Microsoft KB Archive/247323

= BUG: BN_DOUBLECLICKED Message Handler Not Hit in MFC Dialog Box =

Article ID: 247323

Article Last Modified on 10/17/2003

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APPLIES TO


 * Microsoft Windows CE Toolkit for Visual C++ 6.0, when used with:
 * Microsoft Foundation Class Library 4.2

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This article was previously published under Q247323



SYMPTOMS
On Windows CE using the MFC classes, when you add a BN_DOUBLECLICKED message handler for a button on a dialog box or a window, the handler is not called when the button is double-clicked. The handler is called on Microsoft Windows 95, Microsoft Windows 98, Microsoft Windows NT 4.0, and Microsoft Windows 2000.



CAUSE
This problem is due to a bug in the Windows CE operating system.



RESOLUTION
One possible resolution is to add a BN_CLICKED handler for the button. Inside of the handler, use code similar to the following to test whether the button has been clicked in the last few milliseconds: static BOOL s_bLastClicked = TRUE; static DWORD s_dwTickCount = 0; if (s_bLastClicked) {   DWORD dwTickCount = GetTickCount; if ((dwTickCount - s_dwTickCount) < 500) //Last click less than 500ms? {     s_bLastClicked = FALSE; //Was double-clicked, don't test next time...

//Assume a double click...     //Do your double-click code here... }   s_dwTickCount = dwTickCount; } else s_bLastClicked = TRUE; Manually adding CS_DBLCLKS to the window class style and adding the BS_NOTIFY style for the button does not help. However, this manual process does allow the message to be sent when running on other platforms besides Windows CE.



STATUS
Microsoft has confirmed that this is a bug in the Microsoft products that are listed at the beginning of this article.



Steps to Reproduce Behavior
 Create a new dialog-based application by using the WCE MFC AppWizard. Accept all of the default values and click Finish.  In the OnInitDialog method, add the following code before the return statement: SetClassLong(m_hWnd, GCL_STYLE, GetClassLong(m_hWnd, GCL_STYLE) | CS_DBLCLKS);  Add a button to the dialog box. Right-click the button and click Properties. Click the Styles tab and select the Notify check box. Use ClassWizard by clicking the View menu and selecting the menu item ClassWizard. Under the Object IDs section, click IDC_BUTTON1. Under the Messages section, click the BN_DOUBLECLICKED message. Click Add Function, and then click Edit Code. Place a break point in the BN_DOUBLECLICKED message handler for the button.</li> Build the application and run it when done building.</li></ol>

You should notice that the breakpoint does not get hit when running in the emulator or when running on the device. If you perform the above steps in a Win32 Application not running on Windows CE, the handler works as expected.

Additional query words: CE specific double click WM_LBUTTONDBLCLK BN_CLICKED BN_DOUBLECLICKED WM_LBUTTONDOWN WM_LBUTTONUP

Keywords: kbbug kbbutton KB247323

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