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How to Process the DTN_WMKEYDOWN Notification

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This topic demonstrates how to process a DTN_WMKEYDOWN notification. Handling this notification code allows the owner of the control to provide specific responses to keystrokes within the callback fields of the control.

What you need to know

Technologies

Prerequisites

  • C/C++
  • Windows User Interface Programming

Instructions

Date and time picker (DTP) controls send the DTN_WMKEYDOWN message to report that the user has typed input in a callback field. If you want to emulate the same keyboard responses that are supported for standard DTP fields or provide custom responses, your application must include code to handle this notification.

The following C++ code example is an application-defined function that processes the DTN_WMKEYDOWN notification.

Security Warning: Using lstrcmp incorrectly can compromise the security of your application. For example, before calling lstrcmp in the following code example, you should make sure the two strings are null-terminated. You should review Security Considerations: Microsoft Windows Controls before continuing.

//  DoWMKeydown increments or decrements the day of month according 
//  to user keyboard input.

void WINAPI DoWMKeydown(
 HWND hwndDP,
 LPNMDATETIMEWMKEYDOWN lpDTKeystroke)
{
    int delta =1;
    if(!lstrcmp(lpDTKeystroke->pszFormat,L"XX")){
        switch(lpDTKeystroke->nVirtKey){
            case VK_DOWN:
            case VK_SUBTRACT:
                delta = -1;  // fall through

            case VK_UP:
            case VK_ADD:
                lpDTKeystroke->st.wDay += (WORD) delta;
                break;
        }
    }
}

Using Date and Time Picker Controls

Date and Time Picker Control Reference

Date and Time Picker