x-backspace-delete-keys-p

x-backspace-delete-keys-p is a built-in function in `C source code'.

(x-backspace-delete-keys-p &optional FRAME)

Check if both Backspace and Delete keys are on the keyboard of FRAME.
FRAME nil means use the selected frame.
Value is t if we know that both keys are present, and are mapped to the
usual X keysyms. Value is `lambda' if we cannot determine if both keys are
present and mapped to the usual X keysyms.