Re: Getting Javascript from the DOM (re-post)

[Johnny Stenback]

This can be done in a couple of different ways, but there's no offical 
easy-to-use API's for doing this. The way to do this while relying on as 
few frozen API's as possible would be to use XPConnect to get ahold of 
the JSObject for the window where you want to execute your code, and 
then from there you can use the JS engine API's to execute a script that 
calls the function you're interested in.

To to do this, you do however need a JSContext, and which one you want 
depends on what you're doing. If you want the code to run as if it was 
executed by the document that's loaded into the window in question, then 
you need to get the JSContext from that document, or window, rather. 
This could be done using a combination of the JS context iterator 
(JS_ContextIterator()) and XPConnect, but it gets a bit tricky and 
doesn't scale all that well, so the alternative is to use frozen 
interfaces. If you have a pointer to the window, you can QI that to 
nsIScriptGlobalObject and call GetContext() on that, and you'll get an 
nsIScriptContext. On that, you can call GetNativeContext() and you'll 
get the JSContext for that window (as a void*, so you'll need to cast it 
to a JSContext). From there, you can use the JS engine API to compile 
and execute your script. If you do end up using nsIScriptContext, you're 
already using internal interfaces (which we make no guarantees about, 
they may, and probably will, change, from version to version) you can 
use the methods in that interface to execute your script as well.

I hope this gets you started!

Tom Lee wrote:

Hi ,

I read a couple articles regarding the calling of java script functionality
from C++., and I was wondering if anybody could possible help me out .
I have  an XUL toolbar (Netscape 7.x) that calls an XPCom component ( C++).
I need to be able to call a JavaScript function that may or may not be
present within the document - from my XPCOM component. I have tried several
ways, but I cannot seem to get the JavaScript within the document. I have
done this with a plug-in for IE and it works like a charm. The way I do it
in IE is listed below. I have tried several different ways to try to get the
java script and have failed:( I would greatly appreciate some insight to
this. Am I making this too complicated? Any
help you could offer  I would greatly appreciate.
Thank you very much,



...

   CComQIPtr<IWebBrowser2> spBrowser(pDispatch);

   VARIANT_BOOL b = VARIANT_FALSE;
   spBrowser->get_TopLevelContainer(&b);
    CComPtr<IDispatch> pDisp;
    spBrowser->get_Document(&pDisp);
    CComQIPtr<IHTMLDocument2> spDoc(pDisp);

//    GetDomain(pDisp);
    CComPtr<IDispatch> pScriptDisp;
    HRESULT hr = spDoc->get_Script(&pScriptDisp);
    if(pScriptDisp)
    {
     _bstr_t btMember(JSCRIPT_FUNCTION);
     DISPID dispid = NULL;
     BSTR bstrFunction = btMember.copy();

     hr = pScriptDisp->GetIDsOfNames(IID_NULL,&bstrFunction,1,
           LOCALE_SYSTEM_DEFAULT,&dispid);
     // Check to see if function exists
     if(FAILED(hr))
      return;
     int arraySize = 0;
     DISPPARAMS dispparams;
     ZeroMemory(&dispparams, sizeof(DISPPARAMS));
     dispparams.cArgs = arraySize;
     dispparams.rgvarg = new VARIANT[dispparams.cArgs];
     for( int i = 0; i < arraySize; i++)
     {
//      CComBSTR bstr = paramArray.GetAt(arraySize - 1 - i); // back reading
//      bstr.CopyTo(&dispparams.rgvarg[i].bstrVal);
//      dispparams.rgvarg[i].vt = VT_BSTR;
     }
     dispparams.cNamedArgs = 0;
     EXCEPINFO excepInfo;
     ZeroMemory(&excepInfo, sizeof(EXCEPINFO));
        CComVariant vaResult;
     UINT nArgErr = (UINT)-1;  // initialize to invalid arg
     hr = pScriptDisp->Invoke(dispid,IID_NULL,0,
           DISPATCH_METHOD,
           &dispparams,
           &vaResult,
           &excepInfo,&nArgErr);
     delete [] dispparams.rgvarg;

     if(SUCCEEDED(hr) && SUCCEEDED(excepInfo.scode))
     {
      _bstr_t b(vaResult.bstrVal, true);