      begin
         Result := VarAsInteger(doc3.documentElement.getAttribute('scrollHeight', 0));
         Exit;
      end;
   end;
end;