More GUI (ravings?)

Vlad Dumitrescu (EAW) <>
Mon Mar 3 11:32:57 CET 2003

Hi all,

Since I am working on ex11, I am also trying to see what might come ahead and try to plan for a possible widget toolkit, implemented in Erlang. As I said once before, I can't see any way to do it in a different way that it is done in most other languages, that is OO or the like. Please if there is anyone that has a link to a GUI framework that isn't OO (but not too far from Erlang's philosophy either), send it to me.

The "missing feature" that would be needed has already been discussed here in many ways: building a hierarchy of behaviours. Or with another word, implementing subclassing. A generic window has behaviour that an input widget will "inherit" and that one can further be refined to become a "password input" widget. 

The question is how to delegate the "inherited" behaviour to the right implementation module?

One way is to just write lots of funs similar to
	set_visible(Widget) ->
But this seems very heavy on the typing fingers and not extendible. Maybe some macros could help, but it would look like a C++ framework from 

Another way is to use for example an attribute
and then either:
   * change error_handler:undefined_function to check any modules named in 'inherits' for the respective function before reporting an undef error
   * let the compiler generate the stubs above, but then only one "parent" can be used.

Yet another way would be writing behaviours on top of other behaviours, and also let one process implement several behaviours.

Or even modify the language to allow for generic functions (à la Lisp) that can be extended from another module than the one they were originally written in. 

I am reluctant to use the term "inherit" but I found none better. What is needed is indeed a behavioural inheritance, which might not have anything to do with objects and classes as we learned to love/hate them :-)

I don't think I am completely out in the bush, but if I am, please let me know. :-) I will have to give this more thought, but I feel some feedback will be useful.

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