[erlang-questions] My quest for a decent way to make a GUI in erlang

Joe Armstrong <>
Wed Jul 26 22:57:48 CEST 2017


One other point that I omitted to make

When I wrote ex11 (a graphics experiment) I realised that
3D objects with behaviour are *really* just 2-D objects + time.

A button is just a rectangle with a shadow draw round it. When you
click it it moves down and the shadow changes, a little while later it returns
to its original position.

I wanted to make a tabbed widget - now you might think that I could
combine buttons in some kind of hbox - well yes you can but it looks
terrible. No a tabbed widget viewed as a 2D drawing is "just" a line
that moves up and down and a few shadows in the appropriate places.

So the way to make a tabbed widget is *not* to compose a hbox of buttons
but to draw the outline of what you want in 2D and make some regions that
are sensitive to mouse clicks.

The abstractions you think you need (buttons, sliders) are not the ones that
are useful from a compositional point of view.

This is actually why I like SVG - there are two abstractions path and group
- path draws a curve. Group glues objects and has an optional affine
transformation. All other SVG objects (rectangles, circles, lines,
...) can
be constructed from paths and groups.

Postscript is another *great* and not very well understood language -
display postscript would be great for GUIs but which is sadly not used.

It's crazy - in the browser it's really easy to mock up an interface
with SVG or a canvas or by adding things to the DOM - but on the
desktop it's a pain in the whatnot.

The answer is *not* to bundle the entire browser into a stand alone app
but to strip out the good parts  and make a minimal system with only
the good parts (which in my mind is *just* a drawing surface, can a canvas
or SVG responsive widget) a small scripting language (say Lua or JS) and
a communication method (say JSON) and transport mechanism (say TCP)

This (of course) is what we do not do :-) - instead everything that has ever
seen the light of day is bundled into the browser and the parts cannot be
easily separated.

Cheers

/Joe


On Wed, Jul 26, 2017 at 10:20 PM, Albin Stigö <> wrote:
> Hi Joe,
>
> Nice research! Interesting list of software.
>
> I've used a lot of GUI libraries. My favorite is Cocoa/Xcode and QT is
> pretty good too.
>
> I like interface builders because you get instant visual feedback.
> Also IMHO the tricky part is not the initial layout of widgets but how
> to handle resizing. Interface builder in Xcode solves this with
> constraints. They have a learning curve but it works pretty well. For
> serious work you also have to consider i18n.
>
> Cocoa is good because you can build interfaces both programmatically
> and with interface builder, and you can combine the two approaches.
> Interface builder just serializes the object graph so they are
> essentially the same.
>
> I'd also say that a binding mechanism is essential to avoiding a lot
> of boilerplate code to keep the GUI updated. Cocoa has bindings (on
> osx) that's based on key value observing on (ios and osx). QT has
> signals and slots.
>
>
> --Albin
>
>
> On Wed, Jul 26, 2017 at 7:45 PM, Joe Armstrong <> wrote:
>> More on my search for a good (understandable) GUI engine...
>>
>> I've spent the last few weeks botanising through various
>> GUI/graphics construction kits - and goodness what a mess.
>>
>> I thought I'd share some of my experiences and see if
>> it resonates with anybody.
>>
>> 1) Gui building is an (almost) total mess - I say almost because
>>    there is some good software around - but the good stuff tends to be
>>    experimental, undocumented and difficult to use.
>>
>> 2) The most popular frameworks are bloated, difficult to use and
>>    impossible to understand without significant effort.
>>
>> 3) wxWidgets and the Erlang port wxErlang is usable - but the
>>    documentation assumes you are familiar with the wxWidgets way
>>    of doing things and with OO callback programming - which is
>>    *very* Un-Erlang way of thinking
>>
>> 4) The use of interface builders (Xcode, etc.) is a symptom of
>>    problem. GUI codes gets so messy that it is virtually impossible
>>    to write "by hand" - so enter the GUI builder - this is basically
>>    giving up on the idea that GUIs can be written in a clear and
>>    simple manner by hand.
>>
>> 5) In the late 1970 - mid 80's there were several GUI languages
>>    and systems that were easy to use and easy to program. For
>>    example Smalltalk, TCL, Visual basic, Borland Turbo Graphics
>>
>> Is there any good stuff around today?
>>
>> Surprisingly the answer is yes - but the code is difficult to find
>> not supported and not mainstream.
>>
>> First a couple of papers that you might find interesting:
>>
>>    + http://www.eugenkiss.com/projects/thesis.pdf
>>      and https://github.com/eugenkiss/7guis/wiki
>>
>>     The author solves 7 different problems with a number of different
>>     GUI's
>>
>>    + http://blog.johnnovak.net/2016/05/29/cross-platform-gui-trainwreck-2016-edition/
>>
>>    A great read - This blog has a lot of good information about the techniques
>>    used to build several state of the art GUIs (for example Reaper,
>> Blender, Light table)
>>    so If you've every wondered how fancy GUIs work this article gives
>> several clues.
>>
>>    It also has the rather nice example of a GUI written using the
>> Electron Framework
>>    that made an 189 MB executable to bang up a window with a small number of
>>    controls in it.
>>
>>    There's a list of references in one of the comments to this blog that
>>    lead to several interesting *small'ish GUIs'
>>
>> Good stuff
>>
>>    I did find some good software and some potentially very good software.
>>    My top picks are as follows:
>>
>>    http://inscore.sourceforge.net/
>>
>>       This is my favorite from an architectural POV.
>>       It is controlled entirely by sending it messages.
>>       Not a single callback to be seen
>>
>>    https://github.com/andlabs/libui
>>
>>       This looks very promising - it's a cross platform adaption layer
>>       with a C interface - I've only build it on a Mac but
>>       the adaption layer looks pretty easy to use. There's a C interface
>>       that could be adapted to Erlang.
>>
>>       There are very few examples
>> https://github.com/andlabs/ui/wiki/Getting-Started
>>       has a go example - but if you download and build the system the
>>       C examples are easy to follow.
>>
>>    http://www.red-lang.org/
>>
>>       Is amazing - Red is a language inspired by REBOL.
>>
>>       REBOL never achieved much popularity - perhaps Red will.
>>       Once you've see red you'll wonder why you program in anything else
>>       (there are good reasons - but for simply desktop apps Red is great).
>>
>>    https://github.com/wjakob/nanogui
>>
>>       Restores my faith in programming - it's small and built on top
>>       of https://github.com/memononen/NanoVG
>>
>>       NanoVG is basically a canvas type interface to OpenGL
>>
>>       Reading the NanoGui code made me wonder if the best way to make
>>       a GUI for erlang would be to use OpenGL for the low-level stuff
>>       and do all the rest in Erlang.
>>
>>       Buttons etc. are pretty easy to define as processes which I believe
>>       is the way http://www.wings3d.com/ did things.
>>
>> The future
>>
>> I'm still undecided - one of more of the following seem attractive
>>
>>     1) wxErlang - it works *but* it's big and ugly and has a nasty
>>        programming model
>>     2) An interface to Red would be great - but red is pretty unknown
>>     3) libui looks promising - anybody interested in this?
>>     4) the nanogui/NanoVG track looks good - anything with nano in the
>>        name has my vote
>>     5) The inscore architecture rules - NO CALLBACKS - Yea
>>
>> Verily verily I say unto you - "useth not the callback, even though
>> they that useth the callback are ignited with a great passion and
>> extol the virtues of the callback - for therein lies the madness
>> that do come when the callback faileth for reasons not comprehended'
>>
>> Thus it is writ.
>>
>> Cheers
>>
>> /Joe
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