feat: override reaper to add PIPEWIRE_LATENCY for very low latency

modules/linux/audio-prod/default.nix

@@ -35,9 +35,50 @@ in
         yabridgectl
         alsa-scarlett-gui
       ])
-      ++ (lib.optionals config.liminalOS.config.allowUnfree [
-        pkgs.reaper
-      ])
+      ++ (lib.optionals config.liminalOS.config.allowUnfree (
+        with pkgs;
+        [
+          (reaper.overrideAttrs (
+            finalAttrs: prevAttrs: {
+              installPhase = ''
+                runHook preInstall
+
+                HOME="$out/share" XDG_DATA_HOME="$out/share" ./install-reaper.sh \
+                  --install $out/opt \
+                  --integrate-user-desktop
+                rm $out/opt/REAPER/uninstall-reaper.sh
+
+                # Dynamic loading of plugin dependencies does not adhere to rpath of
+                # reaper executable that gets modified with runtimeDependencies.
+                # Patching each plugin with DT_NEEDED is cumbersome and requires
+                # hardcoding of API versions of each dependency.
+                # Setting the rpath of the plugin shared object files does not
+                # seem to have an effect for some plugins.
+                # We opt for wrapping the executable with LD_LIBRARY_PATH prefix.
+                # Note that libcurl and libxml2 are needed for ReaPack to run.
+                wrapProgram $out/opt/REAPER/reaper \
+                  --prefix LD_LIBRARY_PATH : "${
+                    lib.makeLibraryPath [
+                      curl
+                      lame
+                      libxml2
+                      ffmpeg
+                      vlc
+                      xdotool
+                      stdenv.cc.cc
+                    ]
+                  }" \
+                  --prefix PIPEWIRE_LATENCY : "128/48000"
+
+                mkdir $out/bin
+                ln -s $out/opt/REAPER/reaper $out/bin/
+
+                runHook postInstall
+              '';
+            }
+          ))
+        ]
+      ))
     );
 
     musnix.enable = cfg.enable;