Unfortunately there is no portable way to open an Unicode path with
std::fstream. On *nix, it is enough to call the const char*
constructor. On MSVC, it is enough to call a nonstandard
const wchar_t* constructor. However, on MinGW, there is no way at all
to construct an std::fstream with a wide path, not even using
undocumented APIs. (There used to be a const wchar_t* overload added
back in libstdc++ 4.7, but it got removed for a reason that I was not
able to find out.)
This commit alters the build system substantially; it adds another
platform, `headless`, that provides stubs in place of all GUI
functions, and provides a library `solvespace_headless` alongside
the main executable. To cut down build times, only the few files
that have #if defined(HEADLESS) are built twice for the executable
and the library; the rest is grouped into a new `solvespace_cad`
library. It is not usable on its own and just serves for grouping.
This commit also gates the tests behind a -DENABLE_TESTS=ON CMake
option, ON by default (but suggested as OFF in the README so that
people don't ever have to install cairo to build the executable.)
The tests introduced in this commit are (so far) rudimentary,
although functional, and they serve as a stepping point towards
introducing coverage analysis.
whitequark