Improve the 'jump to last read message' button

When loading a room, automatically load messages until the last read
message is loaded #35
Don't show the button if the message is not loaded

imports/NeoChat/Page/RoomPage.qml

@@ -329,7 +329,7 @@ Kirigami.ScrollablePage {
 
             id: goReadMarkerFab
 
-            visible: currentRoom && currentRoom.hasUnreadMessages || !messageListView.atYEnd
+            visible: currentRoom && currentRoom.hasUnreadMessages && currentRoom.readMarkerLoaded || !messageListView.atYEnd
             action: Kirigami.Action {
                 onTriggered: {
                     if (currentRoom && currentRoom.hasUnreadMessages) {

src/messageeventmodel.cpp

@@ -55,6 +55,19 @@ MessageEventModel::MessageEventModel(QObject *parent)
     qmlRegisterAnonymousType<FileTransferInfo>("org.kde.neochat", 1);
     qRegisterMetaType<FileTransferInfo>();
     qmlRegisterUncreatableType<EventStatus>("org.kde.neochat", 1, 0, "EventStatus", "EventStatus is not an creatable type");
+
+    QTimer::singleShot(0, this, [=]() {
+        m_currentRoom->getPreviousContent(50);
+        connect(this, &QAbstractListModel::rowsInserted, this, [=](){
+            if(m_currentRoom->readMarkerEventId().isEmpty()) {
+                return;
+            }
+            const auto it = m_currentRoom->findInTimeline(m_currentRoom->readMarkerEventId());
+            if (it == m_currentRoom->timelineEdge()) {
+                m_currentRoom->getPreviousContent(50);
+            }
+        });
+    });
 }
 
 MessageEventModel::~MessageEventModel()

src/neochatroom.cpp

@@ -56,6 +56,8 @@ NeoChatRoom::NeoChatRoom(Connection *connection, QString roomId, JoinState joinS
 
         NotificationsManager::instance().postNotification(id(), lastEvent->id(), displayName(), sender->displayname(this), eventToString(*lastEvent), avatar(128));
     });
+
+    connect(this, &Room::aboutToAddHistoricalMessages, this, &NeoChatRoom::readMarkerLoadedChanged);
 }
 
 void NeoChatRoom::uploadFile(const QUrl &url, const QString &body)
@@ -613,3 +615,9 @@ bool NeoChatRoom::canSendState(const QString &eventType) const
 
     return currentPl >= pl;
 }
+
+bool NeoChatRoom::readMarkerLoaded() const
+{
+    const auto it = findInTimeline(readMarkerEventId());
+    return it != timelineEdge();
+}

src/neochatroom.h

@@ -30,6 +30,7 @@ class NeoChatRoom : public Room
     Q_PROPERTY(bool hasFileUploading READ hasFileUploading WRITE setHasFileUploading NOTIFY hasFileUploadingChanged)
     Q_PROPERTY(int fileUploadingProgress READ fileUploadingProgress NOTIFY fileUploadingProgressChanged)
     Q_PROPERTY(QString avatarMediaId READ avatarMediaId NOTIFY avatarChanged STORED false)
+    Q_PROPERTY(bool readMarkerLoaded READ readMarkerLoaded NOTIFY readMarkerLoadedChanged)
 
 public:
     explicit NeoChatRoom(Connection *connection, QString roomId, JoinState joinState = {});
@@ -67,6 +68,8 @@ public:
         Q_EMIT fileUploadingProgressChanged();
     }
 
+    bool readMarkerLoaded() const;
+
     Q_INVOKABLE int savedTopVisibleIndex() const;
     Q_INVOKABLE int savedBottomVisibleIndex() const;
     Q_INVOKABLE void saveViewport(int topIndex, int bottomIndex);
@@ -108,6 +111,7 @@ Q_SIGNALS:
     void hasFileUploadingChanged();
     void fileUploadingProgressChanged();
     void backgroundChanged();
+    void readMarkerLoadedChanged();
 
 public Q_SLOTS:
     void uploadFile(const QUrl &url, const QString &body = "");