0. Memory leak: under not WARP-Adapter, memory leak detected by ID3D11Debug at end of program
  [2015/09/07] bug for microsoft, microsoft fixed it

1. Memory leak in Accessible under Windows 7.
  ref: https://social.msdn.microsoft.com/Forums/windowsdesktop/en-US/4986251c-3aea-4c4b-b8ea-dc77e3566a65/releasing-irawelementprovidersimple-implementations?forum=windowsaccessibilityandautomation

2. Memory leak on OutOfMemory
  well, well...

3. WinA : WM_MOUSELEAVE, WinB: WM_MOUSEMOVE message sequential maybe* orderless. make UIViewport's Event_MouseEnter/Event_MouseLeave orderless
  you should handle both situations.
  * : if mouse move fast as you can(just 1 frame), you will get WM_MOUSEMOVE(B) at first, then WM_MOUSELEAVE(A)

4.