QtUtils: Add UTF8CodePointCountValidator

Source/Core/DolphinQt/QtUtils/UTF8CodePointCountValidator.cpp

@@ -0,0 +1,20 @@
+// Copyright 2020 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include "DolphinQt/QtUtils/UTF8CodePointCountValidator.h"
+
+#include "Common/StringUtil.h"
+
+UTF8CodePointCountValidator::UTF8CodePointCountValidator(int max_count, QObject* parent)
+    : QValidator(parent), m_max_count(max_count)
+{
+}
+
+QValidator::State UTF8CodePointCountValidator::validate(QString& input, int& pos) const
+{
+  if (StringUTF8CodePointCount(input.toStdString()) > m_max_count)
+    return QValidator::Invalid;
+
+  return QValidator::Acceptable;
+}

Source/Core/DolphinQt/QtUtils/UTF8CodePointCountValidator.h

@@ -0,0 +1,19 @@
+// Copyright 2020 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <QString>
+#include <QValidator>
+
+class UTF8CodePointCountValidator : public QValidator
+{
+  Q_OBJECT
+public:
+  explicit UTF8CodePointCountValidator(int max_count, QObject* parent = nullptr);
+
+  QValidator::State validate(QString& input, int& pos) const override;
+
+  int m_max_count;
+};