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application can process these messages, most applications pass them on tothe DefWindowProc function for default processing. The following listbriefly describes each system message:MessageWM_SYSCHARWM_SYSCOMMANDWM_SYSDEADCHARWM_SYSKEYDOWNWM_SYSKEYUPDescriptionResults when a WM_SYSKEYUP and aWM_SYSKEYDOWN message are translated.Sent when the user selects a command from the Systemmenu.Results when a WM_SYSKEYUP and aWM_SYSKEYDOWN message are translated.Sent when the user holds down the ALT key and thenpresses another key.Sent when the user releases a key that was pressedwhile the ALT key was held down.Clipboard messagesClipboard messages are sent by Windows to an application when otherapplications try to access a window's clipboard. The following list brieflydescribes each clipboard message:MessageWM_ASKCBFORMATNAMEWM_ CHANGECBCHAINWM_DESTROYCLIPBOARDWM_DRA WCLIPBOARDWM_HSCROLLCLIPBOARDWM_P AINTCLIPBOARDWM_RENDERALLFORMATSWM_RENDERFORMATWM_SIZECLIPBOARDWM_ VSCROLLCLIPBOARDDescriptionRequests the name of the CF _ OWNERDISPLAYformat.Notifies viewing-chain members of a change inthe chain.Signals that the contents of the clipboard arebeing destroyed.Signals an application to notify the nextapplication in the chain of a clipboard change.Requests horizontal scrolling for theCF _ OWNERDISPLAY format.Requests painting of the CF _ OWNERDISPLAYformat.Notifies the clipboard owner that it must renderthe clipboard data in all possible formats.Notifies the clipboard owner that it must formatthe last data copied to the clipboard.Notifies the clipboard owner that the clipboardapplication's window size has changed.Requests vertical scrolling for theCF _OWNERDISPLAY format.Chapter 5, Messages overview591