src/ui/bigtext/bigtext.py

@@ -131,7 +131,7 @@ class BigText(QWidget):
 # noinspection PyArgumentList,PyTypeChecker
 class InnerBigText(QWidget):
     _byte_offset = 0
-    _left_offset = 0
+    _left_offset = 0  # number of characters the horizontal scrollbar was moved to the right
     scroll_lines = 0
     longest_line = 0
 
@@ -504,12 +504,17 @@ class InnerBigText(QWidget):
         y_line_offset = self.char_height
         for line in self.lines:
             text = line.line_prepared_for_display()
-            painter.drawText(left_offset, y_line_offset, text)
+            leftmost_visible_char_index = line.column_to_char(self._left_offset - 1)
+            rightmost_visible_char_index = line.column_to_char(self._left_offset + math.ceil(self.columns_shown()))
+            text = text[
+                   leftmost_visible_char_index:rightmost_visible_char_index]  # reduce string to the visible section before drawing
+            painter.drawText(0, y_line_offset, text)
+            # painter.drawText(left_offset, y_line_offset, text)
             y_line_offset = y_line_offset + self.char_height
 
         painter.end()
         end_ns = time.process_time_ns()
-        #print(f"paint took {(end_ns - start_ns) / 1000000.0}")
+        print(f"paint took {(end_ns - start_ns) / 1000000.0}")
 
     def draw_highlights(self, highlights: [HighlightedRange], painter: QPainter, y_line_offset: int):