For Object and Embed tags, Dart needs to hand all attributes and methods to the element unmodified.

[DartBot]

This issue was originally filed by jeffbailey@google.com

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What steps will reproduce the problem?

  nethackEmbed = new Element.tag('embed');
  nethackEmbed.on['message'].add(handleMessage);

allows me to correctly receive messages for a NaCl-compiled C binary. However, the postMessage method isn't available and causes a run-time error:

  nethackEmbed.postMessage('bob');

Uncaught NoSuchMethodException - receiver: '[object Object]' function name: 'postMessage' arguments: [bob]]
$thrownethack.js:96
Object.noSuchMethodnethack.js:138
$varMethod.Objectnethack.js:234
$varMethod.Object.(anonymous function)nethack.js:6
handleMessagenethack.js:3467
wrappednethack.js:3076
wrap$1nethack.js:655
isolate$Isolate.runnethack.js:555
wrap$1nethack.js:654
(anonymous function)

What is the expected output? What do you see instead?

A message should be sent through the the embedded NaCl object.

What version of the product are you using? On what operating system?

URL: http://dart.googlecode.com/svn/trunk/dart/client/html
Repository Root: http://dart.googlecode.com/svn
Repository UUID: 260f80e4-7a28-3924-810f-c04153c831b5
Revision: 1684
Node Kind: directory
Schedule: normal
Last Changed Author: dgrove@google.com
Last Changed Rev: 1334
Last Changed Date: 2011-11-08 15:01:24 -0800 (Tue, 08 Nov 2011)

with one custom patch:

Index: frog/lib/json.js
===================================================================

--- frog/lib/json.js (revision 1684)
+++ frog/lib/json.js (working copy)
@@ -23,6 +23,7 @­@
   if (obj != null && typeof obj == 'object' && !(obj instanceof Array)) {
     return $fixupJsObjectToDartMap(obj);
   }

• return obj;
   }
   
   // Converts the parsed JavaScript Object into a Dart Map.

This is compiled with Frog, on Ubuntu.

Please provide any additional information below.

[DartBot]

This comment was originally written by jeffbailey@google.com

[DartBot]

This comment was originally written by bradnelson@google.com

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So on further investigation, it appears that what's happening is that frog/dart is entertaining the possibility that postMessage will be allowed on the nacl embed tag because it 'might' be an instance of the html5 postMessage method on window. For instance if jeff changes postMessage to foo, then it gets a compile time error.

Questions:

1. I was under the impression that embed/objects could have arbitrary members/properties for example an npapi plugin has the ability to respond to interrogation has to what it supports. Does dart have some accommodation for this?
2. Nacl / ppapi folk, is nacl grafted into chrome in some peculiar way? I assume that use of postmessage was just a attempt at homogeny with html5 similar mechanism. Or is it actually masquerading as something that might confuse dart's runtime?

[DartBot]

This comment was originally written by dmichael@google.com

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Attempts to answer:

1. That's correct; an NPAPI plugin can expose any properties (incl. functions) it pleases, and it's not possible to enumerate them statically. (NaCl apps aren't able to do this, but other plugins e.g. Flash do this even with PPAPI)
2. The current NaCl integration is just a trusted PPAPI plugin. Even for trusted PPAPI, 'postMessage' is exposed to JavaScript pretty much the same way as a plugin would do (using NPAPI functions in WebBindings). It only 'looks' like normal postMessage. It might be possible to get the Embed element to implement the MessagePort interface, but it would take a change to the spec or at least convincing WebKit maintainers that it's a good idea. I'm not really even convinced myself.

[DartBot]

This comment was originally written by jeffbailey@google.com

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Thanks. I ran into Ian Hickson at lunch and he pretty much told me the same thing.

So it sounds like in the case of either and embed or an object tag, Dart needs to just wrap the call in a try block and hand things over verbatim.

Retitling this bug to reflect that.

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Changed the title to: "For Object and Embed tags, Dart needs to hand all attributes and methods to the element unmodified.".

[vsmenon]

As others have alluded, there are two issues here:

(1) Can/should plugins expose functionality to Dart?
I do not think we provide APIs for this today.

(2) If so, what should it look like in Dart?
It might not look like JavaScript. HTMLEmbedElement doesn't have a statically defined postMessage, so we do not declare one in Dart. Unlike JS, you cannot add your own methods or fields to an object after the fact. E.g., it might look more like:

nethackEmbed.invoke('postMessage', ['bob']);

@bradnelson: You're right about frog and postMessage. Frog is doing some simple compile analysis. It cannot (currently) prove that nethackEmbed doesn't have a postMessage method at compile time, but it can prove that it does not have a foo.

[DartBot]

This comment was originally written by jeffbailey@google.com

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Are there docs on how client/dom and client/html are generated and how to tell which ones Frog uses? I'm trying to piece together a patch to support .invoke, and I'm editing various generated files at the moment.

[vsmenon]

We're working on getting the docs out. In the meantime, client/dom/frog/frog_dom.dart and client/html/release/html.dart are the libraries pulled in by the frog compiler.

[DartBot]

This comment was originally written by drfibonacci@google.com

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Removed Type-Defect label.
Added Type-Enhancement, Area-Frog, Triaged labels.

[DartBot]

This comment was originally written by jeffbailey@google.com

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I'm not sure about classifying this as an enhancement rather than a defect. I have a DOM node that I can't interact with and there's no work around. Seems like a bug to me.

[DartBot]

This comment was originally written by jeffbailey@google.com

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Assigning per jacobr. Jacob notes that this should be implemented using "No Such Method" and some of the changes to the Dart/JS Native Interface.

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Set owner to @jmesserly.

[jmesserly]

Set owner to @rakudrama.

[anders-sandholm]

Removed Area-Frog label.
Added Area-Dart2JS, FromAreaFrog labels.

[kasperl]

Is this a DOM issue, Stephen?

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Removed Area-Dart2JS, FromAreaFrog labels.
Added Area-DOM label.

[vsmenon]

I don't think anyone is actively depending on this right now. Let us know if it's a blocker.

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Added this to the Later milestone.

[DartBot]

This comment was originally written by jeffbailey@google.com

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I was depending on this but am not any longer (I've dropped Dart because of this and other issues. It's too much work to keep up with postprocessing the output)

[iposva-google]

Removed Area-DOM label.
Added Area-HTML label.

[vsmenon]

Removed the owner.

[DartBot]

This comment was originally written by joh...@johnmccutchan.com

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Hi,

I need to be able to communicate from Dart to a NaCl plugin and I'm blocking on this. Who is working on this?

Thanks,
John

[sethladd]

John has a killer bullet physics demo that we'd love to port to Dart + NaCL. Hoping we can move this to "sooner" rather than "later". Thanks!

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cc @blois.

[sethladd]

Not planned.