Unify translation files loading action

Since it is possible alternative WebUI could be coded in languages other than English,
WebUI must be able to load user-provided webui_en.qm.
At least one translated string must exist in order to generate an usable .qm file.

src/webui/webapplication.cpp

@@ -199,10 +199,6 @@ void WebApplication::translateDocument(QString &data)
 {
     const QRegularExpression regex("QBT_TR\\((([^\\)]|\\)(?!QBT_TR))+)\\)QBT_TR\\[CONTEXT=([a-zA-Z_][a-zA-Z0-9_]*)\\]");
 
-    const bool isTranslationNeeded = !m_currentLocale.startsWith("en")
-            || m_currentLocale.startsWith("en_AU") || m_currentLocale.startsWith("en_GB")
-            || !m_translator.isEmpty();
-
     int i = 0;
     bool found = true;
     while (i < data.size() && found) {
@@ -212,12 +208,12 @@ void WebApplication::translateDocument(QString &data)
             const QString sourceText = regexMatch.captured(1);
             const QString context = regexMatch.captured(3);
 
-            QString translation = sourceText;
-            if (isTranslationNeeded) {
-                const QString loadedText = m_translator.translate(context.toUtf8().constData(), sourceText.toUtf8().constData(), nullptr, 1);
-                if (!loadedText.isEmpty())
-                    translation = loadedText;
-            }
+            const QString loadedText = m_translationFileLoaded
+                ? m_translator.translate(context.toUtf8().constData(), sourceText.toUtf8().constData())
+                : QString();
+            // `loadedText` is empty when translation is not provided
+            // it should fallback to `sourceText`
+            QString translation = loadedText.isEmpty() ? sourceText : loadedText;
 
             // Use HTML code for quotes to prevent issues with JS
             translation.replace('\'', "&#39;");
@@ -436,13 +432,14 @@ void WebApplication::configure()
     if (m_currentLocale != newLocale) {
         m_currentLocale = newLocale;
         m_translatedFiles.clear();
-        if (m_translator.load(m_rootFolder + QLatin1String("/translations/webui_") + m_currentLocale)) {
-            LogMsg(tr("Web UI translation for selected locale (%1) is successfully loaded.")
-                   .arg(m_currentLocale));
+
+        m_translationFileLoaded = m_translator.load(m_rootFolder + QLatin1String("/translations/webui_") + newLocale);
+        if (m_translationFileLoaded) {
+            LogMsg(tr("Web UI translation for selected locale (%1) has been successfully loaded.")
+                   .arg(newLocale));
         }
         else {
-            LogMsg(tr("Couldn't load Web UI translation for selected locale (%1). Falling back to default (en).")
-                   .arg(m_currentLocale), Log::WARNING);
+            LogMsg(tr("Couldn't load Web UI translation for selected locale (%1).").arg(newLocale), Log::WARNING);
         }
     }
 

src/webui/webapplication.h

@@ -146,6 +146,7 @@ private:
     QMap<QString, TranslatedFile> m_translatedFiles;
     QString m_currentLocale;
     QTranslator m_translator;
+    bool m_translationFileLoaded = false;
 
     bool m_isLocalAuthEnabled;
     bool m_isAuthSubnetWhitelistEnabled;

src/webui/www/translations/webui_en.ts

@@ -5,7 +5,7 @@
     <name>AboutDlg</name>
     <message>
         <source>About</source>
-        <translation type="unfinished" />
+        <translation>About</translation>
     </message>
 </context>
 <context>