This might the conventional wisdom, but the reality is that in a single thread, hiding data behind all sorts of obstacles is a huge detriment. If you can alrea

This might the conventional wisdom, but the reality is that in a single thread, hiding data behind all sorts of obstacles is a huge detriment. If you can already get to it, you might as well be organized so you can get to it easily. 'object oriented programming' (whatever it means exactly) is good for creating interfaces to data. The GUI might need an interface to its data, but the state of whatever is being processed and manipulated is less likely to need a special interface and almost definitely not whatever a component meant to display data provides. If you 'encapsulate' every tiny bit of information inside GUI components you end up with things like storing a string in a GUI label or storing a list in a list selection component. Then every time you want to access that information you have to extract it from the GUI, possibly keeping in mind the lifetime of the UI components.