ScreenSaverGracePeriod - how fast can you cross a training room?
We're faced with an issue where presenters are losing their train of thought mid presentation because their slides are covered up by the screensaver - this would not be a significant problem, except that by the time they get back to wiggle the mouse, the workstation has been locked, and they have to type in their password again.
Clearly, we can't make presenters use a machine without workstation locking on the screensaver, or these machines would be accessible for hours under potentially "privileged" accounts. [Note that privilege includes social privilege here - if a VP is presenting, even if they're a restricted user in Windows, any email that comes from them is treated like the word of %deity.]
And I didn't want them finding their own solution (like the "Brandenberg Concerto" solution, where you simply play the Beethoven clip in Windows Media Player, put it on loop, mute the Media Player, and then minimise it), that might simply disable or prevent the screensaver completely, thus avoiding any chance of lockout.
So we found a really creative solution - ScreenSaverGracePeriod.
This is a registry setting - under HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon - that controls how long you have after a screen saver goes active, to wiggle the mouse and get back to your presentation without encountering the workstation lock. [You've probably noticed already that you can wiggle the mouse quickly and not have to re-enter your password.]
It's only a little unfortunate that the documentation incorrectly describes this as a REG_DWORD setting - our own testing shows that it has to be a REG_SZ, even though the contents are a number, describing the number of seconds 'grace' you want. You can use decimal, or hexadecimal if preceded by "0x".
[Aside - why do Microsoft's programmers do this? Surely it's more effort to extract the string and convert it to a number, than have it stored as a number in the first place!]
Note that setting the ScreenSaverGracePeriod to 0 does not disable the workstation lock, it forces it to happen at any point the screensaver goes active, no matter how fast you are. The maximum value is 2,147,483 - seemingly a random number, until you realise that if you express it in thousandths of a second, it's the largest number that can be expressed in a four byte signed integer.