various: consolidated dir exists+mkpath into one function

app/common/filefunctions.cpp

@@ -150,27 +150,10 @@ void FileFunctions::CopyDirectory(const QString &source, const QString &dest, bo
   }
 }
 
-bool FileFunctions::DirectoryIsValid(const QString &dir, bool try_to_create)
+bool FileFunctions::DirectoryIsValid(const QDir &d, bool try_to_create_if_not_exists)
 {
-  // Empty string is invalid
-  if (dir.isEmpty()) {
-    return false;
-  }
-
-  QDir d(dir);
-
-  // If directory already exists, this is valid
-  if (d.exists()) {
-    return true;
-  }
-
-  // If we can create and creation is successful, this is valid
-  if (try_to_create && d.mkpath(".")) {
-    return true;
-  }
-
-  // Otherwise, invalid
-  return false;
+  // Return whether the directory exists, or whether it could be created if it doesn't
+  return d.exists() || d.mkpath(QStringLiteral("."));
 }
 
 QString FileFunctions::EnsureFilenameExtension(QString fn, const QString &extension)

app/common/filefunctions.h

@@ -21,6 +21,7 @@
 #ifndef FILEFUNCTIONS_H
 #define FILEFUNCTIONS_H
 
+#include <QDir>
 #include <QString>
 
 #include "common/define.h"
@@ -52,7 +53,7 @@ public:
 
   static void CopyDirectory(const QString& source, const QString& dest, bool overwrite = false);
 
-  static bool DirectoryIsValid(const QString& dir, bool try_to_create);
+  static bool DirectoryIsValid(const QDir& dir, bool try_to_create_if_not_exists = true);
 
   /**
    * @brief Ensures a given filename has a certain extension