From ec8996b8ecb3c1f64cd588a4db079378b099b56d Mon Sep 17 00:00:00 2001 From: Martin Jones Date: Wed, 16 May 2012 10:34:19 +1000 Subject: [PATCH] Document the dangers of executing the event loop in QML API Change-Id: I0294dd85fcc60615240a33c6e4a108fbde17a4bc Reviewed-by: Bea Lam --- src/qml/doc/src/performance.qdoc | 8 ++++++++ 1 files changed, 8 insertions(+), 0 deletions(-) diff --git a/src/qml/doc/src/performance.qdoc b/src/qml/doc/src/performance.qdoc index 91c9bbb..f6e56c9 100644 --- a/src/qml/doc/src/performance.qdoc +++ b/src/qml/doc/src/performance.qdoc @@ -47,6 +47,14 @@ never spend more than a couple of milliseconds per frame within blocking functio Failure to do so will result in skipped frames, which has a drastic effect on the user experience. +\note A pattern which is tempting, but should \e never be used, is creating your +own QEventLoop or calling QCoreApplication::processEvents() in order to avoid +blocking within a C++ code block invoked from QML. This is dangerous because +when an event loop is entered in a signal handler or binding, the QML engine +continues to run other bindings, animations, transitions, etc. Those bindings +can then cause side effects which, for example, destroy the hierarchy containing +your event loop. + \section1 Profiling The most important tip is: use the QML profiler included with Qt Creator. Knowing -- 1.7.2.5