[Interest] Qml bindings with javascript library functions in them

[Alan Alpert]

Bindings do not update when a purely JS variable changes, it can only
respond to changes in QML properties. You could bind to something like
 stateObject.value, and still be able to use
JS.setValue(stateObject.value + 1) if you wanted. But without going
through C++ though you couldn't make stateObject.value read-only to
everything but the setValue function.

This is more of a bug than a feature, and support for reevaluating
bindings to JS objects is planned for an unknown future release.

If you want to force a re-evaluation from C++, you can always expose a
C++ property of "forceUpdate", rewrite your expressions to be
"forceUpdate + JS.setValue(...);", and emit the notify signal for
forceUpdate;

--
Alan Alpert

On Thu, Jun 13, 2013 at 11:29 AM, Josh Faust <jfaust at suitabletech.com> wrote:
> Hey all,
>
> I have a javascript library, with functions that are used in a lot of
> bindings. I'm trying to get those bindings to reevaluate when some variables
> used inside the functions change. A simple example:
>
> // JS.js
> .pragma library
> var _Value = 0;
> function getValue()
> {
>   return _Value;
> }
>
> function setValue(val)
> {
>   _Value = val;
> }
>
> ...
>
> // in use
> Column {
>   Text {
>     text: JS.getValue()
>   }
>
>   Button {
>     onClicked: JS.setValue(JS.getValue() + 1)
>   }
> }
>
> When _Value changes, I'd like the QML binding to reevaluate. At the moment
> it doesn't look like it will -- and even using JS._Value directly, and
> modifying it directly, none of the bindings reevaluate. Is this expected? Is
> there any way for me to force reevaluation of these bindings (I'd even be
> happy forcing a re-evaluation of all bindings from C++ -- this is for a
> development-time feature, so performance is not a concern).
>
> Thanks
>
> Josh
>
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