Re: [Gtk2hs-users] Help me binding VTE library.

[Axel S. <Axe...@en...>]

Hi Andy,

sorry for being so unreliable in answering. I of course welcome any  
contributions and people who try to contribute!

On Sep 16, 2009, at 16:45, Andy Stewart wrote:
>
> When i compile Vte.hs file, i got below error:
>
>     Vte.chs:67:89:
>         Couldn't match expected type `Widget' against inferred type  
> `()'
>           Expected type: IO (Ptr Widget)
>           Inferred type: IO (Ptr ())
>         In the second argument of `($)', namely `vte_terminal_new'
>         In the second argument of `($)', namely
>             `liftM (castPtr :: Ptr Widget -> Ptr Terminal) $  
> vte_terminal_new'
>
> for binding code:
>
>     terminalNew :: IO Terminal
>     terminalNew =
>         makeNewObject mkTerminal $ liftM (castPtr :: Ptr Widget ->  
> Ptr Terminal) $ {#call unsafe terminal_new#}
>
> In C code, fucntion `GtkWidget *vte_terminal_new(void);' return `IO  
> (Ptr
> Widget), then i use castPtr transform (Ptr Widget) to (Ptr Terminal),
> right?

You need to say

{#import Gtk.Graphics.UI.Types#}

in your import list. This will be parsed by c2hs and inform it that  
it should read the declarations in the corresponding .chi files. Then  
it will know that the Widget* type in the C header file should be  
translated into a Ptr Widget.

Btw, you only need to say castPtr, you don't have to give it a full  
type signature.

Cheers,
Axel.