Windows message handling

Question

4.00/5 (2 votes)

See more:

Is it a good practice for a window to post messages to itself?
If a window sends a message to itself, doesn't that mean that the window procedure gets called recursively?

I am getting confused by the description of SendMessage(): "The function calls the window procedure for the specified window and does not return until the window procedure has processed the message". If this is happening within the same window procedure, the entire thread must be one huge sequence of recursive calls.

Posted 12-Oct-11 8:13am

SMD111

Updated 12-Oct-11 8:49am

v2

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Manfred Rudolf Bihy · Answer 1 · 2011-10-12T08:28:00

It's like this: When a program sends a message to it's own window this is a totally valid operation. Next time the dispatcher checks in the messge loop if there are messages to process, the WindowsProc is called with the corresponding parameters. Recursion that will make your program stop working will only happen if the same message that was received would be resent to its own window. You'll have to be very wary of what you are doing as the recursion might take more than one step:

Received Message | Sent Message
-------------------------------
       A         |      B
       B         |      C
       C         |      A

You can easily spot the loop occuring when any message A, B or C was sent to the windows WndProc.

Best Regards,

—MRB