[Haskell-cafe] Idea for a very simple GUI llibrary

[Martin DeMello]

Has there been "real world" adoption of any of these, in the shape of
a moderately complex end-user application that is not just a library
demo?

martin

On Mon, Nov 23, 2009 at 8:48 AM, Keith Holman <holmak at gmail.com> wrote:
> You should also check out Fudgets and "Tangible Functional
> Programming." Fudgets is a really old Haskell UI library concept;
> Tangible FP is a recent Google talk about a UI library inspired by
> Haskell types.
>
> 2009/11/22 Luke Palmer <lrpalmer at gmail.com>:
>> Nice idea.  I will try it if you write runGUI :-)
>>
>> This is an imperative style library.  For more Haskellian GUI library
>> ideas, see Fruit (http://www.haskell.org/fruit/) and TVs
>> (http://www.haskell.org/haskellwiki/TV).  They may not pass the
>> "builds" constraint :-P
>>
>> Luke
>>
>> 2009/11/22 Maurí­cio CA <mauricio.antunes at gmail.com>:
>>> Hi,
>>>
>>> Here is a sketch for a library with these properties:
>>>
>>> -> Easy to test. All Haskell code can be tested in a text
>>> terminal. Also, testing code that uses the library can also be
>>> done without using a GUI.
>>>
>>> -> Extremely easy to document and use.
>>>
>>> -> Not even close to Gtk2hs power, but enough for small
>>> applications.
>>>
>>> -> Could be the first GUI to build on hackage :)
>>>
>>> What we need is:
>>>
>>> -> MyState. A user suplied type for application state.
>>>
>>> -> WidId. A user suplied type for widget identifiers.
>>>
>>> -> Gui wi. A type capable of describing an interface with all of
>>> its state. It's an instance of Eq.
>>>
>>> -> Event wi. A type for events.
>>>
>>> -> Prop. A type for properties than can related to a WidId.
>>>
>>> Running an application would be like this:
>>>
>>> main = runGUI
>>>        initState  -- An initial MyState.
>>>        event      -- :: MyState -> DiffTime -> Event WidId -> MyState
>>>        props      -- :: WidId -> [Prop]
>>>        action     -- :: MyState -> DiffTime -> IO (Maybe (MyState,Gui
>>> WidId))
>>>        timeout    -- :: DiffTime
>>>
>>> DiffTime parameters for callbacks are always the time elapsed
>>> since application started.
>>>
>>> From initState and event, the implementation of runGUI can save a
>>> state that optionally changes with time.
>>>
>>> From props, it can get details on what to present in widgets
>>> associated with a WidId (selected state, picture to draw etc.).
>>>
>>> action presents a chance for using IO, and optionally change state
>>> and GUI description.
>>>
>>> timeout is the maximum time runGUI implementation is allowed to
>>> wait between calls to action.
>>>
>>> Examples for those types:
>>>
>>> newtype MyState = {
>>>    lastUpdate :: DiffTime,
>>>    builtGui :: Bool,
>>>    earthCoordinates :: (Double,Double),
>>>    map :: SVG,
>>>    ...
>>>  }
>>>
>>> data WidId = XCoord | YCoord | MapWindow | ReloadButton ...
>>>
>>> data Gui widid = TitleWindow (Gui widid)
>>>      | Tabs [(String,Gui widid)]
>>>      | PressButton String widid
>>>      | Selection [String] widid
>>>      | ...
>>>  deriving Eq
>>>   {-
>>>      Eq is needed by runGUI to detect if GUI has
>>>      changed after the last call to action.
>>>   -}
>>>
>>> data Event widid = ButtonPressed widid
>>>      | FileSelected String widid
>>>      | OptionSelected String widid
>>>      | ...
>>>
>>> data Prop widid = Active Bool
>>>      | Text String
>>>      | Draw SVG
>>>      | ...
>>>
>>> I believe this can represent most kinds of simple applications,
>>> and be efficient enough for practical use.
>>>
>>> It's interesting that all of this can be designed, implemented and
>>> tested independent of runGUI implementation. Actually, if you want
>>> a pet project and want to write and design the Haskell part, I may
>>> probably be able to write runGUI for you :)
>>>
>>> Best,
>>> Maurício
>>>
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