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 wrote:

"Jefferson Heard" 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.

-- (c) this sig last receiving data processing entity. Inspect headers for past copyright information. All rights reserved. Unauthorised copying, hiring, renting, public performance and/or broadcasting of this signature prohibited.

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

-- 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

Jefferson Heard wrote:

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]

import Foreign.C import Foreign.Ptr import Foreign.Marshal.Array import Control.Applicative((<$>)) oneway :: Ptr CFloat -> IO [Float] oneway p = map real2Frac <$> peekArray 4 p the other way you would probably want withArray, but I think this is the way you need?

Sorry, it's "realToFrac". Typo! Jefferson Heard wrote:

Exactly. thanks!

On Fri, Jun 20, 2008 at 4:26 PM, Jules Bean mailto:jules@jellybean.co.uk> wrote:

Jefferson Heard wrote:

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]

import Foreign.C import Foreign.Ptr import Foreign.Marshal.Array

import Control.Applicative((<$>))

oneway :: Ptr CFloat -> IO [Float] oneway p = map real2Frac <$> peekArray 4 p

the other way you would probably want withArray, but I think this is the way you need?

-- 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

------------------------------------------------------------------------

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe