Re: [Vala] Using a C library

[yannick inizan <inizan yannick gmail com>]

1) You must write a vapi for libspotify, then call it with "valac main.vala
--pkg libspotify --vapidir=/path/to/vapi"
2) sp_error doesn't exist, in your code I see "Spotify.Error" ;)

here a small example of vapi for libspotify ;) :
http://pastebin.com/XEEVUKMt

2015-04-18 20:22 GMT+02:00 Justin Brown <justin brown fandingo org>:

> Hello,
>
> I'm just getting started with Vala, and I've run into a snag.
> Unfortunately, even after crawling the internet for several hours trying to
> find a solution, I can't seem to find any help. Sorry to ask such a basic
> question.
>
> I'm trying to wrap the proprietary libspotify C library. I've found this
> guide (https://wiki.gnome.org/Projects/Vala/LegacyBindings), which is
> really helping with wrapping types and methods. Combined with the Vala
> tutorial, I've written a little bit of Vala code to start testing.
>
> Unfortunately, I can't seem to find any information about how to compile my
> program so far. I come from a Python background, so compiling and
> including/importing other files is generally very simple, but I can't
> figure out how to do it with Vala. I've even tried looking through C# and
> Mono documentation, but that didn't seem useful.
>
> My package manager has a libspotify package, so I installed it, which gives
> me /usr/include/libspotify/api.h and /usr/lib64/libspotify.so. For my
> program, I currently have two files fandingo.vala (main program) and
> spotify.vala (classes for wrapping libspotify). They are both in the same
> directory.
>
> fandingo.vala is currently extremely simple and just has a class for DBus
> communication (mostly cobbled together from a Vala DBus tutorial):
>
> using Spotify;
>
>
> [DBus (name = "org.fandingo.Fandingo")]
>
> class Fandingo.fandingo : GLib.Object {
>
> private int c;
>
>  public int ping(string m) {
>
> stdout.printf("%s\n", m);
>
> return c++;
>
> }
>
>
> public int ping_with_signal(string m) {
>
> stdout.printf("%s\n", m);
>
> return c++;
>
> }
>
>
> public void ping_err() throws GLib.Error {
>
> throw new FandingoError.SOME_ERROR("Error encountered");
>
> }
>
>
> public int sp_error_code() {
>
> Spotify.Error err = Spotify.Error.OK;
>
> stdout.printf("Error: %s, %d\n", err.to_string(), err);
>
> return err;
>
> }
>
>
> public signal void pong(int count, string msg);
>
> }
>
>
> [DBus (name = "org.fandingo.FandingoError")]
>
> public errordomain FandingoError {
>
> SOME_ERROR
>
> }
>
>
> void on_bus_acquired(DBusConnection conn) {
>
> try {
>
> conn.register_object("/org/fandingo/fandingo", new Fandingo.fandingo());
>
> } catch (IOError e) {
>
> stderr.printf("No registration\n");
>
> }
>
> }
>
>
> void main() {
>
> Bus.own_name (BusType.SESSION, "org.fandingo.Fandingo",
> BusNameOwnerFlags.NONE, on_bus_acquired, () => {}, () => stderr.printf("No
> name\n"));
>
> new MainLoop().run();
>
> }
>
>
>
> spotify.vala is very simple as well, and just wraps the error enum and
> method to get an error string:
>
> namespace Spotify {
>
> [CCode (cname = "sp_error", cprefix = "SP_ERROR_", has_type_id= false)]
>
> public enum Error {
>
> OK,
>
> BAD_API_VERSION,
>
> API_INITIALIZATION_FAILED,
>
> TRACK_NOT_PLAYABLE,
>
>   // truncated
>
>
> [CCode (cname = "sp_error_message")]
>
> private static char* get_string(sp_error err);
>
>
> public string to_string() {
>
> return (string) Error.get_string(this);
>
> }
>
>
> }
>
> }
>
> I'm sure there are some programming errors, but I feel like I can work
> through those if I can just figure out how to tell the compiler to use
> libspotify/api.h.
>
> When I just had fandingo.vala and was doing the DBus testing (without the
> sp_error_code() method), compiling was easy:
>
> valac --pkg gio-2.0 fandingo.vala
>
> I've tried using
>
> valac --pkg gio-2.0 fandingo.vala spotify.vala
>
> But that gives me an error presumably because valac doesn't know how to
> include api.h/libspotify.so.
>
> spotify.vala:44.35-44.42: error: The type name `sp_error' could not be
> found
>                 private static char* get_string(sp_error err);
>
>
>                                                 ^^^^^^^^
>
>
> Compilation failed: 1 error(s), 0 warning(s)
>
> I also tried adding a C-style include to spotify.vala: #include
> <libspotify/api.h>, but that didn't work.
>
> Again, sorry for the basic question, but I can't seem to figure this out.
>
> Thanks,
> Justin
> _______________________________________________
> vala-list mailing list
> vala-list gnome org
> https://mail.gnome.org/mailman/listinfo/vala-list