Linking Golang with XLib

Question

I am trying to use XLib within Go using this code:

package main

// #cgo LDFLAGS: -lX11
// #include <X11/Xlib.h>
import (
    "C"
    "fmt"
)

func main() {
    var dpy = C.XOpenDisplay(nil);
    if dpy == nil {
        panic("Can't open display")
    }

    fmt.Println("%ix%i", C.XDisplayWidth(), C.XDisplayHeight());
}

I'm compiling this via:

go tool cgo $(FILE)

But it results in the following error messages:

1: error: 'XOpenDisplay' undeclared (first use in this function)
1: note: each undeclared identifier is reported only once for each function it appears in
1: error: 'XDisplayWidth' undeclared (first use in this function)
1: error: 'XDisplayHeight' undeclared (first use in this function)

Any idea how to solve this?

Answer 1

cgo is picky about the formatting: you need to keep the "C" import separate, and place the preamble comments immediately above:

package main

// #cgo LDFLAGS: -lX11
// #include <X11/Xlib.h>
import "C"

import (
    "fmt"
)

func main() {

    var dpy = C.XOpenDisplay(nil)
    if dpy == nil {
        panic("Can't open display")
    }

    fmt.Println("%ix%i", C.XDisplayWidth(dpy, 0), C.XDisplayHeight(dpy, 0));
}