Fix: 补回 _on_point_changed 方法

main.py

@@ -590,6 +590,23 @@ class MainWindow(QMainWindow):
         self.lbl_hint.setStyleSheet("color: #888; font-size: 11px;")
         self._update_display()
 
+    # ══════════════ 选点回调 ═════════════════════════════
+
+    def _on_point_changed(self, mode: str, pt: tuple) -> None:
+        x, y = int(round(pt[0])), int(round(pt[1]))
+        if mode == "o":
+            self.lbl_o.setText(f"({x}, {y})")
+            self.lbl_hint.setText("点击画面选 M")
+        elif mode == "m":
+            self.lbl_m.setText(f"({x}, {y})")
+            if not self._measuring:
+                self.lbl_hint.setText("点击画面选 M2，或点「开始测量」")
+        elif mode == "m2":
+            self.lbl_m2.setText(f"({x}, {y})")
+            self._update_display()
+            if self._measuring:
+                self._record_and_advance()
+
     # ══════════════ 方向矫正 ═════════════════════════════
 
     def _on_flip_toggled(self, checked: bool) -> None: