Do you use WM_NULL?

[Alex Rest]

I have found funny windows message.
It is described in MSDN so:

WM_NULL
The WM_NULL message performs no operation. An application sends the WM_NULL message if it wants to post a message that the recipient window will ignore.

I propose competition on the best idea how to use it

[ovidiucucu]

Better, read all the documentation before -ing and say "funny".

From MSDN
WM_NULL
[...]
Remarks
For example, if an application has installed a WH_GETMESSAGE hook and wants to prevent a message from being processed, the GetMsgProc callback function can change the message number to WM_NULL so the recipient will ignore it.

As another example, an application can check if a window is responding to messages by sending the WM_NULL message with the SendMessageTimeout function.

[JohnCz]

Originally posted by Alex Rest
I have found funny windows message.
.
.
.
An application sends the WM_NULL message if it wants to post a message that the recipient window will ignore.

I do not see anything funny about that. Just to give you few examples:

This message is used to test if application is still responding and is not hang. Task manager does that by using SendMessageTimeout with WM_NULL.

WM_NULL is also used to filter messages in WH_GETMESSAGE hook. Returning 0 from a hook does not prevent from processing a message. Replacing message with WM_NULL will filter message properly.

Another use is ActiveX control when you decide that it has toolbar and tooltips. Normally application message pump calls PreTranslateMessage; since ActiveX control does not have one, message hook can call PreTranslateMessage and if handled replace original message with WM_NULL.

[Alex Rest]

O!
I am agree.
It is useful.
Thanks for good examples.

[ovidiucucu]

Just joking...
You were like a Java-fan wondering: "What is NULL good for???"


Keep ahead!