Android default LatinIME handling of hardware keyboard state

Question

I'm trying to make a new Android input method based on the default LatinIME. I want to implement custom behavior that occurs when the hardware keyboard is open or closed. However, looking and searching through the source code for LatinIME I cannot find where the state of the hardware keyboard is checked. I expected it to be handled in onConfigurationChanged() method in the LatinIME class but there's nothing.

Can someone please show me how the default IME knows to hide/show the softkeyboard when I slide out the keyboard on my droid.

Edit: Source link for LatinIME

Thanks!