C++ BHO added link not working

Question

Hi,

I wrote a BHO (C++/ATL following the helloworld example at http://msdn.microsoft.com/en-us/library/bb250489%28VS.85%29.aspx), but am having problems when I add to the document (IE9).

Basically I search through the text then 'linkify' certain parts.

This all works fine - I can find the node I am interested in and so I then create a new IHTMLElement like:

    pDocument->createElement(L"A", &a); //returns OK

then I set some parameters, such as

    a->setAttribute(L"href",hrefTarget,0); //also returns OK

and finally insert it at the position I want it, etc...

    CComQIPtr<IHTMLDOMNode> adom = a;

    if(adom){parentNode->insertBefore(adom,nodeBefore,NULL); }//returns OK

The resulting html is well formed, including the link I added (so, ends up in doc as <a href="good ref" ...>expected text</a> )

The problem is that it doesn't act as a link - I just see "expected text" with no functionality.....

Any ideas? Am I doing this correctly?

(I did it already in C# using spicIE, and that worked - but I'd rather have it in C++ for speed)

Thanks

Answer 1

also, after the call to createElement(L"a", &a), I tried:

    CComQIPtr<IHTMLAnchorElement> anchor = a; //but this remains null

But I would have expected this is be good if createElement worked?

So I am guessing whatever is created, it isn't recognised as a valid anchor....

(I also tried other types just in case... img, script...... none worked in returning anything other than IHTMLElement)

Anyone done this?

Answer 2

What the hrefTarget value?

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NEU_ShieldEdge

Answer 3

I have it set as:

    VARIANT hrefTarget;
    hrefTarget.vt = VT_BSTR;
    hrefTarget.bstrVal = SysAllocString(L"javascript:void(0);");

Answer 4

Well, if anyone is interested I found what the problem was....

Where I put

    pDocument->createElement(L"A", &a);

it should have been:

    CComBSTR aTag = "A";

    pDocument->createElement(aTag,&a);

Answer 5

This is well known problem with COM marshaling. C++ compiler can't distinguish between BSTR strings and WCHAR* strings. But WCHAR* string can't be marshaled between COM calls. Because COM expects true BSTR string allocated with the SysAllocString() API and located in the system heap. Meanwhile WCHAR* is allocated statically in a stack or dynamically in a process heap. As the result, WCHAR* strings will NOT work for any COM call that makes marshaling. However, there is a chance WCHAR* strings will work for STA in-proc COM objects because marshaling is switched off by default for this scenario until you manually marshal objects (through GIT or streams).

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Best regards, Sergey