Loading and End of Timeline Delegates

Add delegate for showing the user a loading indicator and for the beginning of the timeline.

BUG: 455045
BUG: 465285

src/models/timelinemodel.cpp

@@ -0,0 +1,95 @@
+// SPDX-FileCopyrightText: 2022 James Graham <james.h.graham@protonmail.com>
+// SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
+
+#include "timelinemodel.h"
+
+#include "delegatetype.h"
+
+TimelineModel::TimelineModel(QObject *parent)
+    : QConcatenateTablesProxyModel(parent)
+{
+    m_messageEventModel = new MessageEventModel(this);
+    addSourceModel(m_messageEventModel);
+    m_timelineEndModel = new TimelineEndModel(this);
+    addSourceModel(m_timelineEndModel);
+}
+
+NeoChatRoom *TimelineModel::room() const
+{
+    return m_messageEventModel->room();
+}
+
+void TimelineModel::setRoom(NeoChatRoom *room)
+{
+    // Both models do their own null checking so just pass along.
+    m_messageEventModel->setRoom(room);
+    m_timelineEndModel->setRoom(room);
+}
+
+MessageEventModel *TimelineModel::messageEventModel() const
+{
+    return m_messageEventModel;
+}
+
+QHash<int, QByteArray> TimelineModel::roleNames() const
+{
+    return m_messageEventModel->roleNames();
+}
+
+TimelineEndModel::TimelineEndModel(QObject *parent)
+    : QAbstractListModel(parent)
+{
+}
+
+void TimelineEndModel::setRoom(NeoChatRoom *room)
+{
+    if (room == m_room) {
+        return;
+    }
+
+    beginResetModel();
+
+    if (m_room != nullptr) {
+        m_room->disconnect(this);
+    }
+
+    m_room = room;
+
+    if (m_room != nullptr) {
+        connect(m_room, &Quotient::Room::eventsHistoryJobChanged, this, [this]() {
+            if (m_room->allHistoryLoaded()) {
+                // HACK: We have to do it this way because DelegateChooser doesn't update dynamically.
+                beginRemoveRows({}, 0, 0);
+                endRemoveRows();
+                beginInsertRows({}, 0, 0);
+                endInsertRows();
+            }
+        });
+    }
+
+    endResetModel();
+}
+
+QVariant TimelineEndModel::data(const QModelIndex &idx, int role) const
+{
+    Q_UNUSED(idx)
+    if (m_room == nullptr) {
+        return {};
+    }
+
+    if (role == DelegateTypeRole) {
+        return m_room->allHistoryLoaded() ? DelegateType::TimelineEnd : DelegateType::Loading;
+    }
+    return {};
+}
+
+int TimelineEndModel::rowCount(const QModelIndex &parent) const
+{
+    Q_UNUSED(parent)
+    return 1;
+}
+
+QHash<int, QByteArray> TimelineEndModel::roleNames() const
+{
+    return {{DelegateTypeRole, "delegateType"}};
+}