ActiveQt components are not well behaved when unloading/reloading

ActiveQt components are not well-behaved when unloading/reloading the component DLL.

Static changes made in one ActiveQt app live past the unloading of the DLL and can cause crashes when loading a new ActiveQt app. Such changes include, but are possibly not limited to:

• Registered meta types
• Registered QML types
• Loaded QRC files

Such a crash can easily be reproduced:

• Run ActuveQt testcon project
• Load the simpleqmlax example project
• Close the simpleqmlax control
• Load the simpleqmlax example project again
• Observe crash

Attached is another example project simpleqmlapp. Both simpleqmlapp and simpleqmlax load a QML file from qrc:/main.qml, and they both register a type Controller through qmlRegisterType. The following unwanted behaviour is observed.

• Run ActuveQt testcon project
• Load the simpleqmlax example project
• Load the attached simpleqmlapp example project
• The new control tries to load simpleqmlax's main.qml
• The new control tries to load simpleqmlax's Controller

Also,

• Run ActuveQt testcon project
• Load the simpleqmlax example project
• Close the simpleqmlax control
• Load the attached simpleqmlapp example project
• Observe crash

Furthermore, if the ActiveQt control is loaded when there is no running QApplication, the ActiveQt control will create one first - otherwise it will hook up to an existing application. However, the deletion of the QApplication in the ActiveQt DLL is flawed.

• It does not run the deferred deletion which QCoreApplication::exec normally does.
• It does not care if another ActiveQt component has been loaded in the mean time, meaning that it can kill an unsuspecting component.