Re: [Vala] LADSPA bindings



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
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-- 
Victor Aurélio Santos


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