[Interest] QML compiler?

[Harri Pasanen]

On 06/13/2012 11:07 PM, Till Oliver Knoll wrote:
> Am 13.06.12 22:03, schrieb Harri Pasanen:
>> I started working on a bit more substantial QML application for symbian
>> and ran into some issues.  One of these is the startup time with 10+ QML
>> non trivial files, and I'm not finished adding them.
> Wait a sec... what is a QML file, what does it contain? That's a simple
> "page" (window, dialog, ...) with buttons etc. on some mobile phone
> application, including animations and resources and some JavaScript
> logic, right?

Pretty much so.  Mainly UI stuff, most logic I already have in C++.

> So are you saying you already start hitting performance limits with a
> simple "10 pages application"? Doh!
>
> (Sorry when I say "simple" here - I'm trying to imagine how that should
> work out with *dozens* of dialogs and windows for a *medium* sized
> desktop application!)
As a rule of thumb I account for the mobile phone version being ~20 times slower than my Core i7 desktop. So if my application starts up in .5 seconds on desktop, it will take 10 seconds on the phone.  (That would be 1.3GHz ARM11, or 1GHz ARMv7.)

For most phone apps 10 seconds is not acceptable, but usually that can 
be worked around by using lazy loading, so the 10 secs is hidden away in 
a longer period.

> So I guess that's Qt 4.x? So any hope things will improve with Qt 5.x?
> Or is this an "initial parsing/compiling" problem where even the latest
> of greatest OpenGL ES 2.0 requirement that we already have and V8
> whatever JS optimisation engine can't help? :0

I suspect this is initial parsing/compiling.   Part of the issue is 
probably slower I/O, actually going to flash, opening files, reading 
etc.  I haven't done rigorous profiling yet.  Also I haven't tried with 
Qt 5.

Btw. does V8 use the JIT on mobile?   Is it selectable?

Harri