Greetings,
I would like to present the following dilemma:
Let’s say one needs to use a Scroll as a main component of a Page. Everything goes well until the programmer needs to know the current scroll position of the Scroll (e.g. the viewport of the Scrollable it contains). The programmer already notices that there is a scrollTo() position, but there is no getScrollPosition() or similar.
The programmer then takes a look at the reference implementation of the Scroll and notices it can obtain the position of the scroll by hooking into Scroll's updateViewport(int x, int y, int width, int height). Problem is… that method is private.
Upon further inspection, it can be noticed that every member of the Scroll that provides its functionality is actually private, making extension by subclassing impossible. Thus, a third party programmer is unable to add any additional functionality by simply extending Scroll, which makes the widget pretty inflexible when more complex behaviors are needed.
The only solution to this problem I can think of is to create a 1:1 copy of the Scroll class, extending StyledComposite instead. Of course, creating a complete duplicate of a widget in order to add new functionality is not the best solution because it violates the DRY principle and future updates to the Scroll class would not reflect into the own implementation.
I would like to both ask for an alternative on how to solve this particular dilemma and suggest a possible improvement of the MicroEJ UI subsystem:
ej.widget.* could use more protected members, rather than private members in order to improve extensibility through inheritance. As they are currently implemented, they might as well be declared as final. This improvement would allow developing widgets which are based upon the vanilla ones, without having to recreate their behavior.
Thank you for your time,
Elian D.