[Twisted-web] canvas without flash and optimization patches

[Stefano Debenedetti]

Donovan Preston wrote:
> This is very amusing. It boggles my mind, really. The reason I used XML 
> for the Canvas RPC mechanism rather than plain text was because in 
> theory an XML parser written in C should exhibit better performance 
> than a text parser written in pure actionscript. In fact, all the other 
> work I had ever done with Flash used a plain old text format, and 
> switching to XML was supposed to be an optimization.

The problem here is that you need quite a lot of non-native code to extract data from the pseudo-DOM that the XML parser returns while you need very little to make sense of an Array returned by the String.split method, which is written in C too.

So String.split() (native) + myarray[n] (non-native) is likely to be faster than XML.parseXML() (native) + myxml.childNodes[n].firstChild.attributes.etcetc (non-native)... 

An optimization rule of thumb that is more effective in Flash than in other environments is: the less code you write, the faster it is, unfortunately this often makes for poorly readable code that tends to give too much for granted.

> With a plain text format, there is the additional difficulty of 
> supporting nested structures (which is simple in XML). Some of the 
> encodings include dicts and lists.

Choosing the right format for keeping the features while not losing speed will be a cool challenge, I hope I manage to dedicate some more time to it once I get to play with Canvas a little more, for today I am just happy to know I can rely on it as it won't necessarily crash my browser, shame on the linux version of the plugin anyway, it has always been sadly behind its Win/Mac counterparts in many ways.

ciao
ste