[Interest] qml performance with Qt5.2

Nancy Zou Nancy.Zou at csr.com
Thu Jun 26 06:03:26 CEST 2014


Dear Gunnar & other friends:

I have read the blog http://qt-project.org/doc/qt-5/qtquick-visualcanvas-scenegraph-renderer.html
I have a few questions about section performance:
1 Make sure the texture atlas is used. The Image and BorderImage items will use it unless the image is too large.

if the qml use Image item to load a jpg or png file, how could I check whether it use texture atlas. How large is the image to make it can't use texture atlas. 

2 Clipping breaks batching . Never use on a per-item basis, inside tables cells, item delegates or similar. Instead of clipping text, use eliding. Instead of clipping an image, create a QQuickImageProvider that returns a cropped image.

If my display resolution is 800*480, the background image is 1280*600,  qml use image item to load the background image will be clipped. Is it right?
If I want to avoid clip, should I write a cpp file use QQuickImageProvider to return a cropped image? Does qml item can't do it?
One image item is usually a single batch, why the clipping can break it. 
Why different image items can't batch together? 

I am sorry to bother you for so much questions.

Best Regards
Nancy




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