Hi,
I figured that I would announce a library that I have been working on for a
while now.
It's called Hafni, and it's a swing wrapper. Why another swing wrapper?
I wanted to solve the following problems:
1. There are a lot of boilerplate code needed.
2. Changes made to content is not very functional.
3. Changing content is (sometimes) annoyingly hard.
To solve these problems, I looked into the very functional world of Haskell
and found something called Functional reactive programming (FRP)[1][2] which
has been used to solve problem 2 in gui programming for Haskell. To be able
to program FRP, the datatype "arrow" was created (or maybe the other way
around), and this is what Hafni uses. I wont go into detail here since it is
not very easy to explain in a short mail, and there are a lot of resources
out there on the subject (see the links).
To be honest, when I first started programming on Hafni, I didn't know that
there existed other swing wrappers for java (I guess I also wanted to try
this myself, which meant that I didn't really search it out), but since they
do exist, lets compare Hafni to the two I have seen on this mailing list:
seesaw [3] and GUIFTW [4].
1. Hafni is strictly a swing wrapper and does not claim to be anything else.
Seesaw - aims to provide a ui library, "It happens to be built on Swing".
GUIFTW - "It's not tied to any GUI toolkit but instead front-ends for
each can be written easily."
2. Hafni has facilities, but is not really interested in exactly how
components look.
Seesaw - Doesn't really express an opinion about this, but seems to have
a lot of facilities for making components look a certain way.
GUIFTW - "Style it in a CSS fashion"
3. When events happen, Hafni uses the "Event" and "arrow" datatypes to make
things happen while both
seesaw and GUIFTW uses something that looks like
the standard java event function(s). It should be noted that Hafni
event/arrows
behaves exactly like corresponding for seesaw and GUIFTW if no changes is
made to content.
The reason of 2 (which, in a way, leads to 3) is that when I wrote swing
code manually, the parts
that I were most annoyed with weren't to make things look as I wanted them,
it was changing them.
I haven't really looked into it exactly (or tried it), but it looks like
seesaw and Hafni can be combined
since seesaw deals directly with java objects (the "config!" function is
especially interesting) [5].
I would like to end this mail with an example of Hafni. This example is the
same as in the Hafni readme.
(frame :content (comp-and-events (button :text "*")
:act (flow (output-arr this :text) >>>
(arr #(str % "*")) >>>
(input-arr this :text)))
:size 200 200 :dont_exit_on_close)
As it's already explained in the readme, let's look at the most interesting
part:
(flow (output-arr this :text) >>> (arr #(str % "*")) >>> (input-arr this :text))
This code snippet says that the current text of the button created with
(button :text "*") should "flow" to
the function #(str % "*") which adds a "*" to the text, which should flow to
the text of that same button.
The result of this is that when the button is pressed, the text of that
button is changed as follows:
"*"
"**"
"***"
"****"
etc ...
And finally, the link to Hafni: https://github.com/odyssomay/Hafni
___________________
I really hope that someone finds this project interesting, and at best even
useful. ;)
Questions, comments, ideas, critique?
Jonathan
1. http://en.wikipedia.org/wiki/Functional_reactive_programming
2. http://www.haskell.org/haskellwiki/Functional_Reactive_Programming
3. https://github.com/daveray/seesaw
4. https://github.com/santamon/GUIFTW
5. http://daveray.github.com/seesaw/seesaw.core-api.html#seesaw.core/config!
Additional links:
http://www.haskell.org/haskellwiki/Arrow
http://en.wikibooks.org/wiki/Haskell/Understanding_arrows
http://www.haskell.org/arrows/
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