Track changes in system time and display resolution

Whenever the system time or the display resolution changes, Windows sends all the top-level windows (forms, in VB jargon) the WM_TIMECHANGE or WM_DISPLAYCHANGE message, respectively. Therefore, you can easily determine when these system-wide settings change by subclassing any form in your application, which is especially useful with the MsgHook DLL.

Using the same method you can also trap other system-wide messages, such as the WM_COMPACTING message, which Windows sends when it’s short on memory:

' REQUIRES THE MSGHOOK.DLL COMPONENT' you can omit the following constant definitions, ' because they are defined in the MsgHook type libraryConst WM_TIMECHANGE = &H1EConst WM_DISPLAYCHANGE = &H7EConst WM_COMPACTING = &H41Dim WithEvents FormHook As MsgHookPrivate Sub Form_Load()    ' start form subclassing with events    Set FormHook = New MsgHook    FormHook.StartSubclass hWndEnd SubPrivate Sub FormHook_AfterMessage(ByVal uMsg As Long, ByVal wParam As Long, _    ByVal lParam As Long, retValue As Long)    Select Case uMsg        Case WM_DISPLAYCHANGE            ' The screen resolution has changed.            ' ...            ' ... (add here your procedure to resize your forms) ...            ' ...        Case WM_TIMECHANGE            ' System date/time has changed.            ' ...        Case WM_COMPACTING            ' Windows is low in memory (release resources if possible).            ' ...            ' ... (release as many resources as possible) ...            ' ...    End SelectEnd Sub

Note that you can indirectly trap this messages also by using the SysInfo.Ocx control, which exposes them as events. Using the subclassing technique outlined here you don’t need any additional component except MsgHook.Dll (which you can use for other subclassing jobs).

Share the Post:
Share on facebook
Share on twitter
Share on linkedin

Related Posts