chatgui: add scroll-to-bottom floating button, incremental message refresh via getMessagesSince

tools/chatgui/src/chatview.h

@@ -3,6 +3,7 @@
 #include <QListView>
 #include <QPersistentModelIndex>
 #include <QPoint>
+#include <QPushButton>
 
 struct ChatTextSelection {
     QPersistentModelIndex index;
@@ -43,6 +44,7 @@ protected:
 
 private:
     void copySelection();
+    void updateScrollDownBtn();
 
     QPixmap m_background;
     QPersistentModelIndex m_selStart;
@@ -52,4 +54,5 @@ private:
     QPersistentModelIndex m_pressIndex;
     QPoint m_pressPos;
     bool m_selecting = false;
+    QPushButton *m_scrollDownBtn = nullptr;
 };