nwge-docs

Engine Initialization

Nwge is initialized in 3 distinct stages:

1. Pre-initialization
2. The main function
3. Initialization

Pre-initialization

The first stage is pre-initialization, which takes place as soon as your app starts, but before your main is called. This is achieved by the <nwge/main.hpp> header, which provides its own main function and silently renames your main function to nwgeAppMain. This main function provided by nwge simply calls the nwge::launch function with a pointer to your main function. Pre-initialization is performed in nwge::launch. In case pre-initialization fails, your main is never called. That way, you can assume most of nwge’s systems are already initialized and ready to go by the time execution reaches your main function.

Pre-initialization consists of the following:

1. Register signal handlers
2. Pre-initialize console (set up internal pointer tables)
3. Calculate engine paths
4. Initialize SDL (and set up internal system cursor pointer table)
5. Initialize renderer (with invisible window)
6. Initialize engine GUIs
7. Post-initialize console (print help message)

Note that at this point, we don’t know the app name yet. This means we cannot load a user configuration file for the app, so a path is not calculated for it.

If all of the above steps complete successfully, execution is then handed off to your main function.

The main function

You likely have a simple, bare bones main that looks something like this:

s32 main([[maybe_unused]] s32 argc, [[maybe_unused]] CStr *argv) {
  nwge::startPtr(createState(), {
    .appName = "My Nwge App",
  });
  return 0;
}

Such a main function simply passes execution back to nwge without doing anything extra. Having such a main function is useful, however, if you wish to parse command-line arguments (using libnwge_cli, for example) before starting your app. This also means you can early out in case something goes wrong during that process.

Initialization

The rest of the initialization is performed from your call to startPtr (start is just a wrapper over startPtr). This is where initialization that needs the developer configuration is performed.

Pre-initialization consists of the following:

1. Initialize configuration manager
2. Update previously calculated paths (e.g. config path as now we have app name for it)
3. Load user configuration
4. Renderer post-initialization tasks (e.g. make the window visible)
5. Preload state
6. Enter main engine loop

At this point nwge retakes execution and finishes everything that wasn’t fully initialized. For example, the user’s app config is loaded here, since we didn’t know the app name before (the config file is named after the app). We also re-initialize any Store paths.

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