Do not use loop to check for launcher

Do not use a loop to sleep until the Steam Runtime
launcher has finished starting up. Instead, create a pipe and pass it to
the underlying `steam-runtime-launcher-service` executable; the
executable will write to it and close it to indicate the launcher has
finished starting up.

After this every subsequent `wine_launch.sh` invocation can assume the
launcher is up instead of checking for the socket in a loop.

This approach was suggested by @smcv on GitHub.

Fixes #231

src/protontricks/data/scripts/bwrap_launcher.sh

@@ -80,6 +80,10 @@ done
 log_info "Following directories will be mounted inside container: ${mount_dirs[*]}"
 log_info "Using temporary directory: $PROTONTRICKS_TEMP_PATH"
 
-exec "$STEAM_RUNTIME_PATH"/run --share-pid --launcher \
+# Protontricks will listen to this file descriptor. Once it's closed,
+# the launcher has finished starting up.
+status_fd="$1"
+
+exec "$STEAM_RUNTIME_PATH"/run --share-pid --launcher --pass-fd "$status_fd" \
 "${mount_params[@]}" -- \
---bus-name="com.github.Matoking.protontricks.App${STEAM_APPID}_${PROTONTRICKS_SESSION_ID}"
+--info-fd "$status_fd" --bus-name="com.github.Matoking.protontricks.App${STEAM_APPID}_${PROTONTRICKS_SESSION_ID}"

src/protontricks/data/scripts/wine_launch.sh

@@ -173,14 +173,6 @@ elif [[ "$PROTONTRICKS_STEAM_RUNTIME" = "bwrap" ]]; then
     # expose the unique host PID.
     bus_name="com.github.Matoking.protontricks.App${STEAM_APPID}_${PROTONTRICKS_SESSION_ID}"
 
-    # Wait until socket is created
-    if ! dbus-send --print-reply --dest=org.freedesktop.DBus  /org/freedesktop/DBus org.freedesktop.DBus.ListNames | grep -q "$bus_name"; then
-        log_info "bwrap-launcher D-Bus object not yet available, waiting..."
-        while ! dbus-send --print-reply --dest=org.freedesktop.DBus  /org/freedesktop/DBus org.freedesktop.DBus.ListNames | grep -q "$bus_name"; do
-            sleep 0.25
-        done
-    fi
-
     # Pass all environment variables to 'steam-runtime-launch-client' except
     # for problematic variables that should be determined by the launch command
     # instead.

src/protontricks/util.py

@@ -474,13 +474,27 @@ def run_command(
                 "Starting bwrap launcher process: %s",
                 str(wine_bin_dir / "bwrap-launcher")
             )
+
+            # TODO: Waiting for launcher to start can be simplified once
+            # ValveSoftware/steam-runtime#593 has been fixed and stdout can
+            # be used instead.
+            launcher_read_fd, launcher_write_fd = os.pipe2(os.O_CLOEXEC)
             launcher_process = _start_process(
-                str(wine_bin_dir / "bwrap-launcher"),
+                [str(wine_bin_dir / "bwrap-launcher"), str(launcher_write_fd)],
                 wait=False,
-                env=wine_environ,
-                stdout=DEVNULL,
+                pass_fds=[launcher_write_fd],
+                env=wine_environ
             )
 
+            # The Steam Runtime launcher service will write to the given
+            # file descriptor and then close it to indicate the launcher is
+            # ready.
+            os.close(launcher_write_fd)
+            with open(launcher_read_fd, "rb") as reader:
+                reader.read()
+            # Launcher has finished starting up once output is returned
+            logger.info("bwrap launcher started")
+
         if start_wineserver:
             logger.info(
                 "Starting wineserver keepalive process: %s",

tests/cli/test_main.py

@@ -166,7 +166,7 @@ def test_run_winetricks_steam_runtime_v2(
 
         # Launcher process was launched to handle launching processes
         # inside the sandbox
-        assert commands[0].args == str(wine_bin_dir / "bwrap-launcher")
+        assert commands[0].args[0] == str(wine_bin_dir / "bwrap-launcher")
 
         # winecfg was run
         command = commands[-1]