Implement support for OpenMW

Most of the complexity is handled by libloadorder, but it's worth noting that:

- The game path is OpenMW's install path, not Morrowind's
- OpenMW doesn't force master-flagged plugins to load before others
- OpenMW doesn't provide a way to record the load order of inactive plugins
- .omwgame and .omwaddon plugins are equivalent to .esm and .esp respectively, while .omwscripts plugins have a completely different format with none of the metadata that libloot uses.
- OpenMW effectively relies on additional data paths to load Morrowind's (and mods') files, and the last directory listed that contains a given filename is used to load a file with that filename, with the main data path effectively being the first listed.
- I've disabled support for ghosted plugins for OpenMW because it makes the multi-path stuff more confusing and may not provide any benefit.

include/loot/api.h

@@ -98,11 +98,13 @@ LOOT_API bool IsCompatible(const unsigned int major,
  *        The relative or absolute path to the directory containing the
  *        game's executable.
  * @param game_local_path
- *        The relative or absolute path to the game's folder in
- *        `%%LOCALAPPDATA%` or an empty path. If an empty path, the API will
- *        attempt to look up the path that `%%LOCALAPPDATA%` corresponds to.
- *        This parameter is provided so that systems lacking that environmental
- *        variable (eg. Linux) can still use the API.
+ *        The relative or absolute path to the game's local data folder, or an
+ *        empty path. The local data folder is usually in `%%LOCALAPPDATA%`, but
+ *        Morrowind has no local data folder and OpenMW's is in the user's
+ *        My Games folder on Windows and in `$HOME/.config` on Linux. If an
+ *        empty path is provided, the API will attempt to look up the relevant
+ *        local data path, which may fail in some situations (e.g. when running
+ *        libloot natively on Linux for a game other than Morrowind or OpenMW).
  * @returns The new game handle.
  */
 LOOT_API std::unique_ptr<GameInterface> CreateGameHandle(

include/loot/enum/game_type.h

@@ -50,7 +50,9 @@ enum struct GameType : unsigned int {
   /** The Elder Scrolls III: Morrowind */
   tes3,
   /** Starfield */
-  starfield
+  starfield,
+  /** OpenMW */
+  openmw
 };
 }
 

include/loot/game_interface.h

@@ -41,9 +41,11 @@ public:
 
   /**
    * @brief   Gets the currently-set additional data paths.
-   * @details Only Fallout 4 installed from the Microsoft Store is configured
-   *          with any additional data paths by default, as its DLC directories
-   *          are installed outside of the Fallout 4 install path.
+   * @details The following games are configured with additional data paths by
+   *          default:
+   *          - Fallout 4, when installed from the Microsoft Store
+   *          - Starfield
+   *          - OpenMW
    */
   virtual std::vector<std::filesystem::path> GetAdditionalDataPaths() const = 0;
 
@@ -52,8 +54,9 @@ public:
    * @details The additional data paths are used when interacting with the load
    *          order, evaluating conditions and scanning for archives (BSA/BA2
    *          depending on the game). Additional data paths are used in the
-   *          order they are given, and take precedence over the game's main
-   *          data path.
+   *          order they are given (except with OpenMW, which checks them in
+   *          reverse order), and take precedence over the game's main data
+   *          path.
    */
   virtual void SetAdditionalDataPaths(
       const std::vector<std::filesystem::path>& additionalDataPaths) = 0;
@@ -87,9 +90,9 @@ public:
 
   /**
    * @brief Check if a file is a valid plugin.
-   * @details The validity check is not exhaustive: it checks that the file
-   *          extension is ``.esm`` or ``.esp`` (after trimming any ``.ghost``
-   *          extension), and that the ``TES4`` header can be parsed.
+   * @details The validity check is not exhaustive: it generally checks that the
+   *          file is a valid plugin file extension for the game and that its
+   *          header (if applicable) can be parsed.
    * @param  pluginPath
    *         The path to the file to check. Relative paths are resolved relative
    *         to the game's plugins directory, while absolute paths are used
@@ -107,10 +110,9 @@ public:
    *        the game's plugins directory, while absolute paths are used as
    *        given. Each plugin filename must be unique within the vector.
    * @param loadHeadersOnly
-   *        If true, only the plugins' ``TES4`` headers are loaded. If false,
-   *        all records in the plugins are parsed, apart from the main master
-   *        file if it has been identified by a previous call to
-   *        ``IdentifyMainMasterFile()``.
+   *        If true, only the plugins' headers are loaded. If false, all records
+   *        in the plugins are parsed, apart from the main master file if it has
+   *        been identified by a previous call to ``IdentifyMainMasterFile()``.
    */
   virtual void LoadPlugins(
       const std::vector<std::filesystem::path>& pluginPaths,
@@ -219,6 +221,9 @@ public:
 
   /**
    * @brief Set the game's load order.
+   * @details There is no way to persist the load order of inactive OpenMW
+   *          plugins, so setting an OpenMW load order will have no effect if
+   *          the relative order of active plugins is unchanged.
    * @param loadOrder
    *        A vector of plugin filenames sorted in the load order to set.
    */

include/loot/plugin_interface.h

@@ -44,7 +44,8 @@ public:
   /**
    * Get the plugin's filename.
    * @return The plugin filename. If the plugin was ghosted when it was loaded,
-   *         this filename will be without the .ghost suffix.
+   *         this filename will be without the .ghost suffix, unless the game is
+   *         OpenMW, in which case ghosted plugins are not supported.
    */
   virtual std::string GetName() const = 0;
 
@@ -88,8 +89,19 @@ public:
   virtual std::optional<uint32_t> GetCRC() const = 0;
 
   /**
-   * Check if the plugin's master flag is set.
-   * @return True if the master flag is set, false otherwise.
+   * Check if the plugin is a master plugin.
+   *
+   * What causes a plugin to be a master plugin varies by game, but is usually
+   * indicated by the plugin having its master flag set and/or by its file
+   * extension. However, OpenMW uses neither for determining plugins' load order
+   * so all OpenMW plugins are treated as non-masters.
+   *
+   * The term "master" is potentially confusing: a plugin A may not be a *master
+   * plugin*, but may still be a *master of* another plugin by being listed as
+   * such in that plugin's header record. Master plugins are sometimes referred
+   * to as *master files* or simply *masters*, while the other meaning is always
+   * referenced in relation to another plugin.
+   * @return True if the plugin is a master plugin, false otherwise.
    */
   virtual bool IsMaster() const = 0;