feat: load messages from the database before date

src/chatlog/chatlog.cpp

@@ -677,7 +677,7 @@ void ChatLog::forceRelayout()
     startResizeWorker();
 }
 
-void ChatLog::checkVisibility()
+void ChatLog::checkVisibility(bool causedByScroll)
 {
     if (lines.empty())
         return;
@@ -717,12 +717,16 @@ void ChatLog::checkVisibility()
     if (!visibleLines.isEmpty()) {
         emit firstVisibleLineChanged(visibleLines.at(0));
     }
+
+    if (causedByScroll && lowerBound != lines.cend() && lowerBound->get()->row == 0) {
+        emit loadHistoryLower();
+    }
 }
 
 void ChatLog::scrollContentsBy(int dx, int dy)
 {
     QGraphicsView::scrollContentsBy(dx, dy);
-    checkVisibility();
+    checkVisibility(true);
 }
 
 void ChatLog::resizeEvent(QResizeEvent* ev)

src/chatlog/chatlog.h

@@ -72,6 +72,7 @@ signals:
     void selectionChanged();
     void workerTimeoutFinished();
     void firstVisibleLineChanged(const ChatLine::Ptr&);
+    void loadHistoryLower();
 
 public slots:
     void forceRelayout();
@@ -94,7 +95,7 @@ protected:
 
     void reposition(int start, int end, qreal deltaY);
     void updateSceneRect();
-    void checkVisibility();
+    void checkVisibility(bool causedByScroll = false);
     void scrollToBottom();
     void startResizeWorker();
 

src/widget/form/genericchatform.cpp

@@ -355,6 +355,7 @@ GenericChatForm::GenericChatForm(const Contact* contact, IChatLog& chatLog,
     connect(chatWidget, &ChatLog::customContextMenuRequested, this,
             &GenericChatForm::onChatContextMenuRequested);
     connect(chatWidget, &ChatLog::firstVisibleLineChanged, this, &GenericChatForm::updateShowDateInfo);
+    connect(chatWidget, &ChatLog::loadHistoryLower, this, &GenericChatForm::loadHistoryLower);
 
     connect(searchForm, &SearchForm::searchInBegin, this, &GenericChatForm::searchInBegin);
     connect(searchForm, &SearchForm::searchUp, this, &GenericChatForm::onSearchUp);
@@ -979,6 +980,19 @@ void GenericChatForm::renderMessages(ChatLogIdx begin, ChatLogIdx end,
     }
 }
 
+void GenericChatForm::loadHistoryLower()
+{
+    auto begin = messages.begin()->first;
+
+    if (begin.get() > 100) {
+        begin = ChatLogIdx(begin.get() - 100);
+    } else {
+        begin = ChatLogIdx(0);
+    }
+
+    renderMessages(begin, chatLog.getNextIdx());
+}
+
 void GenericChatForm::updateShowDateInfo(const ChatLine::Ptr& line)
 {
     const auto date = getTime(line);

src/widget/form/genericchatform.h

@@ -126,6 +126,8 @@ protected slots:
     void renderMessages(ChatLogIdx begin, ChatLogIdx end,
                         std::function<void(void)> onCompletion = std::function<void(void)>());
 
+    void loadHistoryLower();
+
 private:
     void retranslateUi();
     void addSystemDateMessage(const QDate& date);