Re: [Vala] LADSPA bindings

[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
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