# FFDec guide — add Multiplayer button to MainMenu.swf

> **Deprecated:** Use C++ runtime injection instead. See [`MainMenu_Injection.md`](MainMenu_Injection.md). Do not deploy a patched `MainMenu.swf` for Commonwealth Online.

Step-by-step instructions for adding the **Multiplayer** main-menu item using [JPEXS FFDec](https://github.com/jindrapetrik/jpexs-decompiler/releases), without breaking **Settings → Gameplay / Display / Audio**.

This guide is kept for historical reference only.

---

## Before you start

### Restore vanilla SWF

Always patch from the vanilla file, not an old broken copy:

```powershell
.\tools\restore-vanilla-mainmenu.ps1
```

Or manually copy `Interface/MainMenu.swf.vanilla.bak` → `Interface/MainMenu.swf`.

Vanilla size is **61,959 bytes**. If your file is **64 KB+**, it is probably a bad re-import — restore and start again.

### Requirements

- **FFDec** installed
- Game launched via **F4SE** with `CommonwealthOnline.dll` in `Data/F4SE/Plugins/`
- Loose Interface overrides enabled in `%USERPROFILE%/Documents/My Games/Fallout4/Fallout4Custom.ini`:

```ini
[Archive]
bInvalidateOlderFiles=1
```

### Critical rule

| Do | Don't |
|----|--------|
| Edit **individual methods** (double-click method in traits list) | Paste the full `MainMenu.as` export into the class editor |
| Save after each small edit | Use **Import script** on the whole `MainMenu` class |
| Keep SWF ~62–63 KB | Re-export the entire decompiled script |

Full re-import recompiles `RequestOptions` and breaks settings sub-menus. Controls will still work; Gameplay / Display / Audio will crash.

---

## FFDec navigation

1. Open **`Interface/MainMenu.swf`** in FFDec.
2. Left tree: **scripts → MainMenu**.
3. You should see a **traits / members list** (constants, functions).
4. **Double-click a method name** (e.g. `InitList`) to open **only that method** in the editor.
5. After each edit: apply/save the method, then **File → Save** the SWF.

Do **not** use **Edit ActionScript** on the entire `MainMenu` class if FFDec offers a single giant class view — use per-method editing instead.

---

## Summary of changes

| # | Where in FFDec | What |
|---|----------------|------|
| 1 | Class constants | Add `MULTIPLAYER_INDEX` |
| 2 | Method `InitList` | Push Multiplayer row after Load |
| 3 | Method `onMainListItemPress` | Add `case` for Multiplayer |
| 4 | New method `CloseMultiplayerBrowser` | Helper (recommended) |
| 5 | Method `set currentState` | Call close helper when leaving main panel |
| 6 | Method `onMainListItemPress` | Close browser when another item is selected |

Changes **4–6** are recommended so the HTML browser closes immediately when opening Settings, etc. The plugin also hides the browser when `currentState` leaves `MAIN_STATE`, but the SWF hooks make it feel instant.

---

## Change 1 — Add index constant

**FFDec:** `MainMenu` → constants section (near other `*_INDEX` constants)

**Find this block** (search for `INSTALLED_CONTENT_INDEX`):

```actionscript
      private const INSTALLED_CONTENT_INDEX:Number = 14;
      
      private const MAIN_PANEL_BACKGROUND:uint = 0;
```

**Insert between those lines:**

```actionscript
      private const MULTIPLAYER_INDEX:Number = 15;
```

Index `15` is unused in vanilla (highest defined index is `14`).

---

## Change 2 — Add menu row in `InitList`

**FFDec:** `MainMenu` → method **`InitList`**

**Find this block** (search for `"$LOAD"` push — it appears after the `$NEW` block on title screen):

```actionscript
         this.MainPanel_mc.List_mc.entryList.push({
            "text":"$LOAD",
            "disabled":!this.HasRecentSave || !param6,
            "index":this.LOAD_INDEX
         });
         if(param8 == true)
```

**Replace with** (add Multiplayer block between Load and `if(param8 == true)`):

```actionscript
         this.MainPanel_mc.List_mc.entryList.push({
            "text":"$LOAD",
            "disabled":!this.HasRecentSave || !param6,
            "index":this.LOAD_INDEX
         });
         if(!this.PauseMode)
         {
            this.MainPanel_mc.List_mc.entryList.push({
               "text":"Multiplayer",
               "index":this.MULTIPLAYER_INDEX
            });
         }
         if(param8 == true)
```

**Notes:**

- `"Multiplayer"` is a literal label (no `$` prefix). Strings with `$` are looked up in `Interface/Translate_en.txt`.
- `!this.PauseMode` limits the row to the **title screen**, not the in-game pause menu.
- Row appears between **Load** and **Add-ons** (or PS5 transfer if enabled).

---

## Change 3 — Handle click in `onMainListItemPress`

**FFDec:** `MainMenu` → method **`onMainListItemPress`**

**Find this block** (search for `case this.HELP_INDEX:`):

```actionscript
                  break;
               case this.HELP_INDEX:
                  this.StartState(this.HELP_STATE);
                  this.BGSCodeObj.PlayOKSound();
                  break;
```

**Insert immediately before** `case this.HELP_INDEX:`:

```actionscript
                  break;
               case this.MULTIPLAYER_INDEX:
                  this.BGSCodeObj.PlayOKSound();
                  if(root.f4se != null && root.f4se.plugins != null && root.f4se.plugins.commonwealthOnline != null)
                  {
                     root.f4se.plugins.commonwealthOnline.openManager();
                  }
                  break;
               case this.HELP_INDEX:
                  this.StartState(this.HELP_STATE);
                  this.BGSCodeObj.PlayOKSound();
                  break;
```

This calls the C++ API registered by `CommonwealthOnline.dll` (`openManager` → PrismaUI server browser). **F9** still toggles the same browser.

---

## Change 4 — Add `CloseMultiplayerBrowser` method

**FFDec:** `MainMenu` → **add new method** (right-click class → Add script / Add method, or paste near other private helpers like `onMainListItemPress`)

**Add this entire method:**

```actionscript
      private function CloseMultiplayerBrowser() : *
      {
         if(root.f4se != null && root.f4se.plugins != null && root.f4se.plugins.commonwealthOnline != null)
         {
            root.f4se.plugins.commonwealthOnline.closeManager();
         }
      }
```

---

## Change 5 — Close browser in `set currentState`

**FFDec:** `MainMenu` → method **`set currentState`** (may appear as `currentState` setter)

**Find:**

```actionscript
      public function set currentState(param1:String) : *
      {
         this.strCurrentState = param1;
         this.UpdateButtons(param1);
         this.UpdateStateFocus(param1);
      }
```

**Change to:**

```actionscript
      public function set currentState(param1:String) : *
      {
         this.strCurrentState = param1;
         if(param1 != this.MAIN_STATE)
         {
            this.CloseMultiplayerBrowser();
         }
         this.UpdateButtons(param1);
         this.UpdateStateFocus(param1);
      }
```

---

## Change 6 — Close browser when another main-menu item is selected

**FFDec:** `MainMenu` → method **`onMainListItemPress`** (same method as Change 3)

**Find** the start of the `else` branch, after the `while` loop that returns to main state:

```actionscript
            while(this.strCurrentState != this.MAIN_STATE)
            {
               this.onCancelPress(true,false);
            }
            if(this.MainPanel_mc.List_mc.selectedEntry.index == this.CONTINUE_INDEX && this.PauseMode)
```

**Insert between the `while` loop and the `CONTINUE_INDEX` check:**

```actionscript
            while(this.strCurrentState != this.MAIN_STATE)
            {
               this.onCancelPress(true,false);
            }
            if(this.MainPanel_mc.List_mc.selectedEntry.index != this.MULTIPLAYER_INDEX)
            {
               this.CloseMultiplayerBrowser();
            }
            if(this.MainPanel_mc.List_mc.selectedEntry.index == this.CONTINUE_INDEX && this.PauseMode)
```

---

## Save and deploy

1. **File → Save** in FFDec (overwrite `Interface/MainMenu.swf`).
2. Check file size: should be roughly **62,000–63,500 bytes**. If **64,000+**, restore vanilla and redo using **method-only** edits.
3. Copy to game:

   ```
   Fallout 4/Data/Interface/MainMenu.swf
   ```

4. Launch via **F4SE**.

---

## Test checklist

| Step | Expected |
|------|----------|
| Main menu (title screen) | **Multiplayer** appears after **Load** |
| Pause menu → Settings | **No** Multiplayer row |
| Click **Multiplayer** | Server browser opens |
| **Settings → Gameplay** | No crash |
| **Settings → Display** | No crash |
| **Settings → Audio** | No crash |
| **Settings → Controls** | Still works |
| Open Multiplayer, then **Settings** | Browser closes |
| **F9** | Still toggles browser |

---

## Troubleshooting

### Settings sub-menus crash again

You likely re-imported the full class. Run `.\tools\restore-vanilla-mainmenu.ps1` and redo changes **1–6** using **per-method** editing only.

### Multiplayer row missing

- Confirm `bInvalidateOlderFiles=1` in `Fallout4Custom.ini`.
- Confirm loose `Data/Interface/MainMenu.swf` exists and is not overridden by another mod (check MO2 load order).
- Confirm you added the `InitList` block with `if(!this.PauseMode)`.

### Multiplayer row visible but click does nothing

- Launch via **F4SE**, not vanilla exe.
- Confirm `CommonwealthOnline.dll` is loading (check `Documents/My Games/Fallout4/F4SE/CommonwealthOnline.log`).
- Confirm Change **3** (`case this.MULTIPLAYER_INDEX`) is present.

### Button shows `$MULTIPLAYER` or wrong text

Use literal `"Multiplayer"` (no `$`), or add a translation key to `Interface/Translate_en.txt`.

---

## Reference files

| File | Purpose |
|------|---------|
| [`MainMenu.swf.vanilla.bak`](../MainMenu.swf.vanilla.bak) | Untouched vanilla backup |
| [`scripts/MainMenu.as`](scripts/MainMenu.as) | Full decompiled reference — **do not import wholesale** |
| [`PATCH_MainMenu_Multiplayer.md`](PATCH_MainMenu_Multiplayer.md) | Short overview |
| [`../../tools/restore-vanilla-mainmenu.ps1`](../../tools/restore-vanilla-mainmenu.ps1) | Restore vanilla SWF from game BA2 |

Plugin API (already implemented in C++):

- `root.f4se.plugins.commonwealthOnline.openManager()`
- `root.f4se.plugins.commonwealthOnline.closeManager()`