Re: [Vala] LADSPA bindings

[Aaron Andersen <aaron fosslib net>]

Hi Victor,

Thank you for pointing that out. After reading the documentation for  
that function I believe the best way to bind it would be like so:

    [CCode (cname = "LADSPA_Connect_Port_Function", has_target = false)]
    public delegate void ConnectPortFunc(Handle instance, ulong port,  
[CCode (array_length = false, array_null_terminated = true)] Data[]  
data);

You could then use the function like so:

    // in the case of a single value
    Data[] data = { 1.0f };
    desc.connect_port(handle, 0, data);

    // in the case of multiple values
    Data[] data = { 1.0f, 2.0f, 3.0f };
    desc.connect_port(handle, 0, data);

Please consider contributing this vapi file to the vala extra vapis  
repository.

Thank you,
Aaron

Quoting Victor Aurélio Santos <victoraur santos gmail com>:

> Thank you very much, Aaron
>
> There's only a thing to change, in the connect_port delegate
> DataLocation is a pointer to a float not a float, but changing to
> "Data?" solved.
>
> 2016-09-13 14:19 GMT-03:00 Aaron Andersen <aaron fosslib net>:
> > Hello Victor,
> >
> > You have chosen one of the more difficult C libraries to bind to Vala. The
> > way this library is setup so contrary to the GObject way of doing things it
> > is certainly an edge case.
> >
> > Unfortunately this library requires a small C header "helper" file to
> > accompany your vapi. The main reason for this is that Vala doesn't deal with
> > unnamed function pointers.
> >
> > I've gone ahead and created ladspa.vapi, ladspa-vala.h (a C header "helper"
> > file to make Vala work with the ladspa library), and main.vala (a test
> > program I used to ensure the vapi was correct).
> >
> > main.vala - http://pastebin.com/VF9AXrLY
> > ladspa.vapi - http://pastebin.com/WeaKPHnc
> > ladspa-vala.h - http://pastebin.com/GB4kPzw1
> >
> > I placed all of these 3 files into a single directory and then ran this
> > command to compile:
> >
> > valac --pkg ladspa --vapidir . main.vala --save-temps -X -L/usr/lib/ladspa/
> > -X -l:amp.so -X -I.
> >
> > and this command to run the program:
> >
> > LD_LIBRARY_PATH=/usr/lib/ladspa/ ./main
> >
> > From reading the documentation I understand that the ladspa framework
> > intends for the user to dynamically load plugins via dlopen but I hope you
> > get the idea from the example.
> >
> > Please don't hesitate to ask any questions about this code.
> >
> > Thank you,
> > Aaron
> >
> > Quoting Al Thomas <astavale yahoo co uk>:
> >
> > > > ----- Original Message -----
> > > > From: Victor Aurélio Santos <victoraur santos gmail com>
> > > > Sent: Tuesday, 13 September 2016, 15:55
> > > > Subject: Re: [Vala] LADSPA bindings
> > >
> > >
> > > > Now...
> > >
> > >
> > > > [CCode (cname = "connect_port", has_target = false)]
> > > >     public delegate void DescriptorConnectPort(Handle? instance, ulong
> > > > port, ref double dataLocation);
> > >
> > >
> > > > results in:
> > > > src/CompressorBackend.c: In function ‘ajami_compressor_backend_connect’:
> > > > src/CompressorBackend.c:674:2: error: unknown type name ‘connect_port’
> > > >  connect_port _tmp2_ = NULL;
> > >
> > >
> > >
> > > I presume there's no typedef for it then. Instead try:
> > >
> > > [CCode (lower_case_cprefix = "", has_target = false)]
> > > public delegate void ConnectPort(Handle? instance, ulong
> > > port, ref double dataLocation);
> > >
> > > The lower_case_cprefix should remove the default namespace prefix
> > > and then ConnectPort will be converted to connect_port in C.
> > >
> > > That's my interpretation of the last paragraph of:
> > > https://wiki.gnome.org/Projects/Vala/LegacyBindings#Delegates
> > >
> > > If that doesn't work, I'm not sure what else to suggest. The paragraph
> > > could
> > > mean include an empty cname, e.g.
> > >
> > >
> > > [CCode (cname = "", has_target = false)]
> > > public delegate void DescriptorConnectPort(Handle? instance, ulong
> > > port, ref double dataLocation);
> > >
> > >
> > > Use the --ccode switch with valac to get the C code produced. Look at the
> > > code and tweak it until it works then work back to the VAPI. You can use
> > > valac to compile C. Just use valac --pkg xyz my_c_file.c
> > > _______________________________________________
> > > vala-list mailing list
> > > vala-list gnome org
> > > https://mail.gnome.org/mailman/listinfo/vala-list
>
>
>
> --
> Victor Aurélio Santos