[Qt5-feedback] QML-related wishlist

[Jason Kinzer]

Yeah... on point (3), even just writing it I was beginning to glimpse the
level of change involved, the likely performance penalties, and how the QML
JSON-style syntax doesn't necessarily lend itself well to other languages
(e.g. python). Hence the "pie in the sky" designation (can't you guys work
miracles?? ;-)

Thanks for your response.

Jason

On Thu, May 12, 2011 at 3:27 AM, <lars.knoll at nokia.com> wrote:

>
> 2 - Improve QML performance for 'trivial' expressions (less important)
>
> I've noticed there appear to be 2 engines used in QML (at least when I dove
> into the code a few months back): the standard JSC engine, and then a
> 'fast-path' interpreter for very simple expressions (e.g. 0+1). This is nice
> because from my experimentation in such simple cases the overhead of
> invoking the JS engine far exceeds the time required to compute the
> expression. However, my annoyance is that the current fast path is very,
> very limited and it's incredibly easy to break it so that it reverts back to
> the primary engine. My point: it would be great if this fast path were
> improved (tho I'm not sure what new tradeoffs V8 introduces... maybe the
> invocation overhead will be lower?)
>
>
> There's work ongoing in this direction. Checkout
>
> http://qt.gitorious.org/+qt-developers/qt/qtdeclarative-staging/trees/qtquick2/src/declarative/qml/v4
>
>
> 3 - Provide abstraction layer for the QML engine binding (pie-in-the-sky)
>
> I understand this team's desire to focus 100% on Javascript. However, what
> I would love is for QML to expose a service provider interface that provides
> all the calls/callbacks required a scripting engine. Such an SPI would allow
> the community to introduce bindings for other languages. And yeah, I
> understand there is then still the editor issue - ideally QT Creator would
> also have an interface factored out for it's QML editor so we can introduce
> QML editors that accept the syntax for other languages.
>
>
> That's the one thing I'm not really willing to consider. The right hand
> side of every binding is a JS expression. Changing that to another language
> would change everything in QML, confuse developers and create all together a
> pretty ugly looking Frankenstein. In addition, this is one of the most
> performance critical pieces in QML, and trying to add abstraction layers in
> these places is rarely a good idea.
>
> Cheers,
> Lars
>
>
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