fix column_to_char for tabs

src/ui/bigtext/line.py

@@ -77,8 +77,12 @@ class Line:
         return result
 
     def column_to_char(self, column_in_line: int) -> int:
+        while not column_in_line in self._column_to_char_cache and column_in_line > 0:
+            column_in_line = column_in_line - 1
+
         if column_in_line in self._column_to_char_cache:
             return self._column_to_char_cache[column_in_line]
+
         return 0
 
     def char_to_column(self, char_in_line: int) -> int:

src/ui/bigtext/testline.py

@@ -11,7 +11,11 @@ from line import Line
 class MyTestCase(unittest.TestCase):
     def test_column_to_char(self):
         byte_offset = 123
-        text = "\tabc\td\tef\tg"  # will be rendered as: ....abc.d...ef..g  where . represents a whitespace column
+        # will be rendered as:
+        # ....abc.d...ef..g  where . represents a whitespace column
+        # 00001234566678991  character index
+        # 01234567890123456  colum index
+        text = "\tabc\td\tef\tg"
         line = Line(byte_offset=byte_offset, byte_end=byte_offset + len(text.encode("utf8")), line=text)
 
         self.assertEqual(0, line.column_to_char(0))  # the tab
@@ -99,8 +103,8 @@ class MyTestCase(unittest.TestCase):
         print(text)
         line = Line(byte_offset=byte_offset, byte_end=byte_offset + len(text.encode("utf8")), line=text)
         self.assertEqual(0, line.byte_index_to_char_index(0))  # x
-        self.assertEqual(0, line.byte_index_to_char_index(1))  # first byte of diacritical mark belonging to x
-        self.assertEqual(0, line.byte_index_to_char_index(2))  # second byte of diacritical mark belonging to x
+        self.assertEqual(1, line.byte_index_to_char_index(1))  # first byte of diacritical mark belonging to x
+        self.assertEqual(1, line.byte_index_to_char_index(2))  # second byte of diacritical mark belonging to x
 
     def test_diacritical_marks(self):
         text = "̈ẍỏôŏ̮👍🏿"