To build SciTE for GTK-1.2, be sure to NOT have pkgconfig installed. Having it installed makes the source code assume that you want and have GTK>2.0 installed. 1.60 may be the last version that compiles easily or works right. Later versions may not be fully functional with GTK<2.0. I was able to compile 1.62 and 1.63, but with a bug in the drawing of the border under the tab bar.