[whatwg] createImageData

[Maciej Stachowiak]

On Jun 9, 2008, at 8:25 PM, Jonas Sicking wrote:

> Vladimir Vukicevic wrote:
>> Sorry it took me a bit to respond here... so, ok, based on the  
>> discussion, I'd suggest:
>> - user-created ImageData-like objects should be supported, e.g.  
>> with language such as:
>
> Do note that dealing with user-created objects isn't trivial. You  
> have to be prepared for dealing with the user-created object  
> changing the whole world under you during a callback, this includes  
> things like doing any modification to the canvas object itself, but  
> also things like script navigating away and then causing a GC to  
> tear down the world around you.
>
> This is usually not very hard to deal with, as long as you are not  
> deep inside a long callstack when calling out to content. This is  
> because you have to ensure that the whole callstack is ok with the  
> world changing around it.

As an additional note: inn implementations that support getters and  
setters, any property access to a user-created object may call back  
into arbitrary JS code. Even in those that do not, a toNumber  
conversion of an arbitrary JS value may call back into arbitrary JS  
code.

Regards,
Maciej