just a very littele code style comment:
in setmwfact i dont like the condition checking:
...
if(NULL == arg)
mwfact = MWFACT;
else if(1 == sscanf(arg, "%lf", &delta)) {
...
i prefer (variable == value) to (value == variable), i know that the
later protects against accidental assignment (value = variable will be
an error), but that order is just not logical for me
also the order is not consistent througout the code:
if(ev->request == MappingKeyboard) ...
if(floating != layout->arrange) ...
if(c == sel) ...
make it consistent
i vote for (variable == value)
ymmv
