Add support for Direct RetroArch Game forwarding

README.md

@@ -12,8 +12,6 @@ The exefs ROM used is the one by [meliodas2255] which was based on or inspired b
 Both ROMs are supported as they use the same romfs structure for specifying which NRO to load from the microSD card.
 Simply replace the assets in the `/assets/exefs` folder with the [original ROM][ROM]'s exefs files.
 
-**Note**: Direct RetroArch game forwarding is not yet supported.
-
 ## Changes
 
 1. The script was completely rewritten in Python.
@@ -37,7 +35,7 @@ Simply replace the assets in the `/assets/exefs` folder with the [original ROM][
 3. Place your `prod.keys` at the root of the project folder or at `%USERPROFILE/.switch/prod.keys`. Make sure it's
    up-to-date for the firmware version you're switch is on. You can get this file using [Lockpick_RCM].
 4. Run `pip install nton`. If you see any warnings about a path not being in your PATH environment variable, add it
-   or you wont be able to run `nton`.
+   or you won't be able to run `nton`.
 
   [ImageMagick]: <https://imagemagick.org/script/download.php>
   [winget]: <https://winget.run>
@@ -60,14 +58,25 @@ E.g., to make a forwarder for the Homebrew Menu that's on your Switch's microSD
 
 Take a look at `nton build --help` for advanced usage like changing the Icon, Title Name, and so on.
 
+### Direct RetroArch Game forwarding
+
+Use a RetroArch Game Core as the NRO path and provide the path to the ROM on your Switch's microSD card with `--rom`.  
+This will then load the Core directly under RetroArch and provide the path to the ROM as a startup argument to the
+RetroArch Core.
+
+Note:
+
+- You must use a path to a RetroArch Game Core NRO, not the path to the RetroArch NRO itself.
+- Do not move, delete, or rename the ROM or the Core NRO files that are on your microSD card, or it will break.
+
 ## To-do
 
 - [X] Rewrite as a Python script to heavily improve the user experience and code.
 - [X] Combine the Drive letter and Path arguments and manually split them when they need to be separate instead.
 - [X] Automate name and publisher by extracting from the extracted `control.nacp`.
 - [X] Force enable video capture and screenshots in the extracted `control.nacp`.
+- [x] Add support for direct RetroArch Game Forwarding.
 - [ ] Force disable save data allocation. Fixed in [v3.3.5 of Nro2NSP](https://github.com/Root-MtX/Nro2Nsp/releases/tag/3.3.5).
-- [ ] Add support for direct RetroArch Game Forwarding.
 - [ ] Maybe a new GUI one day, and let you override the icons and such?
 
 ## Troubleshooting

nton/main.py

@@ -40,7 +40,15 @@ def main(version: bool, debug: bool) -> None:
 @click.option("-p", "--publisher", type=str, default=None, help="Title Publisher.")
 @click.option("-i", "--icon", type=Path, default=None, help="Title Icon (256x256px recommended, supports any image).")
 @click.option("--id", "id_", type=str, default=None, help="Title ID.")
-def build(path: Path, name: str | None, publisher: str | None, icon: Path | None, id_: str | None) -> int:
+@click.option("--rom", type=Path, default=None, help="ROM path for Direct RetroArch Game Forwarding.")
+def build(
+    path: Path,
+    name: str | None,
+    publisher: str | None,
+    icon: Path | None,
+    id_: str | None,
+    rom: Path | None
+) -> int:
     """
     Build an NSP that loads an NRO on the Switch's microSD card.
 
@@ -53,7 +61,8 @@ def build(path: Path, name: str | None, publisher: str | None, icon: Path | None
             resolution. A 256x256px image is recommended.
         id_: Set a specific Title ID, otherwise a Random Title ID is used. There's a miniscule chance it could get the
             same Title ID as another installed Title, but it's so miniscule you shouldn't realistically worry about it.
-
+        rom: Path to a ROM file to create a forwarder that boots directly into the game using RetroArch. The NRO path
+            must be to a RetroArch Core.
     """
     log = logging.getLogger("build")
     log.info("Building!")
@@ -88,6 +97,15 @@ def build(path: Path, name: str | None, publisher: str | None, icon: Path | None
     else:
         id_ = "01%s000" % os.urandom(6).hex()[:-1]
 
+    if rom:
+        if not rom.is_file():
+            log.error(f"The ROM path \"{rom}\" does not exist, or is not a file.")
+            return 1
+        if not str(path).lower().startswith(f"{path.drive.lower()}:/retroarch/cores/"):
+            log.error(f"Setting a ROM path for the forwarder requires the NRO path to be to a RetroArch Core.")
+            log.error(f"Make sure you set it to a RetroArch Core and not to RetroArch itself or any other NRO.")
+            return 1
+
     log.info(f"Title ID: %s", id_)
 
     build_dir = Directories.temp / id_
@@ -179,9 +197,13 @@ def build(path: Path, name: str | None, publisher: str | None, icon: Path | None
             log.critical(f"Failed to convert and strip the Icon, {e.output} [{e.returncode}]")
             return 2
 
-        sdmc_path = f"sdmc:{str(path.resolve().absolute()).split(':', maxsplit=1)[1]}"
+        next_nro_path = str(path.resolve().absolute()).replace(f"{path.drive}:/", "sdmc:/")
-        next_argv_file.write_text(sdmc_path)
+        next_nro_path_file.write_text(next_nro_path)
-        next_nro_path_file.write_text(sdmc_path)
+
+        next_argv = next_nro_path
+        if rom:
+            next_argv += " " + str(rom.resolve().absolute()).replace(f"{rom.drive}:/", "sdmc:/")
+        next_argv_file.write_text(next_argv)
 
         # only make this directory at this point because we have a high chance of success
         Directories.output.mkdir(parents=True, exist_ok=True)