diff --git a/bigtext.py b/bigtext.py
index 78d2940..2d66164 100644
--- a/bigtext.py
+++ b/bigtext.py
@@ -117,6 +117,11 @@ class InnerBigText(QWidget):
             self.selection_highlight.set_end_byte(current_byte)
             self.update()
             # print("-> %s,%s" %(self._selection_start_byte, self._selection_end_byte))
+        line_number = self.y_pos_to_line(e.pos().y())
+        if line_number == 0:
+            self.scroll_by_lines(-1)
+        if line_number+1 >= int(self.lines_shown()):
+            self.scroll_by_lines(1)
 
     def h_scroll_event(self, left_offset: int):
         self._left_offset = left_offset
@@ -135,8 +140,11 @@ class InnerBigText(QWidget):
             maximum = max(0, length - width_in_chars+1)
             self.parent.h_scroll_bar.setMaximum(maximum)
 
+    def y_pos_to_line(self, y: int):
+        return int(y / self.char_height)
+
     def to_byte_offset(self, e: QMouseEvent) -> int:
-        line_number = int(e.pos().y() / self.char_height)
+        line_number = self.y_pos_to_line(e.pos().y())
 
         if line_number < len(self.lines):
             line = self.lines[line_number]