In a Qt application embedding QtQuick components, the BusyIndicator will under some conditions go to the running state without being asked to.

The QtQuick component (a QtQuickWidget) needs to be a child of a QTabWidget. When switching tabs, the BusyIndicator will go in the spurious running state.

This minimalistic app demonstrates the problem:

busy.pro

TEMPLATE = app
TARGET = busy
 
QT = core gui widgets quickwidgets
 
SOURCES += main.cpp

main.cpp

#include <QApplication>
#include <QQuickWidget>
#include <QTabWidget>
#include <QUrl>

QQuickWidget *createQuickWidget()
{
 QQuickWidget *qw = new QQuickWidget();
 qw->setResizeMode(QQuickWidget::SizeRootObjectToView);
 qw->setSource(QUrl::fromLocalFile("busy.qml"));
 return qw;
}

 
int main(int argc, char **argv)
{
 QApplication app (argc, argv);

 QTabWidget tab;
 tab.addTab(createQuickWidget(), "Tab1");
 tab.addTab(createQuickWidget(), "Tab2");
 tab.show();

 return app.exec();
}

busy.qml

import QtQuick 2.4
import QtQuick.Controls 1.4

Item {
  MouseArea {
    id: mousearea
    anchors.fill: parent
  }
  BusyIndicator {
    running: mousearea.pressed
  }
}

Place all three files in a directory and run : qmake & make
Run the app with ./debug/busy[.exe]

To reproduce:

• click inside one of the tabs to run the BusyIndicator at least once
• switch tab
• come back to 1st clicked tab ==> BusyIndicator should run
• click tab again to stop BusyIndicator
• repeat

This issue has been reproduced with the minimal example on Qt 5.6.1 (msys2).
This issue affects our real application on Qt 5.6.0 (msys2 and ubuntu)