Don't wait until the line overflows before wrapping it.
Don't wrap the last line.

We must take the indentation into account to compute the number of lines a binary value will use.

Avoid unneeded/redundant calls to lstrcatW() and lstrlenW().
Tighten the scope of variables.

regedit: The xxx_name_len variables track buffer sizes. That is they count the trailing '\0'. Adjust a couple of places that got this wrong and rename them to xxx_name_size.

That is it does not count the trailing '\0'.
Fix a few places that got this wrong and rename it to line_len.