Multiple OnParentNotify message sent to ActiveX control on mouse operation

By design Issue #1016513


Oct 30, 2014
This issue is public.
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Steps to reproduce


Repro Steps:

Download sample from:

Issue occurs only in Win 8.1 IE11 machine

  1. Register (regsvr32) BullsEyeCtl.dll
  2. Build the solution ATLCont6.sln in 32 bit and register the ATLCont6.dll from Debug folder.
  3. Launch the file contain.htm in Internet Explorer which loads ATL Container control ATLCont6 and this container hosts the Bulls Eye control.
  4. Debug in Visual Studio by attaching the IE tab process which has contain.htm loaded.
  5. Put a breakpoint in the below function in contain.htm in the solution

LRESULT OnParentNotify(UINT nMsg , WPARAM wParam , LPARAM lParam, BOOL& bHandled)
int fwEvent = LOWORD(wParam); // event flags

::OutputDebugString(L"LButton down message");
return OnLButtonDown(WM_LBUTTONDOWN,0,lParam,bHandled);
return 0;

  1. And click on the Bulls Eye control in the contain.htm page in Internet Explorer.
  2. You will see the function OnParentNotify is getting called twice.
  • results in calling the function twice as I saw in customer’s machine
  • once by user32.dll!GetMessageW()
    Second time by user32.dll!PeekMessage

Expected Results:

The OnParentNotify should receive only 1 notification for each click.

Actual Results:

Dev Channel specific:



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    Comments and activity

    • Microsoft Edge Team

      Changed Assigned To to “Kamen M.”

      Changed Assigned To to “Sermet I.”

      Changed Assigned To from “Sermet I.” to “Andy H.”

      Changed Assigned To from “Andy H.” to “IE F.”

      Changed Status to “By design”

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