Windows custom messages Wm_user and Wm_app
Wm_user constants are private messages in Windows Help applications that define private window classes, typically using an integer value of wm_user+, but the total value cannot exceed 0x7fff.
#define Wm_user 0x0400-->1024
The Wm_app constant is a Windows Help application that defines a private message, typically using an integer value of wm_app+, but the total value cannot exceed 0xBFFF.
#define WM_APP 0x8000-->32768
Both of these are defined in the WinUser.h.
Range representation
0 ~ wm_user–1 messages reserved by the operating system.
wm_user ~ 0x7FFF integer-type message for private window class.
Wm_app ~ 0xBFFF messages for Applications.
A string message for 0xc000 ~ 0xFFFF applications.
0xFFFF ~ messages reserved by the operating system.
MFC has pre-defined some common control bars in the afxres.h.
#define AFX_IDW_TOOLBAR 0xe800//main TOOLBAR for window
#define Afx_idw_status_bar 0xe801//STATUS BAR window
#define Afx_idw_preview_bar 0xe802//PrintPreview Dialog BAR
#define Afx_idw_resize_bar 0xe803//OLE in-place RESIZE BAR
#define Afx_idw_rebar 0xe804//COMCTL32 "REBAR" Bar
#define Afx_idw_dialogbar 0xe805//CDialogBar
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Win32 user-defined message range