add method to locate additional config files

resources/resources.cpp

@@ -4,6 +4,10 @@
 #include <QLocale>
 #include <QTranslator>
 #include <QLibraryInfo>
+#include <QFile>
+#include <QDir>
+#include <QStringBuilder>
+#include <QSettings>
 #if defined(GUI_QTWIDGETS)
 # include <QApplication>
 # include <QIcon>
@@ -57,7 +61,7 @@ void loadQtTranslationFile()
     if(locale.language() != QLocale::English) {
         QTranslator *qtTranslator = new QTranslator;
         if(qtTranslator->load(QStringLiteral("qt_%1").arg(locale.name()),
-                          QLibraryInfo::location(QLibraryInfo::TranslationsPath))) {
+                              QLibraryInfo::location(QLibraryInfo::TranslationsPath))) {
             QCoreApplication::installTranslator(qtTranslator);
         } else if(qtTranslator->load(QStringLiteral("qt_%1").arg(locale.name()), QStringLiteral("../share/qt/translations"))) {
             // used in Windows
@@ -153,3 +157,53 @@ bool hasCoreApp()
 }
 
 }
+
+namespace ConfigFile {
+
+QString locateConfigFile(const QString &applicationName, const QString &fileName, const QSettings *settings)
+{
+    // check whether the file is in the current working directory
+    if(QFile::exists(fileName)) {
+        return fileName;
+    } else {
+        // check whether the file is in the settings directory used by QSettings
+        QString path;
+        if(settings) {
+            path = QFileInfo(settings->fileName()).absoluteDir().absoluteFilePath(fileName);
+            if(QFile::exists(path)) {
+                return path;
+            }
+        }
+        // check whether there is a user created version of the file under /etc/app/
+#if Q_OS_WIN32
+        // use relative paths on Windows
+        path = QStringLiteral("../etc/") % applicationName % QChar('/') % fileName;
+        if(QFile::exists(path)) {
+            return path;
+        } else {
+            // check whether there is the default version of the file under /usr/share/app/
+            path = QStringLiteral("../share/") % applicationName % QChar('/') % fileName;
+            if(QFile::exists(path)) {
+                return path;
+            } else {
+                return QString(); // file is not present
+            }
+        }
+#else
+        path = QStringLiteral("/etc/") % applicationName % QChar('/') % fileName;
+        if(QFile::exists(path)) {
+            return path;
+        } else {
+            // check whether there is the default version of the file under /usr/share/app/
+            path = QStringLiteral("/usr/share/") % applicationName % QChar('/') % fileName;
+            if(QFile::exists(path)) {
+                return path;
+            } else {
+                return QString(); // file is not present
+            }
+        }
+#endif
+    }
+}
+
+}

resources/resources.h

@@ -5,10 +5,9 @@
 
 #include <QtGlobal>
 
-QT_BEGIN_NAMESPACE
-class QString;
-class QStringList;
-QT_END_NAMESPACE
+QT_FORWARD_DECLARE_CLASS(QString)
+QT_FORWARD_DECLARE_CLASS(QStringList)
+QT_FORWARD_DECLARE_CLASS(QSettings)
 
 #define SET_QT_APPLICATION_INFO \
     QCoreApplication::setOrganizationName(QStringLiteral(APP_AUTHOR)); \
@@ -47,4 +46,10 @@ LIB_EXPORT bool hasCoreApp();
 
 }
 
+namespace ConfigFile {
+
+LIB_EXPORT QString locateConfigFile(const QString &applicationName, const QString &fileName, const QSettings *settings = nullptr);
+
+}
+
 #endif // RESOURCES_H