行情区图表：成交量、十字线 OHLCV、可视高低点、日线满 500 根

Co-authored-by: Cursor <cursoragent@cursor.com>

hub_ohlcv_lib.py

@@ -40,6 +40,7 @@ def last_closed_bar_open_ms(timeframe: str, now_ms: int | None = None) -> int:
 
 
 def window_start_ms(timeframe: str, need: int, retention_days: int, now_ms: int | None = None) -> int:
+    """本地库清理/读库窗口：不超过 retention_days。"""
     now = int(now_ms if now_ms is not None else time.time() * 1000)
     period = TIMEFRAME_MS[normalize_chart_timeframe(timeframe)]
     retention_cutoff = now - max(1, int(retention_days)) * 86400000
@@ -47,6 +48,13 @@ def window_start_ms(timeframe: str, need: int, retention_days: int, now_ms: int
     return max(retention_cutoff, want)
 
 
+def chart_fetch_start_ms(timeframe: str, need: int, now_ms: int | None = None) -> int:
+    """行情展示拉取起点：按 need 根回看（日线 500 / 日内 1000），不受 DB 保留天数限制。"""
+    now = int(now_ms if now_ms is not None else time.time() * 1000)
+    period = TIMEFRAME_MS[normalize_chart_timeframe(timeframe)]
+    return max(0, now - max(1, int(need)) * period)
+
+
 def price_tick_from_market(exchange, exchange_symbol: str) -> Optional[float]:
     try:
         markets = getattr(exchange, "markets", None) or {}