[Seaside] Strategies for bulky renders/updates

[Levente Uzonyi]

On Sun, 13 Mar 2011, radoslav hodnicak wrote:

> I've been using seaside with jquery to create quite interactive
> interfaces, using the simplest approach of "everything has its own
> callback". This works well if the dataset you're working with is
> small, but I'm now venturing into territories where it takes seconds
> to receive+render a page, which isn't acceptable.
>
> For an example of what I'm talking about imagine a page showing a list
> of emails. Every line (email) has a clickable sender, subject, date,
> and a bunch of more actions and icons etc. If you're creating
> anchors/click actions for each field separately, that's easily
> hundreds or thousands of callbacks per page, each needing to be
> generated on the server and sent over the wire. So clearly I need to
> instead write client side javascript that will figure out what the
> user clicked and do a parametrized request. Which I can do, but I'm
> wondering if someone has figured out a clever way how to map the
> information on the page to smalltalk objects on the server (other than
> using callback registry). Same goes for bulk actions involving
> multiple items ("delete selected" and the like).

We implemented a hack, that does the following:
Instead of Seaside callbacks we implemented our own lightweight callbacks 
on top of Seaside's.
We have a method, that accepts a block and a seaside canvas. The receiver 
(typically a WAComponent) of the message has an OrderedCollection which 
stores the callback blocks.
When you send the method, it adds the block to the collection and returns 
a piece of javascript which calls a function with the index of the block 
in the collection. The returned javascript code is passed to #onClick:, 
#onChange:, etc. Something like:

 	html button
 		onClick: (self
 			lightweightCallBackOn: html
 			do: [ self buttonClicked ]);
 		with: 'Click me!'

The generated html will be something like:

<button onclick="c1lc(1)">Click me!</button>

The javascript function (c1lc in this case) is built using Seaside's js 
code generator when the page is rendered and it's added with 
#addLoadScript: to page.
The generated function triggers a Seaside JQuery callback. The callback 
accepts the index as argument, looks up the block by index and evaluates 
it.


Levente

>
> rado
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