Add a new function to get current locale (#1405)

Author: kingysu

src/lib/fcitx/instance.cpp

@@ -185,22 +185,13 @@ void InstanceArgument::printUsage() const {
 
 InstancePrivate::InstancePrivate(Instance *q) : QPtrHolder<Instance>(q) {
 #ifdef ENABLE_KEYBOARD
-    auto locale = getEnvironment("LC_ALL");
-    if (!locale) {
-        locale = getEnvironment("LC_CTYPE");
-    }
-    if (!locale) {
-        locale = getEnvironment("LANG");
-    }
-    if (!locale) {
-        locale = "C";
-    }
-    assert(locale.has_value());
+    const auto &locale = getCurrentLocale();
+    assert(!locale.empty());
     xkbContext_.reset(xkb_context_new(XKB_CONTEXT_NO_FLAGS));
     if (xkbContext_) {
         xkb_context_set_log_level(xkbContext_.get(), XKB_LOG_LEVEL_CRITICAL);
         xkbComposeTable_.reset(xkb_compose_table_new_from_locale(
-            xkbContext_.get(), locale->data(), XKB_COMPOSE_COMPILE_NO_FLAGS));
+            xkbContext_.get(), locale.data(), XKB_COMPOSE_COMPILE_NO_FLAGS));
         if (!xkbComposeTable_) {
             FCITX_INFO()
                 << "Trying to fallback to compose table for en_US.UTF-8";

src/lib/fcitx/misc_p.h

@@ -227,14 +227,24 @@ static inline bool hasTwoKeyboardInCurrentGroup(Instance *instance) {
     return false;
 }
 
-static inline std::string getCurrentLanguage() {
-    for (const char *vars : {"LC_ALL", "LC_MESSAGES", "LANG"}) {
-        auto lang = getEnvironment(vars);
+static inline std::string
+getEnvVariableValue(const std::vector<std::string> &variableList,
+                    const char *defaultValue) {
+    for (const auto &vars : variableList) {
+        auto lang = getEnvironment(vars.c_str());
         if (lang && !lang->empty()) {
             return std::move(*lang);
         }
     }
-    return "";
+    return defaultValue;
+}
+
+static inline std::string getCurrentLanguage() {
+    return getEnvVariableValue({"LC_ALL", "LC_MESSAGES", "LANG"}, "");
+}
+
+static inline std::string getCurrentLocale() {
+    return getEnvVariableValue({"LC_ALL", "LC_CTYPE", "LANG"}, "C");
 }
 
 static inline std::string stripLanguage(const std::string &lc) {