Linked by Hadrien Grasland on Sat 15th Jan 2011 18:02 UTC
Graphics, User Interfaces As an answer to someone asking whether Unity will require a working OpenGL stack to operate in Ubuntu 11.04 "Natty Narwhal", Mark Shuttleworth announced that Canonical would offer an optional, QT-based, "2D" implementation of Unity. Here is a video, too.
Thread beginning with comment 458359
To view parent comment, click here.
To read all comments associated with this story, please click here.
RE[5]: Future of Compiz
by vivainio on Sun 16th Jan 2011 10:14 UTC in reply to "RE[4]: Future of Compiz"
vivainio
Member since:
2008-12-26


comparison with QML (on set top box) : QML couldn't just draw and scroll a list with 6 items (with no graphic options, that is, it was roughly just a list of strings). No problem with the EFL and a bunch of graphics effects.


Citation needed, please. What hardware? QML can scroll huge lists with graphics just fine (even on older phones). Misconfiguration, perhaps?

Reply Parent Score: 5

RE[6]: Future of Compiz
by vtorri on Sun 16th Jan 2011 17:02 in reply to "RE[5]: Future of Compiz"
vtorri Member since:
2007-03-05

"
comparison with QML (on set top box) : QML couldn't just draw and scroll a list with 6 items (with no graphic options, that is, it was roughly just a list of strings). No problem with the EFL and a bunch of graphics effects.


Citation needed, please. What hardware? QML can scroll huge lists with graphics just fine (even on older phones). Misconfiguration, perhaps?
"

hardware: x86 @ 1Ghz + sgx 530 + 1GB of ram

The company who tried it used a list of 5 items with animations. 100% of CPU used, the fillrate was huge. They removed all the animations (so the simplest list), the animation was not smooth at all, with still a huge amount of used CPU.

The 1st design problem in QML is that there is one Javascript context per object (creating one costs a lot). You can't cache and reuse an object (you have to destroy it, then recreate it, and as creating one object is slow...). So you can't even cache the items of a scrolling list to have good speed on slow devices.

The 2nd design problem (not related to speed or memory consumption) is that they embed in one object the UI and the code. Which means a code that is not easy to maintain (while it would have been a better choice to separate the UI from the code)

After one year of development, trying to improve QML code, the company gave up and used something else.

Is there a video of a scrolling list on old phones that shows the smoothness of QML ?

Reply Parent Score: 1

RE[7]: Future of Compiz
by vivainio on Sun 16th Jan 2011 18:39 in reply to "RE[6]: Future of Compiz"
vivainio Member since:
2008-12-26


hardware: x86 @ 1Ghz + sgx 530 + 1GB of ram


N900 uses hardware inferior to that, and QML is pretty smooth there.

Here's an example I saw just today:

http://www.youtube.com/watch?v=ak-Py3cf_Ac


The 1st design problem in QML is that there is one Javascript context per object (creating one costs a lot).


Not true. You can create a global js context by doing ".pragma library" in the .js file.


You can't cache and reuse an object (you have to destroy it, then recreate it, and as creating one object is slow...).


QML actually can actually cache list elements:

http://doc.qt.nokia.com/4.7-snapshot/qml-listview.html#cacheBuffer-...

The 2nd design problem (not related to speed or memory consumption) is that they embed in one object the UI and the code. Which means a code that is not easy to maintain (while it would have been a better choice to separate the UI from the code)


I don't know what you mean by this. You can call out to javascript and c++ components from your qml components.


After one year of development, trying to improve QML code, the company gave up and used something else.


One year, and they didn't contact Nokia at all for help? It seems to me that any problems they encountered should be pretty simple to solve.

Is there a video of a scrolling list on old phones that shows the smoothness of QML ?


Most of the videos seem to have N900, but I've been running my "QmlReddit" application ok on N97 mini. It's not 60fps, but it can do okay anyway. Perhaps I could make a video someday.

OTOH, N900 is old tech today as well ;-).

Incidentally, once we switch to QSceneGraph the performance will be much greater still:

http://www.youtube.com/watch?v=n3W5O2biSPU

Reply Parent Score: 4

RE[7]: Future of Compiz
by cdude on Sun 16th Jan 2011 21:56 in reply to "RE[6]: Future of Compiz"
cdude Member since:
2008-09-21

> After one year of development, trying to improve QML
> code, the company gave up and used something else.

Are you aware that QML was introduced with Qt 4.7 and 4.7 is only since a few months around?

Reply Parent Score: 1