Well, it would work like: The child class comes with all its parents components laid out in there. Then you can add components or modify existing ones (moving them around, or make the caption italic instead of regular).
Indeed, hiding controls would be only usefull in edge cases (but they exist).
Well, I cant give you a good C++ example (because I dont know any C++), but it would be like the “TWinControl” or “TCustomControl” class in Delphi.
In the example above, I would take the Percentile widget, create a child, call it “CaptionedPercentile”.
If I wouldnt do anything with it, it would just look like a “normal” percentile, with all its widgets (bar, icon, etc).
I then add a text component to be placed at the top.
Then in the constructionscript of the child widget, which is run after its parent construction script, I would move the position of the (inherited) percentile widget down a bit, under the caption.
Yes, so a quick changein style to the base class would propagate through all child classes.
Imagine you have 50 percentile displays in a screen and then decide to tweak the appearance. You would have to redo the tweak 50 times for each iteration… Thats just not feasible…