Why is a sound played when I press alt-enter on a form?

[yesthatmcgurk]

The subject's the tl;dr version.

The situation is that I'm zooming my form to fullscreen when I hit alt-
enter (kinda like media player behavior). Now my code to go to
fullscreen does not cause the windows "default beep" sound to play.
But when I hit alt-enter on the form that sound is played. And it
only plays when zooming to fullscreen; pressing alt-enter when in
fullscreen does not cause the sound to play.

I've got a tool strip on the form; could it possibly be something to
do with it?

 

[yesthatmcgurk]

The subject's the tl;dr version.

The situation is that I'm zooming my form to fullscreen when I hit alt-
enter (kinda like media player behavior). Now my code to go to
fullscreen does not cause the windows "default beep" sound to play.
But when I hit alt-enter on the form that sound is played. And it
only plays when zooming to fullscreen; pressing alt-enter when in
fullscreen does not cause the sound to play.

I've got a tool strip on the form; could it possibly be something to
do with it?

K, I can figure out that the source of the beep is the toolstrip, as
pressing alt+some key combination that is not available causes the
same beep. I turned on KeyPreview on the form and set the Handled
property to true, but it still beeps. Any ideas?

 

[Guest]

The situation is that I'm zooming my form to fullscreen when I hit alt-

enter (kinda like media player behavior). Now my code to go to
fullscreen does not cause the windows "default beep" sound to play.
But when I hit alt-enter on the form that sound is played. And it
only plays when zooming to fullscreen; pressing alt-enter when in
fullscreen does not cause the sound to play.

In some cases, windows will beep when an Alt+Key menu access fails. You
want to handle Alt+Key inputs, but so does windows, and windows uses Alt to,
for example, give focus to the menu bar. I don't know all the circumstances
where this phenomenon shows up. To read more, search MS for WM_MENUCHAR and
MNC_CLOSE.

This may or may not be your problem. To determine if it is, I think you
need to remove all menus (including system menu) and see if the beeps
continue. If running without menus results in no beeps, then your problem is
the windows beep from a failed menu access key. Note that in full screen
where you don't get beeps, there are presumably no menus in view.

FYI, in my apps, I have decided to live with the beeps rather than try to
stop them. Solving the problem looked messy and like more trouble that it
was worth in my case. If this is your problem and you solve it, please post
back how you solved it.

 

[yesthatmcgurk]

In some cases, windows will beep when an Alt+Key menu access fails. You
want to handle Alt+Key inputs, but so does windows, and windows uses Alt to,
for example, give focus to the menu bar. I don't know all the circumstances
where this phenomenon shows up. To read more, search MS for WM_MENUCHAR and
MNC_CLOSE.

This may or may not be your problem. To determine if it is, I think you
need to remove all menus (including system menu) and see if the beeps
continue. If running without menus results in no beeps, then your problem is
the windows beep from a failed menu access key. Note that in full screen
where you don't get beeps, there are presumably no menus in view.

FYI, in my apps, I have decided to live with the beeps rather than try to
stop them. Solving the problem looked messy and like more trouble that it
was worth in my case. If this is your problem and you solve it, please post
back how you solved it.

K, thanks for the thoughts, I appreciate it. I was actually able to
track it down and stop it.

The beep was being played because the key combination (alt-enter) was
being interpreted as a mnemonic. Since there wasn't a valid control
for that mnemonic to activate, the windows beep sound was being played
to indicate this fact. I wasn't able to figure out exactly who was
playing the sound. It might have even been down in win32 somewhere.
But I did figure out how to stop it.

With the help of http://blogs.msdn.com/jfoscoding/archive/2005/01/24/359334.aspx
I was able to identify a point at which the key combination was being
examined and prevent it from being identified as a mnemonic. The
following override on the form prevents the alt-enter key combination
from being identified as a mnemonic:

protected override bool ProcessDialogKey(Keys keyData)
{
if (keyData == (Keys.Alt | Keys.Enter))
return true;
return base.ProcessDialogKey(keyData);
}

You can use this to prevent any mnemonic combination from beeping by
changing Keys.Enter to whatever other key.