MSPointerDown event cannot be triggered when you use the middle mouse button to scroll in Internet Explorer in Windows 7

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Symptoms

When you use the middle mouse button to scroll in Internet Explorer 10 or Internet Explorer 11 in Windows 7, the MSPointerDownevent cannot be triggered.

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Resolution

Update information

To resolve this issue, install the most recent cumulative security update for Internet Explorer. To do this, go to Microsoft Update.

Notes

This update was first included in the following security update:
2909921 MS14-010: Cumulative security update for Internet Explorer: February 11, 2014
For technical information about the most recent cumulative security update for Internet Explorer, go to the following Microsoft website:
http://www.microsoft.com/technet/security/current.aspx

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More Information

The Reader mode in Internet Explorer 10 creates a new console window handle (HWND) that affects input in WM_MBUTTONUP messages. The MouseHandler function relies on the WM_MBUTTONUP message to clear the _fGotMButtonDownflag flag so that the flag is not cleared. In this situation, the CMouseHandler::IsChordedMouse() function returns true even when the middle mouse button is not down.

Therefore, the mouse handler thinks the behavior is in a chorded state when the left mouse button goes down, and it raises the pointermoveevent instead of the pointerdownor pointerupevent.

This hotfix will reset each button flag on every WM_BUTTONDOWN message. The wParam parameter is used to give the button state from the operating system. The hotfix also fixes many other scenarios in which the main HWND loses capture when buttons are depressed, and the mouse handler state machine breaks, such as the following scenarios: