[Development] The place of QML

[Uwe Rathmann]

On 05/18/2012 07:36 AM, Иван Комиссаров wrote:
> Btw, you're saying that painter technology is outdated?

Well it is also the API for rendering PDF ( and other paint devices ) 
documents. Having common code for screen and PDF rendering is absolutely 
not outdated - and is possible using QSGPaintedItem.

I would be careful with terms like "outdated". In the end the desktop is 
the concept of the 90s ( widget are much older ) and the current 
desktops are the part that doesn't work on smartphones alike devices.
But are keyboard and mouse outdated - only because smartphones and 
tablet devices don't have one - or why should a scene graph based 
application be more modern, when it runs inside of a Xfce/X11 desktop ?

The controversal discussions about modern desktop environments indicate 
that they are not progress for everyone and the expectation that 
concepts from smartphones will be the future on all type of desktops ( 
what is somehow implied in "QPainter is outdated" ) won't necessarily 
happen.

Maybe this is where the "code once deploy everywhere" idea has an end 
and we will return to having different GUIs for different environments.

> What speedup provides QML scene graph? According to this http://labs.qt.nokia.com/2011/05/31/qml-scene-graph-in-master/ article, speedup is 2.5 times. As for me, it's just a constant optimization, it is not reduces complexity very much, as for me.

With raster QPainter::drawPolygon is significantly faster than 
QPolygonF::drawPolygonF. QPolygon::drawPolygon on Qt3/X11 is only a thin 
wrapper around X11 methods - something you can't beat performancewise. 
But by far the best performance you will have when you can reduce the 
number of points before drawPolygon on is called.

What I want to say with this is: speedup numbers heavily depend on the 
use case and often doesn't mean much for your application.

Uwe