[Replay] Add a clickable replay history sidebar

Render the event index as a scrollable list of event boxes. Selecting an entry seeks the replay to that event and keeps the current event highlighted while playback advances.

cockatrice/src/interface/widgets/replay/replay_event_sidebar.h

@@ -0,0 +1,50 @@
+#ifndef COCKATRICE_REPLAY_EVENT_SIDEBAR_H
+#define COCKATRICE_REPLAY_EVENT_SIDEBAR_H
+
+#include <QList>
+#include <QWidget>
+#include <qtmetamacros.h>
+
+class GameReplay;
+class QLabel;
+class QListWidget;
+
+/**
+ * @brief A scrollable list of replay events that can be used to seek the replay.
+ *
+ * The sidebar copies the event data it needs at construction time. It does not keep a reference to the replay or to
+ * the replay manager.
+ */
+class ReplayEventSidebar : public QWidget
+{
+    Q_OBJECT
+
+public:
+    /**
+     * @param parent The parent widget
+     * @param replay The replay to build the event list from
+     * @param timeline Event index to time in milliseconds, as used by ReplayManager
+     */
+    ReplayEventSidebar(QWidget *parent, const GameReplay *replay, const QList<int> &timeline);
+
+public slots:
+    /**
+     * @brief Highlights the row of the event the game state has reached.
+     *
+     * @param eventIndex Index into the replay's event list, or -1 when nothing has been replayed yet
+     */
+    void setCurrentEvent(int eventIndex);
+
+signals:
+    void eventSelected(int eventIndex);
+
+private:
+    void setCurrentRow(int row);
+
+    QListWidget *eventList;
+    QLabel *emptyLabel;
+    QList<int> eventIndices; ///< Replay event index of each row, ascending
+    int currentRow = -1;
+};
+
+#endif // COCKATRICE_REPLAY_EVENT_SIDEBAR_H