docs: add comments for functions that load history

src/widget/form/genericchatform.cpp

@@ -654,6 +654,11 @@ QDateTime GenericChatForm::getTime(const ChatLine::Ptr &chatLine) const
     return QDateTime();
 }
 
+/**
+ * @brief GenericChatForm::loadHistory load history
+ * @param time start date
+ * @param type indicates the direction of loading history
+ */
 void GenericChatForm::loadHistory(const QDateTime &time, const LoadHistoryDialog::LoadType type)
 {
     chatWidget->clear();
@@ -669,6 +674,10 @@ void GenericChatForm::loadHistory(const QDateTime &time, const LoadHistoryDialog
     }
 }
 
+/**
+ * @brief GenericChatForm::loadHistoryTo load history before to date "time" or before the first "messages" item
+ * @param time start date
+ */
 void GenericChatForm::loadHistoryTo(const QDateTime &time)
 {
     chatWidget->setScroll(false);
@@ -695,6 +704,11 @@ void GenericChatForm::loadHistoryTo(const QDateTime &time)
     }
 }
 
+/**
+ * @brief GenericChatForm::loadHistoryFrom load history starting from date "time" or from the last "messages" item
+ * @param time start date
+ * @return true if function loaded history else false
+ */
 bool GenericChatForm::loadHistoryFrom(const QDateTime &time)
 {
     chatWidget->setScroll(false);
@@ -707,11 +721,12 @@ 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) {
+    // The chatLog.getNextIdx() is usually 1 more than the idx on last "messages" item
+    // so if we have nothing to load, "add" is equal 1
+    if (add <= 1) {
         chatWidget->setScroll(true);
         return false;
     }
@@ -1157,11 +1172,17 @@ void GenericChatForm::goToCurrentDate()
     renderMessages(begin, end);
 }
 
+/**
+ * @brief GenericChatForm::loadHistoryLower load history after scrolling chatlog before first "messages" item
+ */
 void GenericChatForm::loadHistoryLower()
 {
     loadHistoryTo(QDateTime());
 }
 
+/**
+ * @brief GenericChatForm::loadHistoryUpper load history after scrolling chatlog after last "messages" item
+ */
 void GenericChatForm::loadHistoryUpper()
 {
     if (messages.empty()) {