7 Jul
2016
7 Jul
'16
1:49 p.m.
On Thu, Jul 7, 2016 at 1:37 PM, Vincent Massol <vincent(a)massol.net> wrote:
Thanks for your reply.
I was just talking about how the provided listeners would be used. You
get the configured translations and create a chain from it.
On 07 Jul 2016, at 12:31, Thomas Mortagne
<thomas.mortagne(a)xwiki.com> wrote:
I don't think this is a AbstractBlockRenderer job to deal with transformations.
For me it means that when we want to filters the events we should not
use BlockRenderer at all and instead chain listeners. For example we
would refactor XWikiDocument#renderXDOM to create a chain of
ChainingListener (with the actual syntax PrintRenderer at the end)
content.traverse(myFirstListener).
Sure, but there are still 2 problems:
* It doesn’t solve this use case: offer a way for extensions to contribute some
transformation listeners that will be used everywhere. This is the use case we currently
have with Transformations. * It would duplicate 99% of the content of
AbstractBlockRenderer (the block traversal)
No, you just provide a helper for this.
My point is that it's not BlockRenderer job to execute translation,
this is a renderer.
I need to think more about it and especially by forgetting what we have and trying to
imagine how we would design this if we were starting from scratch. then, see if the result
can be incorporated without breaking everything.
At least do you agree with the need and that the Transformation implementation doesn’t
scale (and cannot scale), and that a solution done at render time would be better since
you’d traverse the tree only once?
Thanks
-Vincent
--
Thomas Mortagne
On Wed, Jul 6, 2016 at 10:33 PM, Vincent Massol
<vincent(a)massol.net> wrote:
> Hi devs,
>
> Rendering Tx are great to modify an XDOM into another XDOM.
>
> However they have a limitation: they’re slow (since you have to traverse the whole
AST). So if you have 10 Tx, you traverse the AST 10 times…
>
> I’d like to brainstorm about an alternative: the ability to register some Listener
that will get executed at render time and that will transform the events.
>
> Use cases
> ========
>
> Here are some example of Tx that would benefit being rewritten using this mechanism:
>
> * Icon Tx
> * Auto linking of JIRA id to jira issues
> * WikiWord Tx
>
> Implementation
> =============
>
> It could be something like:
>
> * Introduce a ConfigurableBlockRenderer interface with a addListener() method
> * Modify AbstractBlockRenderer to execute those Listeners before it calls its
PrintRenderer. This can be achieved with a composite listener that wraps the listeners
added and the PrintRenderer.
> * Have a way to register some Listeners in the configuration, that should be executed
when a page is rendered
> * Modify XWikiDocument so that those configured listeners are executed when rendering
a page
>
> Differences between Tx and Listeners
> ==============================
>
> * Tx are slow but easy to write since you have access to the whole AST
> * Listeners are harder to write since you need to store the events if you need to
remember them (but we have developed some tools already over the years such as the
LookaheadListener)
> * Listeners depend on their order and they should be written carefully to minimize
their interdependencies
> * Listener will get executed only at render time so you need to render to get the
modifications to the tree, while Tx are independent of rendering.
>
> WDYT? Do you see a better way to achieve the same goal (ie removing the Tx
performance limitation)?
>
> Thanks
> -Vincent
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