If your goal is to specify the useragent string that can be done
entirely in the API layer without modifying WebCore at all (this is
how Mac browsers built on the system WebKit specify their app name).
The changes you're requesting should not involve WebCore in any way.
If you're wanting to manipulate the DOM that is purely a matter of
having a DOM binding for Qt or just getting the js global object and
using the standard JSC APIs to manipulate it.
--Oliver
On Sep 21, 2009, at 10:58 AM, Robert Hogan wrote:
Hi there,
At the moment WebKit does not deliberately expose any of the
properties of
Javascript objects to clients. Those it does expose seem to be as
much by
luck as anything else. One example is navigator.useragent, which in
Qt's
case ultimately returns whatever the client has set in
userAgentForUrl().
The more common case is illustrated by the other properties of the
navigator object. Here is the return value for navigator.appname as
defined
in NavigatorBase.cpp:
String NavigatorBase::appName() const
{
return "Netscape";
}
I would like to make it possible for the client to control the values
returned by JS objects - this is so that my project (http://
torora.net) can
ensure that the anonymity set of torora's users is properly
preserved. For
example, Torora would always ensure that the value returned for
navigator.platform would be 'WinXP' (regardless of the user's actual
OS).
This would protect the user from a website collating information on
a user
and possibly uniquely identifying them.[1]
The only way I can think of providing this API is as follows (taking
the
navigator object as an example):
1. Copy WebCore/page/Navigator.cpp to WebCore/page/qt/
NavigatorQt.cpp and
exclude Navigator.cpp from the Qt build.
2. In NavigatorQt.cpp implement the return values by calling virtual
functions in QWebPage. Following the example of userAgentForUrl() this
would take the form of:
String NavigatorBase::appName() const
{
String appName = m_frame->loader()->appName();
if (appName.isEmpty())
return NavigatorBase::appName();
return appName;
}
which calls:
String FrameLoaderClientQt::appName()
{
if (m_webFrame) {
return m_webFrame->page()->appName();
}
return String();
}
where page()->AppName() is a virtual function in QWebPage that
returns an
empty string if it is not reimplemented by the client.
3. NavigatorQt.cpp would have to do this for all elements of the
navigator
object that it wanted to offer for client control.
The same approach would have to be used for the date, screen and
window
objects, though in the case of Torora there are other ways of ensuring
those values do not give away anything so my only actual requirement
at the
moment is to control the navigator object,
I see a couple of disadvantages to this approach:
1. Likely performance hit.
2. Customized implementations of functions in the qt/ folder of the
WebCore/page directory are for functions not implemented at all in
the base
code, rather than for replacing the ones that are.
3. It's a very cumbersome way of doing things.
A proper hooking mechanism (where clients could control all javascript
objects) for javascript would seem to require a major overhaul to
webcore/javascriptcore, and I have no idea how it would work or even
if it
would be possible.
So my questions are:
- Is the above approach acceptable for QtWebKit?
- Is there any effort already underway for a hooking mechanism for
jscore?
- Is there an alternative approach anyone can think of?
[1] Torora already does this by providing a patch to webkit when
building
from source. The patch crudely overrides existing values with a
'safe' set
of hardcoded values.
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