[erlang-questions] wxErlang - some answers

Frank Muller <>
Thu Jul 6 09:56:36 CEST 2017


Joe,

What about the idea behind "GTK server":
http://www.gtk-server.org/

Best
/Frank

Le mar. 4 juil. 2017 à 18:18, Joe Armstrong <> a écrit :

> I'm trying to get to grips with wxErlang so I toddled over to Ericsson
> and sat down for a few hours with Dan Gudmundsson and asked him a boat
> load of stupid questions.
>
> I'll be writing a lot more about this and setting up a github project
> to document how to get tame wxErlang ...
>
> Here's a first attempt at figuring out how things work.
>
> My usual approach to understanding things is always the same.
>
> "Take a program that works. Then remove non-essential bits until
> all that is left is so simple that you can understand it."
>
> How about making some buttons - this should be easy
>
> I started with demo.erl in ${ERL_TOP}/lib/wx/examples/demo/demo.erl
>
> This has some code for making buttons - but it also does *a lot more*
> and *it is highly redundant* -- from the point of view of learning the
> code volume does not assist comprehension, nor does using a generic
> behavior.
>
> What do I mean by this?
>
>    - ex_button.erl is written using wx_object.erl
>      so to understand ex_button.erl I have to also understand wx_object.erl
>    - ex_button.erl has repeated code. For example
>      several buttons have tooltips, but I only need to be shown how to do
> this
>      *once* not several times
>    - ex_button.erl introduces several new concepts - in particular spacers
>      and sizers - and I haven't a clue what they do.
>
> Now I'm going to refactor ex_button.erl so take a deep breath ...
>
> First refactoring: remove the dependency on wx_object
>
> I'd already figured out that a *minimal* wx windows program is:
>
>     start() ->
>         Wx = wx_win:new(),
>         Frame = wxFrame:new(Wx, -1, "Window Title"),
>         wxFrame:show(Frame).
>
> To make the window do something I'd want to write:
>
>     start() ->
>         Wx = wx_win:new(),
>         Frame = wxFrame:new(Wx, -1, "Window Title"),
>         setup_window(Frame),
>         wxFrame:show(Frame),
>         loop().
>
>     loop() ->
>         receive
>             Any ->
>                 io:format("Any=~p~n",[Any])
>         end,
>         loop().
>
> Given this structure I refactored ex_button.erl into buttons_demo.erl
> which removes all the wx_object code. So now I can stare are the code
> in buttons_demo.erl and see if I can understand it, for my point of
> view it's far easier to understand than ex_buttons.erl since there is
> no dependency on wx_object.erl
>
> Second refactoring: Simplify buttons_demo.erl
>
> The original program has four rows of buttons - but one will
> be sufficient for me.
>
> I now removed many lines of code, until only one line of buttons
> remained.
>
> The resulting code buttons_demo1.erl now only creates one line of buttons
> and has a couple of sizers.
>
> Dan told me that the line of code:
>
>    wxStaticBoxSizer:new(?wxHORIZONTAL, Panel,[{label, "wxButton"}]),
>
> Is wxWidgets way of making an hbox - Goodness wxWidgets can be build
> using Knuthian hboxes and vboxes (horray).
>
> I'm still not happy with buttons_demo1.erl since it mixes two ideas:
>
>    - making buttons
>    - putting buttons in a container and laying out the containers
>
> This needs to be refactored into:
>
>    - a pure button examples
>    - a pure layout example
>
> My intention is to try and decompose wxErlang into a large number of
> small examples, where each example illustrates one feature of the
> system. Also so show how to build complex examples from the small
> parts.
>
> I'll make all the code available on github so you can join in the fun
> (is this fun?).
>
> Notes:
>
> [1] Feel free to send me examples of wxErlang code - preferably
> one example per module that illustrates one feature.
>
> [2] Anybody want to do this for elixir?
>
> [3] The WxWidgets documentation is a terminological mess - they call
> *everything* (including a button) a window.
>
> [4] The WxWidget examples (in C++) require subclassing several objects
> resulting in multiple files per example - the Erlang equivalent is
> nicely contained within a single module (which is far nicer)
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> 
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>
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