Replacement of QTScript continues

[Pedro de Carvalho Gomes]

Hi all,

I write to update about my work on replacing QTScript with QJSEngine.
I have just pushed to the branch a substantial change, which includes:
- fully functional Script console with JS console logging
- loading of old scripts (though with errors, depending on what's used)

If you have the interest, take a look at the working branch:
https://invent.kde.org/multimedia/amarok/-/tree/replace_Qtscript_with_QtQml

There's still quite some work ahead. At least if the goal is to
minimize changes to older scripts. The main issue is that the
QJSEngine API provides *way less* features than QScriptEngine. Also,
the documentation is not so complete.

One example: QScriptEngine had "newFunction" which allowed any
method/function to be exposed to the script engine. There's no such at
QJSEngine, but I managed to implement an equivalent solution by
1) creating a QObject with a Q_INVOKE method,
2) exporting the object: QJSValue scriptObj = engine->newQObject( myQObj );
3) get a reference to the method: QJSValue scriptFunction =
scriptObj.property("methodName");
4) create a global property to the method:
engine->globalObject().setProperty("functionName", scriptFunction);

The main issue I have now is that QJSEngine does not have an
equivalent to QScriptContext. This provides invocation information
that is necessary; especially a reference to the "this" JS object.
Without it I can't think of a solution that avoids rework at all
current scripts.

Another issue is that there's no direct equivalent to QtBindings.
These is specifically useful to manipulate QT widgets via script.
However those should naturally be replaced with some QML equivant,
though I couldn't look at it yet.

If there are more people interested, I'd be really glad to help bring
on board. There's a lot of fun stuff to work with.

Cheers,

Pedro