book: Explain final types

gtk-rs / gtk4-rs

Rust bindings of GTK 4

https://gtk-rs.org/gtk4-rs/

MIT License

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book: Explain final types #957

Open Hofer-Julian opened 2 years ago

Hofer-Julian commented 2 years ago

People are currently surprised that they can't subclass certain types.

Explain the concept of final types
Show how to find out whether your type is subclassable (e.g. by checking https://gtk-rs.org/gtk4-rs/git/docs/gtk4/subclass/index.html)
Show how to use final types:
- By subclassing from gtk::Widget or adw::Bin
- Then adding the final type as child

bilelmoussaoui commented 2 years ago

I would avoid the usage of adw::Bin because it sets the layout manager as BinLayout and you will have to unset that in order to have a custom measure vfunc for your widget. Widget should be good enough

Hofer-Julian commented 2 years ago

I would avoid the usage of adw::Bin

I've been seeing adw::Bin often when people wanted to use a certain final type with a composite template. Seems like in that case they just wrapped it in a adw::Bin. Do you mind that use case as well?

bilelmoussaoui commented 2 years ago

I would not recommend that at least for now. People should learn to unparent their widgets on dispose and the book is the perfect place for that