gh-124927: Fix conversion issue between coordinates and position in REPL

Author: ImFeH2

Lib/_pyrepl/reader.py

@@ -576,11 +576,10 @@ def setpos_from_xy(self, x: int, y: int) -> None:
         j = 0
         cur_x = self.screeninfo[i][0]
         while cur_x < x:
-            if self.screeninfo[i][1][j] == 0:
-                continue
-            cur_x += self.screeninfo[i][1][j]
+            if self.screeninfo[i][1][j] != 0:
+                pos += 1
+            cur_x += 1
             j += 1
-            pos += 1
 
         self.pos = pos
 
@@ -607,7 +606,17 @@ def pos2xy(self) -> tuple[int, int]:
             else:
                 pos -= l + 1  # +1 cause newline is in buffer
             y += 1
-        return p + sum(l2[:pos]), y
+
+        x = p
+        i = 0
+        cnt = 0
+        while cnt < pos:
+            if l2[i]:
+                cnt += 1
+            x += 1
+            i += 1
+
+        return x, y
 
     def insert(self, text: str | list[str]) -> None:
         """Insert 'text' at the insertion point."""

Lib/test/test_pyrepl/test_reader.py

@@ -312,3 +312,23 @@ def test_key_press_on_tab_press_once(self):
         reader, _ = handle_all_events(events, prepare_reader=completing_reader)
 
         self.assert_screen_equals(reader, f"{code}a")
+
+    def test_setpos_from_xy_for_non_printing_char(self):
+        code = "# non \u200c printing character"
+        events = code_to_events(code)
+
+        reader, _ = handle_all_events(events)
+        reader.setpos_from_xy(8, 0)
+
+        self.assertEqual(reader.pos, 6)
+
+    def test_pos2xy_for_non_printing_char(self):
+        code = "# non\u200cprinting character"
+        events = code_to_events(code)
+
+        reader, _ = handle_all_events(events)
+        reader.pos = 6
+        x, y = reader.pos2xy()
+
+        self.assertEqual(x, 11)
+        self.assertEqual(y, 0)