pub fn major_version() -> u32
Returns the major version number of the GTK+ library. (e.g. in GTK+ version 3.1.5 this is 3.)
This function is in the library, so it represents the GTK+ library
your code is running against. Contrast with the
macro, which represents the major version of the GTK+ headers you
have included when compiling your code.
the major version number of the GTK+ library