[Haskell-cafe] Re: Wrapping FTGL in FFI calls

[Jefferson Heard]

Oh, and I should say the function I want to implement is

getFontBBox :: Font -> String -> IO [Float]

I do know how to marhsal/unmarshal the String.  Just not the CFloat array to
Haskell [Float]

On Fri, Jun 20, 2008 at 2:25 PM, Jefferson Heard <
jefferson.r.heard at gmail.com> wrote:

> Well, Achim you were almost exactly correct.  I have a functional function
> interface in about half an hour's worth of work.  I have one question, which
> is how to create a Ptr to four CFloats on the fly, pass them to the bounding
> box functions, and then come back out with a [Float]
>
> My prototype looks like this:
> foreign import ccall unsafe "ftglGetFontBBox" fgetFontBBox :: Font ->
> CString -> Ptr CFloat -> IO ()
>
> the ptr to cfloat should be a float[4], which is modified inside the
> original C function.
>
>
> On Fri, Jun 20, 2008 at 1:16 AM, Achim Schneider <barsoap at web.de> wrote:
>
>> "Jefferson Heard" <jefferson.r.heard at gmail.com> wrote:
>>
>> > I've been looking for awhile now for a simple way to get truetype
>> > fonts into my visualizations so I can abandon the hideous GLUT fonts
>> > and make things that look like they were developed in the 1990s
>> > instead of back in the days of TRON.  I found FTGL, but I'm mostly a
>> > Haskell developer these days, and resent having to go back to C just
>> > to write a simple application.
>> >
>> > So I was wondering if anyone had ever wrapped the FTGL library in
>> > Haskel FFI or whether those out there who are experts on the FFI
>> > think at first glance it should be readily wrappable by a rank
>> > amateur at FFI such as myself.
>> >
>> > http://ftgl.sourceforge.net/docs/html/
>> >
>> Using the FFI is generally straight forward, as long as you can live
>> with using the IO monad and the C code uses objects (well,
>> pointers to structs passed as first argument, where's the
>> difference...).
>>
>> Things only depend on the purity of the C code and how high-level you
>> want your interface to be. In this case, I estimate half an hour if
>> you're a fast typist. That includes the time needed to read the FFI
>> docs.
>>
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>
>
>
> --
> I try to take things like a crow; war and chaos don't always ruin a picnic,
> they just mean you have to be careful what you swallow.
>
> -- Jessica Edwards




-- 
I try to take things like a crow; war and chaos don't always ruin a picnic,
they just mean you have to be careful what you swallow.

-- Jessica Edwards
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