[Ur] calling javascript code in <dyn>

[Adam Chlipala]

Let me try to disentangle the potential parts of your question.

I hope you are not asking about literally writing code in JavaScript.  I 
will proceed as though you are actually asking about /client-side code/, 
but let me know if I misunderstood.  (It is a rather nice feature of 
Ur/Web that writing Ur/Web programs need not involve JavaScript at all, 
anymore than we talk about "transistors" when reading JavaScript code!)

So, then, I conclude that your question is how to add a listener on a 
[source], to run arbitrary client-side code whenever the source 
changes.  You seem to be on a good track there, with the mention of a 
dummy node.  I would create a <dyn> node that generates only a <script> 
node, whose 'code' handler will then be run whenever the source changes, 
such that this <dyn> node contributes no content to the page.

On 07/04/2018 04:10 PM, Fabrice Leal wrote:
> is it possible to trigger javascript code when calling 'set s ...' ?
>
> as i understand the main usage seems to be regenerating html node 
> trees; i think i could get away with generating some dummy html node 
> with the javascript call in onload event, but I'm asking just to make 
> sure I'm not missing anything.
>
> my goal is, for instance, to update some state on the client side and 
> trigger a canvas redraw,
> since i seem to be unable to call '... <- signal s;' inside a 
> 'transaction page'

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