About gtk+ homebrew formula

Link the hombrew cairo/include/cairo dir to /opt/X11/include/cairo. Then edit the formula and add
# NEW START
    ENV.append 'LDFLAGS', '-L/usr/local/Cellar/cairo/1.10.2/lib'
    ENV.append 'CPPFLAGS',  '-I/usr/local/Cellar/cairo/1.10.2/include'
# NEW END