[erlang-questions] wxErlang - some answers

[Joe Armstrong]

I'd forgotten about the GTK server - I played with it years ago - has
anybody any experience with building this on various platforms?

/Joe

On Thu, Jul 6, 2017 at 9:56 AM, Frank Muller <frank.muller.erl@REDACTED> wrote:
> 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 <erlang@REDACTED> 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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