revert(chatlog): "scroll bar stuck to bottom (fix #5755)"

This reverts commit 38df897e02.

src/widget/form/genericchatform.cpp

@@ -726,7 +726,7 @@ void GenericChatForm::loadHistoryTo(const QDateTime &time)
     }
 }
 
-bool GenericChatForm::loadHistoryFrom(const QDateTime &time)
+void GenericChatForm::loadHistoryFrom(const QDateTime &time)
 {
     chatWidget->setScroll(false);
     auto begin = chatLog.getFirstIdx();
@@ -738,20 +738,10 @@ bool GenericChatForm::loadHistoryFrom(const QDateTime &time)
 
     int add = DEF_NUM_MSG_TO_LOAD;
     if (begin.get() + DEF_NUM_MSG_TO_LOAD > chatLog.getNextIdx().get()) {
-        auto t = chatLog.getNextIdx();
         add = chatLog.getNextIdx().get() - begin.get();
     }
-
-    if (add  <= 1) {
-        chatWidget->setScroll(true);
-        return false;
-    }
-
     auto end = ChatLogIdx(begin.get() + add);
-
     renderMessages(begin, end);
-
-    return true;
 }
 
 void GenericChatForm::removeFirstsMessages(const int num)
@@ -1219,9 +1209,8 @@ void GenericChatForm::loadHistoryUpper()
     }
 
     auto msg = messages.crbegin()->second;
-    if (loadHistoryFrom(QDateTime())) {
-        chatWidget->scrollToLine(msg);
-    }
+    loadHistoryFrom(QDateTime());
+    chatWidget->scrollToLine(msg);
 }
 
 void GenericChatForm::updateShowDateInfo(const ChatLine::Ptr& prevLine, const ChatLine::Ptr& topLine)

src/widget/form/genericchatform.h

@@ -130,7 +130,7 @@ private:
     QDateTime getTime(const ChatLine::Ptr& chatLine) const;
     void loadHistory(const QDateTime& time, const LoadHistoryDialog::LoadType type);
     void loadHistoryTo(const QDateTime& time);
-    bool loadHistoryFrom(const QDateTime& time);
+    void loadHistoryFrom(const QDateTime& time);
     void removeFirstsMessages(const int num);
     void removeLastsMessages(const int num);