When there are no state changes, and no keys pressed on a row, instead of
iterating through a byte bit-by-bit, just fire idle events without checking the
bits. In all other cases, do the bit-walking like we did before.
The reason this is useful is because bit-walking is costly, and slow. If we can
avoid that, we win quite a lot of performance. Since rows being idle is the most
common case on a keyboard, this is a huge net win. Even in the worst case, where
no rows are idle, this is just one byte comparison and a branch slower than our
previous implementation.
As part of this optimization, `actOnHalfRow` was lifted out into its own
function, to reduce code duplication.
Many thanks to @gedankenexperimenter for the original idea!
Signed-off-by: Gergely Nagy <algernon@keyboard.io>
Gergely Nagy
e17869e1a1