Unbreak audio build on DragonFly

[jbeich]

DragonFly supports wlroots and has fork of FreeBSD Ports, so may inherit wl-screenrec package recipe. Currently, not listed platforms fail to build:

error[E0432]: unresolved imports `platform`, `crate::Args`
  --> src/main.rs:91:5
   |
91 | use platform::*;
   |     ^^^^^^^^ use of undeclared crate or module `platform`
   |
  ::: src/audio.rs:22:30
   |
22 | use crate::{fifo::AudioFifo, Args};
   |                              ^^^^

error[E0425]: cannot find value `DEFAULT_AUDIO_CAPTURE_DEVICE` in this scope
   --> src/main.rs:163:36
    |
163 |     #[clap(long, default_value_t = DEFAULT_AUDIO_CAPTURE_DEVICE.to_string(), help = AUDIO_DEVICE_HELP)]
    |                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not found in this scope

error[E0425]: cannot find value `AUDIO_DEVICE_HELP` in this scope
   --> src/main.rs:163:85
    |
163 |     #[clap(long, default_value_t = DEFAULT_AUDIO_CAPTURE_DEVICE.to_string(), help = AUDIO_DEVICE_HELP)]
    |                                                                                     ^^^^^^^^^^^^^^^^^ not found in this scope

error[E0425]: cannot find value `DEFAULT_AUDIO_BACKEND` in this scope
   --> src/main.rs:166:36
    |
166 |     #[clap(long, default_value_t = DEFAULT_AUDIO_BACKEND.to_string(), help = "which ffmpeg audio capture backend (see https://ff...
    |                                    ^^^^^^^^^^^^^^^^^^^^^ not found in this scope

error[E0425]: cannot find value `DEFAULT_AUDIO_BACKEND` in this scope
    --> src/main.rs:1587:45
     |
1587 |     if !args.audio && args.audio_backend != DEFAULT_AUDIO_BACKEND {
     |                                             ^^^^^^^^^^^^^^^^^^^^^ not found in this scope

error[E0425]: cannot find value `DEFAULT_AUDIO_CAPTURE_DEVICE` in this scope
    --> src/main.rs:1590:44
     |
1590 |     if !args.audio && args.audio_device != DEFAULT_AUDIO_CAPTURE_DEVICE {
     |                                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not found in this scope

Note, pulse can be made as a fallback but none of BSDs have FFmpeg built with PulseAudio enabled by default. Worse, PulseAudio is broken on DragonFly and discouraged on OpenBSD.

[russelltg]

Currently there is no fallback anyways, but I'm pretty sure if you did get a ffmpeg built with pulse and passed pulse to --audio-backend it would work fine. Anyways, LGTM--cannot test on dragonfly but happy to accept PR's so long they are not hacks.

[jbeich]

Oops, forgot to test against typos:

error: expected `;`, found keyword `pub`
  --> src/main.rs:88:97
   |
88 |         "which audio device to record from. list devices with `cat /dev/sndstat` (pcmN -> dspN)"
   |                                                                                                 ^ help: add `;` here
89 |     pub const DEFAULT_AUDIO_BACKEND: &str = "oss";
   |     --- unexpected token

[russelltg]

Yep--pushed a fix for that. I'll get a simple cargo check CI pipeline up at some point so it's easier to accept contributions (you may have noticed--you're the first ;) )