Causes some or all hotkeys to buffer rather than ignore keypresses when their #MaxThreadsPerHotkey limit has been reached.
On: All hotkey subroutines between here and the next #MaxThreadsBuffer ON directive will buffer rather than ignore presses of their hotkeys whenever their subroutines are at their #MaxThreadsPerHotkey limit.
Off: This is the default behavior. A hotkey press will be ignored whenever that hotkey is already running its maximum number of threads (usually 1, but this can be changed with #MaxThreadsPerHotkey).
This directive is rarely used because this type of buffering, which is OFF by default, usually does more harm than good. For example, if you accidentally press a hotkey twice, having this setting ON would cause that hotkey's subroutine to automatically run a second time if its first thread takes less than 1 second to finish (this type of buffer expires after 1 second, by design). Note that AutoHotkey buffers hotkeys in several other ways (such as "Thread Interrupt" and "Critical"). It's just that this particular way can be detrimental, thus it is OFF by default.
The main use for this directive is to increase the responsiveness of the keyboard's auto-repeat feature. For example, when you hold down a hotkey whose #MaxThreadsPerHotkey setting is 1 (the default), incoming keypresses are ignored if that hotkey subroutine is already running. Thus, when the subroutine finishes, it must wait for the next auto-repeat keypress to come in, which might take 50ms or more due to being caught in between keystrokes of the auto-repeat cycle. This 50ms delay can be avoided by enabling this directive for any hotkey that needs the best possible response time while it is being auto-repeated.
As with all # directives, this one should not be positioned in the script as though it were a command (i.e. it is not necessary to have it contained within a subroutine). Instead, position it immediately before the first hotkey label you wish to have affected by it.
#MaxThreads, #MaxThreadsPerHotkey, Critical, Thread (command), Threads, Hotkey, #MaxHotkeysPerInterval, #HotkeyInterval, ListHotkeys
#MaxThreadsBuffer on #x::MsgBox, This hotkey will use this type of buffering. #y::MsgBox, And this one too. #MaxThreadsBuffer off #z::MsgBox, But not this one.