[webkit-dev] Javascript and WebCore

Alexander Cohen naftaly at me.com
Sun Oct 25 16:30:47 PDT 2009

On Oct 25, 2009, at 7:09 PM, Maciej Stachowiak wrote:

> On Oct 25, 2009, at 2:36 PM, Alexander Cohen wrote:
>> On Oct 25, 2009, at 5:23 PM, Maciej Stachowiak wrote:
>>> On Oct 25, 2009, at 2:01 PM, Alexander Cohen wrote:
>>>> In the events of a tag, i needed to add checks to see what type  
>>>> of script was being called. A lot if not all of the time, we will  
>>>> usually find a "javascript:" in the event code so i can also look  
>>>> there for my defined scripting language and call into the right  
>>>> code.
>>> Attribute event listeners do not usually have "javascript:" in  
>>> them. Here is an example from Google's home page:
>>> <a href="http://images.google.com/imghp?hl=en&tab=wi"  
>>> onclick=gbar.qs(this) class=gb1>Images</a>
>>> Notice that the onclick value doesn't start with javascript:. You  
>>> are probably thinking of javascript: URLs in links, like this:
>>> <a href="javascript:callSomething()">
>>> You could invent a new URL scheme that runs your scripting  
>>> language instead of JavaScript, but I don't think there is  
>>> anything you can do about onclick handlers, unless you're willing  
>>> to break compatibility with existing Web content.
>> You're right. But this does give an opportunity for my scripting  
>> language to get through since executing mine as javascript will  
>> probably result in an error. I can definitely catch that and check  
>> for another language.
> I think that would be fragile, especially if polyglot or near- 
> polyglot programs are possible. Unfortunately, inline event  
> listeners were never designed with the idea of multiple scripting  
> languages in mind. Fortunately, you can add event listeners just  
> fine using code in a <script> element, so you don't lose much by not  
> supporting them for a new scripting language.

Agreed that it could be fragile. Fortunately, at least for the time  
being, i'm just working on a proof of concept and it does make the  
transition easier from javascript to another scripting language. I'm  
also learning a lot about WebCore this way which is really nice but  
not relevant to our current discussion. :)

>> Just by curiosity, would it be bad to do something like this  
>> (notice the "newscriptinglang:" in the onload ):
>> <a href="http://images.google.com/imghp?hl=en&tab=wi"  
>> onclick=newscriptinglang:gbar.qs(this) class=gb1>Images</a
> That onclick handler is a valid JavaScript program,  
> "newscriptlanglang:" is interpreted as a goto label. Whether there  
> is Web content out there accidentally doing that, I don't know.

So i would actually need to look at the event handler code scheme  
before it gets directly passed on to javascript. I could check for my  
scripting language scheme and handle it if needed. I do how see this  
could be a problem if a developer had a goto statement that was the  
same as the name of my scripting language, but the possibility of that  
is very low, for now.


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