Apart from the examples in the Custom Views sub-section within the Scheduler' How To
documentation section, which the article Dimitar linked is part of, there isn't an article that provides extensive explanation on extending built-in views. The documentation is focused on explaining the built-in features and API of the widgets, rather than on the ways they can be extended by overriding their default behavior. Custom views can be different and would depend on the specific scenario and requirements, thus the articles in the HowTo section simply demonstrate particular scenarios, rather than being tutorials for creating custom views.
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