Support QPixmap from C++ in QML

The current solution for passing on a pixmap from c++ to the QML is QDeclarativeImageProvider. It is not clear why QDeclarativeImageProvider is required for a simple task. It is fairly common for models to pass icons per item. QML forces the user to create this "image scheme". A simple scheme like image://model/<row> doesn't work well for changing models. When rows are inserted/removed, the view will not requery all the items since data has not changed for the other items but now the items are shifted by one and the urls are thus different. The user is then forced to create a image://model/<unique-id>.

QTBUG-11980 explains why this feature does not exist. Unfortunately, I don't understand what it means. It says "The Image::pixmap property should be removed since it inherently causes memory issues. If a pixmap is created in a Qt application, passed to QML/JavaScript, and then not released by the Qt application, the memory used by the pixmap is never properly released." This is just expected behavior, isn't it? Why is this a problem? A new documentation section devoting to explaining the problem and possible solutions would be nice.

Ideally, return a QPixmap from C++ should just work out of the box.