Wrap json_load_file for UTF-8 support on Windows

Faceplates aren't loading if the RACK_USER_DIR has non-ASCII
characters in it. See:
https://community.vcvrack.com/t/rarebreeds-eugene-not-working/20266

Resolves issue #4.

src/OrbitsConfig.cpp

@@ -8,6 +8,19 @@ OrbitsConfig::OrbitsConfig(std::string path)
         m_path = path;
 }
 
+static json_t *orbits_json_load_file(const char *path, size_t flags, json_error_t *error)
+{
+        // json_load_file passes the input path to fopen, which doesn't support utf-8 paths
+        // on Windows. VCV Rack has worked around this by overriding fopen in common.hpp.
+        FILE* file = std::fopen(path, "rb");
+        json_t *json = json_loadf(file, flags, error);
+        if(file)
+        {
+                std::fclose(file);
+        }
+        return json;
+}
+
 float OrbitsConfig::rFindFloatAttribute(std::string &content, std::string attribute, size_t search)
 {
         search = content.rfind(attribute + "=", search);
@@ -33,7 +46,7 @@ std::string OrbitsConfig::getSvg(std::string component, int theme)
 {
         json_error_t error;
         std::string path = asset::plugin(pluginInstance, m_path);
-        json_t *root = json_load_file(path.c_str(), 0, &error);
+        json_t *root = orbits_json_load_file(path.c_str(), 0, &error);
         json_t *themes = json_object_get(root, "themes");
         json_t *entry = json_array_get(themes, theme);
         json_t *obj = json_object_get(entry, component.c_str());
@@ -86,7 +99,7 @@ std::string OrbitsConfig::getThemeName(int theme)
 {
         json_error_t error;
         std::string path = asset::plugin(pluginInstance, m_path);
-        json_t *root = json_load_file(path.c_str(), 0, &error);
+        json_t *root = orbits_json_load_file(path.c_str(), 0, &error);
         json_t *themes = json_object_get(root, "themes");
         json_t *entry = json_array_get(themes, theme);
         json_t *name = json_object_get(entry, "name");
@@ -106,7 +119,7 @@ int OrbitsConfig::getDefaultThemeId()
         int default_theme_id = 0;
         json_error_t error;
         std::string path = asset::plugin(pluginInstance, m_path);
-        json_t *root = json_load_file(path.c_str(), 0, &error);
+        json_t *root = orbits_json_load_file(path.c_str(), 0, &error);
         json_t *def = json_object_get(root, "default");
         const char *default_name = json_string_value(def);
         json_t *themes = json_object_get(root, "themes");
@@ -131,7 +144,7 @@ size_t OrbitsConfig::numThemes()
 {
         json_error_t error;
         std::string path = asset::plugin(pluginInstance, m_path);
-        json_t *root = json_load_file(path.c_str(), 0, &error);
+        json_t *root = orbits_json_load_file(path.c_str(), 0, &error);
         json_t *themes = json_object_get(root, "themes");
         size_t count = json_array_size(themes);
         json_decref(root);
@@ -142,7 +155,7 @@ std::array<uint8_t, 3> OrbitsConfig::getColour(std::string component, int theme)
 {
         json_error_t error;
         std::string path = asset::plugin(pluginInstance, m_path);
-        json_t *root = json_load_file(path.c_str(), 0, &error);
+        json_t *root = orbits_json_load_file(path.c_str(), 0, &error);
         json_t *themes = json_object_get(root, "themes");
         json_t *entry = json_array_get(themes, theme);
         json_t *obj = json_object_get(entry, component.c_str());