[duped]

> I gave a look at other open source projects but I couldn't find any simplified one

Because there is no simple approach to this.

> Are there any documentation or open source projects to have look at?

Qt and JUCE are very mature and have the same architecture you're describing.

> at the top I have a Window class that handle all the widgets in a parent-child way relationship

Don't marry yourself to this architecture or else it's going to be a pain to support multiple windows or cases where the application does not own the window or its lifecycle.