add follow tail feature

src/ui/ScaledScrollBar.py

@@ -18,6 +18,9 @@ class ScaledScrollBar(QScrollBar):
         code involved. We work around this by converting the python int 
         into a string."""
 
+    scrolled_to_end = Signal(bool)
+    """Signal emitted when the scroll bar value is set."""
+
     def __init__(self):
         super(ScaledScrollBar, self).__init__()
         self.real_maximum = self.maximum()
@@ -46,6 +49,7 @@ class ScaledScrollBar(QScrollBar):
             super().setMaximum(maximum)
 
     def _valueChanged(self, value: int):
+        self.scrolled_to_end.emit(value == self.maximum() and value > 0)
         if self.is_huge:
             real_value = (value / self.maximum()) * self.real_maximum
             # print("scaled value changed: %d -> %d (%f)" % (value, real_value, value / self.maximum()))