Show notification count in tray icon.

src/trayicon.h

@@ -0,0 +1,67 @@
+#ifndef TRAYICON_H
+#define TRAYICON_H
+
+// Modified from mujx/nheko's TrayIcon.
+
+#include <QAction>
+#include <QIcon>
+#include <QIconEngine>
+#include <QPainter>
+#include <QRect>
+#include <QSystemTrayIcon>
+
+class MsgCountComposedIcon : public QIconEngine {
+ public:
+  MsgCountComposedIcon(const QString& filename);
+
+  virtual void paint(QPainter* p,
+                     const QRect& rect,
+                     QIcon::Mode mode,
+                     QIcon::State state);
+  virtual QIconEngine* clone() const;
+  virtual QList<QSize> availableSizes(QIcon::Mode mode,
+                                      QIcon::State state) const;
+  virtual QPixmap pixmap(const QSize& size,
+                         QIcon::Mode mode,
+                         QIcon::State state);
+
+  int msgCount = 0;
+
+ private:
+  const int BubbleDiameter = 14;
+
+  QIcon icon_;
+};
+
+class TrayIcon : public QSystemTrayIcon {
+  Q_OBJECT
+  Q_PROPERTY(QString iconSource READ iconSource WRITE setIconSource NOTIFY
+                 iconSourceChanged)
+  Q_PROPERTY(int notificationCount READ notificationCount WRITE
+                 setNotificationCount NOTIFY notificationCountChanged)
+ public:
+  TrayIcon(QObject* parent = nullptr);
+
+  QString iconSource() { return m_iconSource; }
+  void setIconSource(const QString& source);
+
+  int notificationCount() { return m_notificationCount; }
+  void setNotificationCount(int count);
+
+ signals:
+  void notificationCountChanged();
+  void iconSourceChanged();
+
+  void showWindow();
+
+ private:
+  QString m_iconSource;
+  int m_notificationCount = 0;
+
+  QAction* viewAction_;
+  QAction* quitAction_;
+
+  MsgCountComposedIcon* icon_;
+};
+
+#endif  // TRAYICON_H