Performance Tips & Tricks for QT/QML Apps: MeeGo Conference San Francisco, Hyatt Regency, May 23-25,2011

Performance Tips & Tricks for Qt-QML Apps Rajesh Lal, Nokia

High Performance QML Applications + = Qt Quick QML MeeGo Apps Qt UI Creation Kit Most Advanced UI High Performance2

Agenda QML Qt Quick 7 Tips Tools App3

What is Qt Quick • QML • IDE – Qt Creator • Qt UI Designer • Plugin for Mobility API • Quick Components The Fastest way to develop for MeeGo4

What is QML • Qt Meta-Object Language • JavaScript based • Qt Declarative runtime • CSS-JavaScript like syntax The Most Advanced UI technology for Mobile5

QML Powerful Declarative User Interface language6

QML Elements Graphics Animation Binding Items State Property Shapes Transitions JavaScript Text Transform. C++7

What is a Qt QML App Logic in JavaScript or UI in QML C++ API calls (main.qml) A Qt Container (main.cpp) Qt Quick Application8

Qt-QML App QML App. Viewer Property Bind 1+ QML Files JavaScript Import libraries Logic C++ Binding Import JS files UI 1 | 2 | 3 Qt Container(main.cpp)9

What is Performance • Short response time • High Throughput • Low utilization of resources • High availability • High Speed • Instant • Smoothness10

7 Tips for High Performance QML Application11

Tip 1 Divide and Rule12

1: Divide and Rule • Divide application UI into multiple QML files • Each Logical entity as a separate QML file • Think Object Oriented Programming • Do not use 1 Large QML file13

1: Divide and Rule Rule • Use main.qml as the main UI ₋ With different States & Transitions ₋ Create Multiple Views .QML files ₋ Import folders containing other QML files ₋ Local instances of imported QML elements14

1: Divide and Rule15

Tip 2 Load and Unload16

2: Load and Unload • Use Loader to control the memory usage • Load the absolute Minimum at the startup • Dynamically Load and Unload UI Components • Create Components when required17

2: Load and Unload18

Tip 3 Use Asynchronous Threads19

3: Asynchronous Threads • Use WorkerScripts for Remote API Calls • Use Threads for time consuming operations • Load large images asynchronously • Use caching for remote data/image (cacheBuffer in listview/Gridview)20

3: Asynchronous ThreadsLogin call in MyApp.QML MyAppScript/Login.QML file 21

3: Asynchronous ThreadsJs/dologin.js22

Tip 4 Optimize for Images (Greatest User of Memory)23

4: Optimize for Images • Optimize Images to reduce memory footprints • Specify exact size of the image • Avoid resizing/scaling an image in QML • Lazy load large images (asynchronous=true) • Don’t cache large images (cache=false) • Smooth filter = better visual quality, but slower24

Tip 5 Beware of String Operations25

5: Beware of String Operations • Strings are immutable • multiple + operator = multiple memory allocations • Use StringBuilder for more efficient strings • Define ₋ #define QT_USE_FAST_CONCATENATION ₋ #define QT_USE_FAST_OPERATOR_PLUS26

Tip 6 Know States, Transitions, & Animations27

6: Know States, Transitions, & Animations • In transition, animated area should be small • Animate different items sequentially when possible • Avoid multiple timers during animation • Avoid JavaScript operations during animation • Use ScriptAction & StateChangeScript28

Tip 7 Follow Best Practices29

7: Best Practices • For best performance use C++ instead of JavaScript • Insert properties at top of element declarations • Create application logic outside QML • Don’t build multiple layer of QML hierarchies • Use Qts i18n for internationalisation & localisation30

Tools QML Performance Monitor http://www.youtube.com/watch?v=XdI9C53uJw8 Valgrind http://valgrind.org/docs/manual/mc-manual.html QML Performance Guidelines http://doc.qt.nokia.com/4.7/qdeclarativeperformance.html31

Thank You @rajeshlalnokia

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Performance Tips & Tricks for QT/QML Apps: MeeGo Conference San Francisco, Hyatt Regency, May 23-25,2011

by Raj Lal on May 25, 2011

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Performance Tips & Tricks for QT/QML Apps: MeeGo Conference San Francisco, Hyatt Regency, May 23-25,2011 — Presentation Transcript