Re: native JsType with constants

You need to remove initialization as well because the field by Java; the point is to link to the underlying javascript.

(A field that is defined by a native JsType is "native", meaning it is linked to underlying javascript and will generate code like 'canvas.nodeType == Node.ELEMENT_NODE')

On Sun, Dec 6, 2015 at 2:15 AM, rhmoller <rhmoller@gmail.com> wrote:

Just removing the final keyword does not work. It still complains about the initialization. I cannot remove the initialization because that is not valid Java.

The @JsOverlay solution looks OK. This line of Java

ctx.fillText("Canvas is an element node: " + (canvas.getNodeType() == Node.ELEMENT_NODE), 10, 20);

compiles to this line of Javascript

ctx.fillText('Canvas is an element node: ' + (canvas.nodeType == 1), 10, 20);

There does not seem to be any overhead from the overlay. It would have been nicer if it said (canvas.nodeType == Node.ELEMENT_NODE) in Javascript. But it evaluates to the same, so I am happy.


Den fredag den 4. december 2015 kl. 06.28.02 UTC+1 skrev Goktug Gokdogan:

Ignoring initialization is quite complicated when you put in to account generated clinit and also primitives which becomes compile-time-constants per jls and automatically inlined. Also code wise it is quite weird and potentially confusing.

Workaround is quite simple, just remove the "final" keyword and you are set.

On Thu, Dec 3, 2015 at 5:35 AM, Jens <jens.ne...@gmail.com> wrote:

Awesome. Thank you. @JsOverlay did the trick.

But IMHO @JsOverlay is only a workaround because it is meant to be used for code additions that do not exist in the underlying native type. So in your case GWT will now generate some additional code for your constants and will not use $wnd.Node.ELEMENT_NODE when doing comparisons. The link Thomas has posted is a good example of proper JsOverlay usage as the constant "TAG" is not part of the underlying native object.

So I would consider it a bug/missing feature that you can not define native constants in a native JsType. IMHO the restriction checker should allow static final constant initialization in native JsType and if constant is not annotated with @JsOverlay then GWT should treat the constant name as native constant. The value to initialize the constant in java code should be ignored, as initialization only exists to make java happy. 

cc @goktug

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