Once more with feeling.... On Tue, Aug 12, 2008 at 7:14 PM, Louis Ryan <[EMAIL PROTECTED]> wrote:
> Can we prove this out incrementally bottom-up. In general I think using DOM > is the right thing to do from a rewriting standpoint. So here's how I > propose we proceed > > 1. If the Caja dom is a little awkward wrap it, if not lets just use it as > is. We can always resolve this later > 2. Change the existing content rewriters to use the DOM instead of a lexer, > should be pretty easy. Maybe add some fancier rewriting like moving CSS into > HEAD > 3. Do some perf testing, look into memory overhead of dom transformation > etc. > 4. Alter GadgetSpec's to retain the dom when they are cached > 5. Alter the gadget rendering phase to serialize the content of the dom to > output > 6. Annotate the dom at parse time to make render time user-pref > substituions faster, this should be easy enough too... > > This should be enough to prove out the pipeline end-to-end and identify any > major perf niggles. Once this is done we can look into how to inject a > rewriter pipeline into the parsing phase and the rendering phase. > > -Louis > > > > > On Tue, Aug 12, 2008 at 5:57 PM, John Hjelmstad <[EMAIL PROTECTED]> wrote: > >> Re-responding in order to apply the last few exchanges to >> google-caja-discuss@ (@gmail vs. @google membership issues). >> >> On Tue, Aug 12, 2008 at 4:48 PM, John Hjelmstad <[EMAIL PROTECTED]> wrote: >> >> > Hello, >> > >> > While beginning to refactor the rewriter APIs I've discovered that there >> > unfortunately is one semantic difference inherent to moving getContent() >> and >> > setContent() methods into the Gadget object (replacing >> > View.get/setRewrittenContent()): BasicGadgetSpecFactory no longer caches >> > rewritten content. >> > >> > I've written a discussion of this in issue SHINDIG-500, which tracks >> this >> > implementation sub-task: >> https://issues.apache.org/jira/browse/SHINDIG-500 >> > >> > To summarize: >> > 1. Is this change acceptable for the time being? >> > 2. I suggest that we can, at a later date, move fetching of gadget specs >> > into GadgetServer while injecting a Gadget(Spec) cache there as well, >> > offering finer-tuned control over caching characteristics. >> > >> > Thanks, >> > John >> > >> > >> > On Mon, Aug 11, 2008 at 2:20 PM, John Hjelmstad <[EMAIL PROTECTED]> >> wrote: >> > >> >> I understand these concerns, and should be clear that I don't (despite >> my >> >> personal interest in experimenting with the idea, agreed that we don't >> have >> >> time for it at the moment) have any plans to introduce this sort of RPC >> >> anywhere - certainly not in Shindig itself, as any such call would be >> hidden >> >> behind an interface anyway. >> >> >> >> Putting the RPC hypothetical aside, I still feel that there's value to >> >> implementing HTML parsing in terms of an interface: >> >> * Clearer separation of concerns/boundary between projects. >> >> - Corollary simplicity in testing. >> >> * Clearer API for content manipulation (that doesn't require knowledge >> of >> >> Caja). >> >> >> >> I could be convinced otherwise, but at this point the code involved >> seems >> >> of manageable size, so still worth doing. Thoughts? >> >> >> >> John >> >> >> >> >> >> >> >> On Mon, Aug 11, 2008 at 1:00 PM, Kevin Brown <[EMAIL PROTECTED]> wrote: >> >> >> >>> I agree with Louis -- that's just not practical. Every rewriting >> >>> operation >> >>> must work in real time. Caja's existing html parser is adequate for >> our >> >>> needs, and we shouldn't go out of our way to tolerate every oddity of >> >>> random >> >>> web browsers (especially as it simply wouldn't work unless you farmed >> it >> >>> out >> >>> to *every* browser). Any new code needs to be grounded in practical, >> >>> current >> >>> needs, not theoretical options. We can always change code later if we >> >>> find a >> >>> real need for something like that. We have real work to do in the >> >>> meantime. >> >>> >> >>> On Mon, Aug 11, 2008 at 12:06 PM, Louis Ryan <[EMAIL PROTECTED]> >> wrote: >> >>> >> >>> > John, >> >>> > >> >>> > From a practicality standpoint I'm a little nervous about this plan >> to >> >>> make >> >>> > RPCs calls out of a Java process to a native process to fetch a >> parse >> >>> tree >> >>> > for transformations that have to occur realtime. I don't think the >> >>> > motivating factor here is to accept all inputs that browsers can. >> >>> Gadget >> >>> > developers will tailor their markup to the platform as they have >> done >> >>> > already. I would greatly prefer us to pick one 'good' parser and >> stick >> >>> with >> >>> > it for all the manageability and consumability benefits that come >> with >> >>> that >> >>> > decision. Perhaps Im missing something here? >> >>> > >> >>> > -Louis >> >>> > >> >>> > On Mon, Aug 11, 2008 at 11:59 AM, John Hjelmstad <[EMAIL PROTECTED]> >> >>> wrote: >> >>> > >> >>> > > On Fri, Aug 8, 2008 at 6:10 AM, Ben Laurie <[EMAIL PROTECTED]> >> wrote: >> >>> > > >> >>> > > > [+google-caja-discuss] >> >>> > > > >> >>> > > > On Thu, Aug 7, 2008 at 9:27 PM, John Hjelmstad < >> [EMAIL PROTECTED]> >> >>> > wrote: >> >>> > > > > On Thu, Aug 7, 2008 at 3:20 AM, Ben Laurie <[EMAIL PROTECTED]> >> >>> wrote: >> >>> > > > > >> >>> > > > >> On Wed, Aug 6, 2008 at 11:34 PM, John Hjelmstad < >> >>> [EMAIL PROTECTED]> >> >>> > > > wrote: >> >>> > > > >> > This proposal effectively enables the renderer to become a >> >>> > > multi-pass >> >>> > > > >> > compiler for gadget content (essentially, arbitrary web >> >>> content). >> >>> > > Such >> >>> > > > a >> >>> > > > >> > compiler can provide several benefits: static optimization >> of >> >>> > gadget >> >>> > > > >> content >> >>> > > > >> > (auto-proxying of images, whitespace/comment removal, >> >>> > consolidation >> >>> > > of >> >>> > > > >> CSS >> >>> > > > >> > blocks), security benefits (caja et al), new functionality >> >>> > > (annotation >> >>> > > > of >> >>> > > > >> > content for stats, document analysis, container-specific >> >>> > features), >> >>> > > > etc. >> >>> > > > >> To >> >>> > > > >> > my knowledge no such infrastructure exists today (with the >> >>> > possible >> >>> > > > >> > exception of Caja itself, which I'd like to dovetail with >> this >> >>> > > work). >> >>> > > > >> >> >>> > > > >> Caja clearly provides a large chunk of the code you'd need >> for >> >>> this. >> >>> > > > >> I'd like to hear how we'd manage to avoid duplication between >> >>> the >> >>> > two >> >>> > > > >> projects. >> >>> > > > >> >> >>> > > > >> A generalised framework for manipulating content sounds like >> a >> >>> great >> >>> > > > >> idea, but probably should not live in either of the two >> projects >> >>> > (Caja >> >>> > > > >> and Shindig) but rather should be shared by both of them, I >> >>> suspect. >> >>> > > > > >> >>> > > > > >> >>> > > > > I agree on both counts. As I mentioned, the piece of this idea >> >>> that I >> >>> > > > expect >> >>> > > > > to change the most is the parse tree, and Caja's .parser.html >> and >> >>> > > > > .parser.css packages contain much of what I've thrown in here >> as >> >>> a >> >>> > > base. >> >>> > > > > >> >>> > > > > My key requirements are: >> >>> > > > > * Lightweight framework. >> >>> > > > > * Parser modularity, mostly for HTML parsers (to re-use the >> good >> >>> work >> >>> > > > done >> >>> > > > > by WebKit or Gecko.. CSS/JS can come direct from Caja I'd bet) >> >>> > > > > * Automatic maintenance of DOM<->String conversion. >> >>> > > > > * Easy to manipulate structure. >> >>> > > > >> >>> > > > I'm not sure what the value of parser modularity is? If the >> >>> resulting >> >>> > > > tree is different, then that's a problem for people processing >> the >> >>> > > > tree. And if it is not, then why do we care? >> >>> > > >> >>> > > >> >>> > > IMO the value of parser modularity is that the lenient parsers >> native >> >>> to >> >>> > > browsers can be used in place of those that might not accept all >> >>> inputs. >> >>> > > One >> >>> > > could (and I'd like to) adapt WebKit or Gecko's parsing code into >> a >> >>> > server >> >>> > > that runs parallel to Shindig and provides a "local RPC" service >> for >> >>> > > parsing >> >>> > > semi-structured HTML. The resulting tree for WebKit's parser might >> be >> >>> > > different than that for an XHTML parser, Gecko's parser, etc, but >> if >> >>> the >> >>> > > algorithm implemented atop it is rule-based rather than >> >>> strict-structure >> >>> > > based that should be fine, no? >> >>> > > >> >>> > > >> >>> > > > >> >>> > > > >> >>> > > > > >> >>> > > > > I'd love to see both projects share the same base syntax tree >> >>> > > > > representations. I considered .parser.html(.DomTree) and >> >>> .parser.css >> >>> > > for >> >>> > > > > these, but at the moment these appeared to be a little more >> tied >> >>> to >> >>> > > > Caja's >> >>> > > > > lexer/parser implementation than I preferred (though I admit >> >>> > > > > AbstractParseTreeNode contains most of what's needed). >> >>> > > > > >> >>> > > > > To be sure, I don't see this as an end-all-be-all >> transformation >> >>> > system >> >>> > > > in >> >>> > > > > any way. I'd just like to put *something* reasonable in place >> >>> that we >> >>> > > can >> >>> > > > > play with, provide some benefit, and enhance into a truly >> >>> > sophisticated >> >>> > > > > vision of document rewriting. >> >>> > > > > >> >>> > > > > >> >>> > > > >> >> >>> > > > >> >> >>> > > > >> > c. Add Gadget.getParsedContent(). >> >>> > > > >> > i. Returns a mutable GadgetContentParseTree used to >> >>> manipulate >> >>> > > > Gadget >> >>> > > > >> > Contents. >> >>> > > > >> > ii. Mutable tree calls back to the Gadget object >> indicating >> >>> > when >> >>> > > > any >> >>> > > > >> > change is made, and emits an error if setContent() has been >> >>> called >> >>> > > in >> >>> > > > the >> >>> > > > >> > interim. >> >>> > > > >> >> >>> > > > >> In Caja we have been moving towards immutable trees... >> >>> > > > > >> >>> > > > > >> >>> > > > > Interested to hear more about this. The whole idea is for the >> >>> > gadget's >> >>> > > > tree >> >>> > > > > representation to be modifiable. Doing that with immutable >> trees >> >>> to >> >>> > me >> >>> > > > > suggests that a rewriter would have to create a completely new >> >>> tree >> >>> > and >> >>> > > > set >> >>> > > > > it as a representation of new content. That's convenient as >> far >> >>> as >> >>> > the >> >>> > > > > Gadget's maintenance of String<->Tree representations is >> >>> concerned... >> >>> > > but >> >>> > > > > seems pretty heavyweight for many types of edits: in-situ >> >>> > modifications >> >>> > > > of >> >>> > > > > text, content reordering, etc. That's particularly so in a >> >>> > > > single-threaded >> >>> > > > > (viz rewriting) environment. >> >>> > > > >> >>> > > > Never having been entirely sold on the concept, I'll let those >> on >> >>> the >> >>> > > > Caja team who advocate immutability explain why. >> >>> > > > >> >>> > > >> >>> > >> >>> >> >> >> >> >> > >> > >
