How to Implement a Mouse Hover/Leave Message on the System Tray

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Introduction

This article illustrates how to implement a tray mouse hover/leave message.

The Problem

Some programs want to get a mouse hover/leave message from the system tray when they want to show a popup window that is not a tool tip. However, the Windows shell doesn’t support it. We can only get mouse move, up, down, and double-click messages from the system tray.

It is very easy to implement a WM_MOUSEHOVER message because the first WM_MOUSEMOVE is that. But, WM_MOUSELEAVE is hard to implement, so I decided to write a compact class to notify the window of a mouse hover/leave message.

The Idea

The basic idea is very simple. It is that no WM_MOUSEMOVE message fires when the mouse is out of the tray icon. This class saves the mouse point whenever a WM_MOUSEMOVE message fires on the system tray, and then another thread compares it with the current mouse point. The thread fires a WM_MOUSELEAVE message when the two points are different.

The following code is the WM_MOUSEMOVE handler.

VOID CTrayPos::OnMouseMove()
{
   EnterCriticalSection(&m_cs);

   GetCursorPos(&m_ptMouse);
   if(m_bTrackMouse == FALSE)
   {
      OnMouseHover();
      m_bTrackMouse = TRUE;
   }

   LeaveCriticalSection(&m_cs);
}

This is a thread function that checks the mouse point.

UINT CALLBACK CTrayPos::TrackMousePt(PVOID pvClass)
{
   POINT       ptMouse;
   CTrayPos    *pTrayPos = (CTrayPos *) pvClass;

   while(WaitForSingleObject(pTrayPos->m_hExitEvent, 2000) ==
                             WAIT_TIMEOUT)
   {

      if(pTrayPos->m_bTrackMouse == TRUE)
      {
         GetCursorPos(&ptMouse);

         if(ptMouse.x != pTrayPos->m_ptMouse.x || ptMouse.y !=
            pTrayPos->m_ptMouse.y)
         {
            pTrayPos->m_bTrackMouse = FALSE;
            pTrayPos->OnMouseLeave();
         }
      }
   }

   return 0;
}

Using the Code

If you want to use this class in your project, just follow these simple steps.

• Add traypos.h and traypos.cpp file to your project.
• Declare a variable of this class like that.
  Note that this class instance exists until the tray icon is deleted, so you must declare it a member variable or a global variable.

CMsgTrayPos traypos;

• Add the following code after the register tray by calling Shell_NotifyIcon.
  The three parameters—hwnd, uID, and uMsgID—are the same value as the member of NOTIFYICONDATA.

traypos.SetNotifyIconInfo(hwnd, uID, uMsgID);

• Call CMsgTrayPos::OnMouseMove on your WM_MOUSEMOVE message handler from the system tray.
• Now, you can add WM_MOUSEHOVER and WM_MOUSELEAVE messages to your tray message handler and write a code there.

CMsgTrayPos API

• VOID CMsgTrayPos::SetNotifyIconInfo(HWND hwnd, UINT uID, UINT uCallbackMsg);
  This function provides tray icon inforamtion to the class. The three parameters—hwnd, uID, and uCallbackMsg—and members of NOTIFYICONDATA are the same.
• VOID CMsgTrayPos::OnMouseMove()

This function is very important. You must call this function when you get a WM_MOUSEMOVE message from the system tray.
This function checks the mouse hover status and updates the mouse point internally.

• BOOL CMsgTrayPos::IsIconHover();
  This function returns the mouse hover status. It returns TRUE if your mouse is on your tray icon.

History

• 22 Aug 2004—Initial upload.