In principle, GTK3 is the way forward, and GTK2 is officially
deprecated, though still maintained. In practice however, GTK3
is often unbearably buggy; e.g. on my system, combo boxes
don't ever roll up in GTK3 windows. So I have added support
for both.
This required a few minor changes to the core, namely:
* GTK wants to know beforehand whether a menu item is a check
menu item or a regular one.
* GTK doesn't give us an easy way to execute something after
any event is processed, so an explicit idle timer is added.
This is a no-op on Win32.
* A few function signatures were const'ed, since GTK expects
immutable strings when converting to Glib::ustring.
Microsoft defines an RGB() macro that at one point was compatible with our
version (returning a packed integer containing 8-bit red, green and blue
channels), but is no longer, and the incompatibility led to an awkward
situation in w32main.cpp where we had to restore Microsoft's form of the
macro in order for the commctrl.h header to compile. By renaming the macro
to RGBi()---analogous to the RGBf() macro we already define---we avoid the
hassle entirely.
The SolveSpace top-level directory was getting a bit cluttered, so
following the example of numerous other free-software projects, we move the
main application source into a subdirectory and adjust the build systems
accordingly.
Also, got rid of the obj/ directory in favor of creating it on the fly in
Makefile.msvc.