I’ve tested this on Vanilla mIRC and confirmed the results.

If the user presses the RETURN key with a custom window active, mIRC will produce a windows “beep”. It does this with sounds off, it even does it with picture windows. This is incredibly annoying. My script catches the “Enter” key and uses it as a function for the script. However, every time a user presses enter, it generates a beep.

There does not appear to be a fix, and this bug did not appear in previous versions to 6.xx to my knowledge.

TO REPRODUCE:

Enter the following command:
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/window –p @test
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-> This should produce a custom picture window WITHOUT an edit box, which may produce a beep with no text entered
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Press “Enter”/”Return”
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-> This should produce the annoying unstoppable beep.

There is no editbox, but it beeps anyway!

I've also sent this bug to khaled