I suppose the following is not the expected result. Any hint what to do?
Code:
# pkg-config --cflags gtk+-3.0
Package xproto was not found in the pkg-config search path.
Perhaps you should add the directory containing `xproto.pc'
to the PKG_CONFIG_PATH environment variable
Package 'xproto', required by 'x11', not found
Package 'kbproto', required by 'x11', not found
Package 'xextproto', required by 'xext', not found
Package 'xproto', required by 'xdamage', not found
Package 'damageproto', required by 'xdamage', not found
Package 'xproto', required by 'xfixes', not found
Package 'fixesproto', required by 'xfixes', not found
Package 'xproto', required by 'xfixes', not found
Package 'fixesproto', required by 'xfixes', not found
Package 'xproto', required by 'x11', not found
Package 'kbproto', required by 'x11', not found
Package 'xproto', required by 'xau', not found
Package 'xproto', required by 'xdmcp', not found
Package 'xproto', required by 'xau', not found
Package 'xproto', required by 'xdmcp', not found
...
...