Add new global shortcut system backend for X11 and Windows

- Remove qxt
- Also create an option for enabled/disabling shortcuts through X11.

src/globalshortcuts/globalshortcut.h

@@ -0,0 +1,80 @@
+/*
+ * Strawberry Music Player
+ * Copyright 2018, Jonas Kvinge <jonas@jkvinge.net>
+ *
+ * Strawberry is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Strawberry is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Strawberry.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef GLOBALSHORTCUT_H
+#define GLOBALSHORTCUT_H
+
+#include "config.h"
+
+#include <stdbool.h>
+
+#include <QtGlobal>
+#include <QObject>
+#include <QAbstractNativeEventFilter>
+#include <QKeySequence>
+#include <QPair>
+#include <QVector>
+#include <QHash>
+#include <QByteArray>
+
+class GlobalShortcutBackend;
+
+class GlobalShortcut : public QObject, QAbstractNativeEventFilter {
+  Q_OBJECT
+
+ public:
+  explicit GlobalShortcut(QObject *parent = nullptr);
+  explicit GlobalShortcut(QKeySequence shortcut, GlobalShortcutBackend *backend, QObject *parent = nullptr);
+  ~GlobalShortcut();
+
+  GlobalShortcutBackend *backend() const { return backend_; }
+  QKeySequence shortcut() const { return shortcut_; }
+
+  bool setShortcut(const QKeySequence &shortcut);
+  bool unsetShortcut();
+
+ signals:
+  void activated();
+
+ private:
+
+  void activateShortcut(quint32 native_key, quint32 native_mods);
+
+  quint32 nativeModifiers(Qt::KeyboardModifiers qt_mods);
+  quint32 nativeKeycode(Qt::Key qt_keycode);
+
+  bool registerShortcut(quint32 native_key, quint32 native_mods);
+  bool unregisterShortcut(quint32 native_key, quint32 native_mods);
+
+  bool nativeEventFilter(const QByteArray &eventtype, void *message, long *result);
+
+  static GlobalShortcut *initialized_;
+  static QHash<QPair<quint32, quint32>, GlobalShortcut*> internal_shortcuts_;
+  static const QVector<quint32> mask_modifiers_;
+
+  GlobalShortcutBackend *backend_;
+  QKeySequence shortcut_;
+  Qt::Key qt_key_;
+  Qt::KeyboardModifiers qt_mods_;
+  quint32 native_key_;
+  quint32 native_mods_;
+
+};
+
+#endif  // GLOBALSHORTCUT_H