Question

I’m receiving a windows message with code 1092 (0x444) and I don’t know what it is. It’s higher than WM_USER but I searched our code base and found no reference so I don’t think it’s one of ours… does Windows use custom messages above 0x400 and if so how can I look this up?

Answer 1

From the documentanion of WM_USER:

Message numbers in the second range
(WM_USER through 0x7FFF) can be
defined and used by an application to
send messages within a private window
class. These values cannot be used to
define messages that are meaningful
throughout an application, because
some predefined window classes already
define values in this range. For
example, predefined control classes
such as BUTTON, EDIT, LISTBOX, and
COMBOBOX may use these values.
Messages in this range should not be
sent to other applications unless the
applications have been designed to
exchange messages and to attach the
same meaning to the message numbers.

So, that message can be anything.
A quick look in the MFC source code, for example, reveals these definitions

// COMMCTRL.H
#define TB_ADDBUTTONSW        (WM_USER + 68)

// RICHEDIT.H
#define EM_SETCHARFORMAT      (WM_USER + 68)

I searched for 68 because 0x444 = 0x400 + 0x44 = WM_USER + 68