sysaudio: rewrite in zig

[alichraghi]

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Closes #625

blockers:

• add audio sdk hexops-graveyard/sdk-linux-x86_64#5
• add audio sdk hexops-graveyard/sdk-linux-aarch64#3

[alichraghi]

ready for review. CI failure is because system-sdk must be updated and after that piano example i guess

[kdchambers]

I'm getting a similar error as the Linux CI, only for Jack. Obviously I don't have an appropriate audio back-end installed (Pipewire), but perhaps this could be caught at comptime and return a nicer error. I guess this should be fixed once the audio sdk is updated?

As for Context depending on itself, that seems real unfortunately. Maybe just a limitation in Zig that needs to be worked around for now. Similar to ziglang/zig#131

const c = @cImport(@cInclude("jack/jack.h"));
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
referenced by:
    Player: libs/sysaudio/src/jack.zig:175:14
    Player: libs/sysaudio/src/jack.zig:169:20
    remaining reference traces hidden; use '-freference-trace' to see all reference traces

/home/keith/github/wrkdir/mach_ali/zig-cache/o/56e0d4bbaaf593154d693621f05d82e3/cimport.h:1:10: error: 'jack/jack.h' file not found
#include <jack/jack.h>
         ^
libs/sysaudio/src/jack.zig:7:21: error: struct 'jack.Context' depends on itself
pub const Context = struct {
                    ^~~~~~
libs/sysaudio/src/jack.zig:7:21: error: struct 'jack.Context' depends on itself
pub const Context = struct {
                    ^~~~~~
libs/sysaudio/src/jack.zig:7:21: error: struct 'jack.Context' depends on itself
pub const Context = struct {
                    ^~~~~~
libs/sysaudio/src/main.zig:104:20: error: struct 'main.Player' depends on itself
pub const Player = struct {
                   ^~~~~~
libs/sysaudio/src/jack.zig:7:21: error: struct 'jack.Context' depends on itself
pub const Context = struct {
                    ^~~~~~
libs/sysaudio/src/jack.zig:7:21: error: struct 'jack.Context' depends on itself
pub const Context = struct {
                    ^~~~~~
libs/sysaudio/src/backends.zig:28:15: error: union 'backends.BackendPlayer__union_4717' depends on itself
    .linux => union(enum) {
              ^~~~~
libs/sysaudio/src/jack.zig:7:21: error: struct 'jack.Context' depends on itself
pub const Context = struct {
                    ^~~~~~
libs/sysaudio/src/backends.zig:28:15: error: union 'backends.BackendPlayer__union_4717' depends on itself
    .linux => union(enum) {
              ^~~~~
libs/sysaudio/src/jack.zig:7:21: error: struct 'jack.Context' depends on itself
pub const Context = struct {
                    ^~~~~~
libs/sysaudio/src/backends.zig:28:15: error: union 'backends.BackendPlayer__union_4717' depends on itself
    .linux => union(enum) {
              ^~~~~
libs/sysaudio/src/backends.zig:28:15: error: union 'backends.BackendPlayer__union_4717' depends on itself
    .linux => union(enum) {
              ^~~~~
libs/sysaudio/src/backends.zig:28:15: error: union 'backends.BackendPlayer__union_4717' depends on itself
    .linux => union(enum) {

I also got the following error when cloning recursively:

fatal: No url found for submodule path 'libs/sysaudio/upstream' in .gitmodule

Which I fixed by removing the path git rm --cached libs/sysaudio/upstream

Seeing as this works for all other targets, if it isn't convenient to test on Linux we could merge this (Or put into a new branch) and I'll fix up these minor issues.

[alichraghi]

@kdchambers for now you need to checkout into my SDK PRs i mentioned above.
clone them somewhere and set MACH_SDK_PATH=<the_sdks_dir>
also fixed the git error. thanks
btw i just saw u got the actual reason lol

[emidoots]

Is panic desirable behavior here? Seems like this should be a documented no-op instead maybe.

[emidoots]

Great work on this. I see this as the future so will merge. I think we regress on a few things:

1. macOS is not currently supported
2. Linux requires e.g. pulseaudio and jack to both be installed, since we dynamically link against them. In the future we should make Linux backends use dlopen so that if not installed we can provide a nicer error / just disable the backend which doesn't exist.
3. WebAudio support is removed for now (but is being worked on.)

We'll need to address these in the near future, but for now this is a great step forward.