add 'system.max-bg-asset-loaders' setting

src/assets/AssetsLoader.cpp

@@ -371,12 +371,13 @@ public:
     }
 };
 
-std::shared_ptr<Task> AssetsLoader::startTask(runnable onDone) {
+std::shared_ptr<Task> AssetsLoader::startTask(runnable onDone, int maxWorkers) {
     auto pool =
         std::make_shared<util::ThreadPool<aloader_entry, assetload::postfunc>>(
             "assets-loader-pool",
             [=]() { return std::make_shared<LoaderWorker>(this); },
-            [this](const assetload::postfunc& func) { func(&assets); }
+            [this](const assetload::postfunc& func) { func(&assets); },
+            maxWorkers
         );
     pool->setOnComplete(std::move(onDone));
     pool->setJobsSource([this]() -> std::optional<aloader_entry> {

src/assets/AssetsLoader.hpp

@@ -113,7 +113,7 @@ public:
     /// @throws assetload::error
     void loadNext();
 
-    std::shared_ptr<Task> startTask(runnable onDone);
+    std::shared_ptr<Task> startTask(runnable onDone, int maxWorkers);
 
     const ResPaths& getPaths() const;
     aloader_func getLoader(AssetType tag);

src/engine/AssetsManagement.cpp

@@ -12,7 +12,9 @@
 
 static debug::Logger logger("assets-management");
 
-AssetsManagement::AssetsManagement(Engine& engine) : engine(engine) {}
+AssetsManagement::AssetsManagement(Engine& engine)
+    : engine(engine), settings(engine.getSettings()) {
+}
 
 AssetsManagement::~AssetsManagement() {
     finishBackgroundLoader();
@@ -36,7 +38,9 @@ AssetsLoader& AssetsManagement::acquireBackgroundLoader() {
     backgroundLoader = std::make_unique<AssetsLoader>(
         engine, *assets, engine.getResPaths()
     );
-    backgroundLoaderTask = backgroundLoader->startTask(nullptr);
+    backgroundLoaderTask = backgroundLoader->startTask(
+        nullptr, settings.system.maxBgAssetLoaders.get()
+    );
     return *backgroundLoader;
 }
 
@@ -56,7 +60,9 @@ void AssetsManagement::loadAssets(Content* content) {
     // todo: before setting to true, check if GLSLExtension thread safe 
     bool threading = false; // look at three upper lines
     if (threading) {
-        auto task = loader.startTask([=](){});
+        auto task = loader.startTask(
+            [=]() {}, 0
+        );
         task->waitForEnd();
     } else {
         while (loader.hasNext()) {

src/engine/AssetsManagement.hpp

@@ -8,6 +8,7 @@ class AssetsLoader;
 class Engine;
 class Content;
 class Task;
+struct EngineSettings;
 
 class AssetsManagement final {
 public:
@@ -25,6 +26,7 @@ private:
     void finishBackgroundLoader();
 
     Engine& engine;
+    const EngineSettings& settings;
     std::unique_ptr<Assets> assets;
     std::unique_ptr<AssetsLoader> backgroundLoader;
     std::shared_ptr<Task> backgroundLoaderTask;

src/io/settings_io.cpp

@@ -94,6 +94,9 @@ SettingsHandler::SettingsHandler(EngineSettings& settings) {
     builder.add("do-write-lights", &settings.debug.doWriteLights);
     builder.add("do-trace-shaders", &settings.debug.doTraceShaders);
     builder.add("enable-experimental", &settings.debug.enableExperimental);
+
+    builder.addSection("system");
+    builder.add("max-bg-asset-loaders", &settings.system.maxBgAssetLoaders);
 }
 
 dv::value SettingsHandler::getValue(const std::string& name) const {

src/logic/scripting/lua/libs/libpack.cpp

@@ -90,7 +90,7 @@ static int l_pack_get_info(
         auto& assetsLoader = engine->acquireBackgroundLoader();
         std::string icon = pack.id + ".icon";
         if (!AssetsLoader::loadExternalTexture(
-                assetsLoader, icon, {pack.folder / "icon"}
+                assetsLoader, icon, {pack.folder / "icon.png"}
             )) {
             icon = "gui/no_icon";
         }

src/logic/scripting/lua/libs/libworld.cpp

@@ -60,8 +60,8 @@ static int l_get_list(lua::State* L) {
         if (!engine->isHeadless() && !AssetsLoader::loadExternalTexture(
                 engine->acquireBackgroundLoader(),
                 icon,
-                {worlds[i] / "icon",
+                {worlds[i] / "icon.png",
-                 worlds[i] / "preview"}
+                 worlds[i] / "preview.png"}
             )) {
             icon = "gui/no_world_icon";
         }

src/settings.hpp

@@ -115,6 +115,10 @@ struct UiSettings {
 struct NetworkSettings {
 };
 
+struct SystemSettings {
+    IntegerSetting maxBgAssetLoaders {3, -4, 16};
+};
+
 struct EngineSettings {
     AudioSettings audio;
     DisplaySettings display;
@@ -125,4 +129,5 @@ struct EngineSettings {
     UiSettings ui;
     NetworkSettings network;
     PathfindingSettings pathfinding;
+    SystemSettings system;
 };