[...] I *think* that if you want flick support in your custom widget and the use case does not fit a built-in container (Flickable, ListView, etc.) you are supposed to implement that yourself. [...]
Also, one thing to watch for is that the mouse event coordinates are floats and you should convert them to integers as soon as possible before using them for other things. Otherwise bad things will happen - for example if you use them to move two different elements/layers during the pan by adding he position difference to x/y coordinates, the two elements/layers will gradually "float apart" due to floating point errors. All should be fine if you convert the mouse event numbers to integers first.
How do I build & run the demo app on desktop (Fedora 26 in my case)? Just load it to a recent QtCreator or is there more ? Don't really want to promise anything just now though - I'm already working on quite many things in modRana at the same time (routing overlay, making it possible to switch between different map element implementations, general stabilization so that a new modRana release can be made in a reasonably near future, etc.).