Refactor: split ScanScreen window-capture into 3 private methods

client/ScreenSpy.h

@@ -266,6 +266,14 @@ public:
         m_hDeskTopDC = GetDC(NULL);
         m_data.Create(m_hDeskTopDC, m_iScreenX, m_iScreenY, m_ulFullWidth, m_ulFullHeight);
     }
+
+private:
+    // 前景跟踪：切换或尺寸变化时更新 m_hTargetWnd，返回 false 表示本帧冻结
+    bool UpdateDynamicForeground();
+    // 防抖 + 重建检测：更新 m_iScreenX/Y，返回 false 表示本帧冻结
+    bool CheckWindowResize();
+    // 执行实际像素拷贝（BitBlt 或 PrintWindow）
+    void CaptureWindowContent(HDC hdcDest, HDC hdcSour, ULONG ulWidth, ULONG ulHeight);
 };
 
 #endif // !defined(AFX_SCREENSPY_H__5F74528D_9ABD_404E_84D2_06C96A0615F4__INCLUDED_)