How to Qt - Qml debugging and/or profiling?

Question

What software Qt/QML pieces are needed to compile in an app to be able to debug/profile QML?

My current app is build using cmake and runs on a embedded device. Furthermore, I'm starting to use Qt 4.8.3 (until now 4.7.0).

I would like to use these fancy/cool features (for an embedded developer):

http://doc.qt.digia.com/qtcreator/creator-qml-performance-monitor.html

I've searched trough qt-project looking for help, but I haven't got clear what are the steps needed when you want to debug/profile a remote app, with a customize build environment.

So, I would like to know if it is needed any of the following steps, and in positive case, what is in fact the needed code.

• Qt libraries ./configure specific options.
• QtCreator specific options to attach/launch to remote app.
• Cmake includes and libraries needed in the final app executable .

Any help, link, etc is welcomed.

Answer 1

Checking the docs all given answers seem to be unnecessary. Further it hardcodes debug code in releases. I have no clue why QQmlDebuggingEnabler would be necessary, but if you check the code here and here, you will recognize, that the instatiation of QQmlDebuggingEnabler is not necessary. Just include QQmlDebuggingEnabler and set the QT_QML_DEBUG flag e.g. like this (CMake)

set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -DQT_QML_DEBUG ")

However according to the docs QQmlDebuggingEnabler is not necessary.

Furtermore: profiling unoptimized code makes no sense.

For me setting QT_QML_DEBUG as flag and checking the checkbox for QML debugging is sufficient.

Answer 2

I'm using Qt 5, and it got even easier. Just this one step was required on my side to do QML profiling:

#include <QQmlDebuggingEnabler>

...

QQmlDebuggingEnabler enabler;