Define own WM message for Message Pump in C++

Question

How do I define my own WM (like WM_CLOSE, etc) message that can be handled by the message pump in C++?

If that is even possible.

Answer 1

It depends on what you are using the message for. This link shows a breakdown of the "address space" for Win32 messages.

WM_USER is not the correct solution in the general case. WM_USER messages "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."

You are better off assigning a message ID that is in the WM_APP range.

RegisterWindowMessage is useful if you want to have the system assign you a message ID at runtime. "All applications that register the same string can use the associated message number for exchanging messages," so you can use RegisterWindowMessage when you need to use a custom message for simple inter-process communication.