W3C home > Mailing lists > Public > www-svg@w3.org > January 2003

Re: High-Quality Dynamic SVG Viewer

From: Chris Lilley <chris@w3.org>
Date: Tue, 21 Jan 2003 18:00:45 +0100
Message-ID: <189102717921.20030121180045@w3.org>
To: www-svg@w3.org, Tobias Reif <tobiasreif@pinkjuice.com>
CC: www-qa@w3.org

On Monday, January 20, 2003, 10:52:17 AM, Tobias wrote:


TR> Dean Jackson wrote:


>> I suggest the following to resolve the issue: [...]
>> - Provide explicit wording on the relationship between well-formedness
>>   and streaming. At the moment, the spec says that you can only
>>   render a well-formed document, which means that you can't do
>>   progressive rendering (since any partially downloaded file is
>>   not well-formed). The answer is to create a temporary well-formed
>>   version of the partial download (close all open tags, etc) and
>>   then render.


TR> This does not sound good to me. Requiring the application to do 
TR> guesswork will introduce lots of unforeseeable behaviour, AFAICS.

Yes it would, and this is not guesswork.

As soon as there is a well formedness error, then it goes into error
mode and stops rendering.

Or would you rather we said that no rendering can ever begin until the
whole file is downloaded - no, not even a loading screen, just plain
white ?

TR> If client apps are allowed or even required to do guesswork (especially 
TR> at such a relevant level), I might as well have a random algorithm code 
TR> my SVGs :|

You would need to explain why there is randomness here.

TR> Perhaps it would make sense to not require ~"closing all open tags, 
TR> etc", but instead specify a clear, simple, and most importantly much 
TR> less ambiguous algorithm.

The algorithm given is deterministic. During parsing, there is a stack
of open elements leading to the root. During progressive rendering of
a partially downloaded document, the display acts as if all of the
currently open elements were closed, in order, right up to the closing
root element.

TR> Something like:

TR>    For each subtree fragment which is completely parsed, the app can
TR>    decide if it has enough data to start/continue rendering/animation.

TR> Each "subtree fragment" is a well-formed XML document having one root 
TR> element; thus, there's no guesswork required to make it well-formed.

There is no guesswork needed to make it well formed anyway.

-- 
 Chris                            mailto:chris@w3.org
Received on Tuesday, 21 January 2003 12:00:53 GMT

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