func main() {
X, err := xgb.NewConn()
if err != nil {
log.Fatal(err)
}
// Get the window id of the root window.
setup := xproto.Setup(X)
root := setup.DefaultScreen(X).Root
// Get the atom id (i.e., intern an atom) of "_NET_ACTIVE_WINDOW".
aname := "_NET_ACTIVE_WINDOW"
query1, buf := xproto.InternAtom(X, nil, true, uint16(len(aname)), aname)
activeAtom, err := query1.Reply()
if err != nil {
log.Fatal(err)
}
// Get the atom id (i.e., intern an atom) of "_NET_WM_NAME".
aname = "_NET_WM_NAME"
query2, buf := xproto.InternAtom(X, buf, true, uint16(len(aname)),
aname)
nameAtom, err := query2.Reply()
if err != nil {
log.Fatal(err)
}
// Get the actual value of _NET_ACTIVE_WINDOW.
// Note that 'reply.Value' is just a slice of bytes, so we use an
// XGB helper function, 'Get32', to pull an unsigned 32-bit integer out
// of the byte slice. We then convert it to an X resource id so it can
// be used to get the name of the window in the next GetProperty request.
query3, buf := xproto.GetProperty(X, buf, false, root, activeAtom.Atom,
xproto.GetPropertyTypeAny, 0, (1<<32)-1)
reply, err := query3.Reply()
if err != nil {
log.Fatal(err)
}
windowId := xproto.Window(xgb.Get32(reply.Value))
fmt.Printf("Active window id: %X\n", windowId)
// Now get the value of _NET_WM_NAME for the active window.
// Note that this time, we simply convert the resulting byte slice,
// reply.Value, to a string.
query4, buf := xproto.GetProperty(X, buf, false, windowId, nameAtom.Atom,
xproto.GetPropertyTypeAny, 0, (1<<32)-1)
reply, err = query4.Reply()
if err != nil {
log.Fatal(err)
}
fmt.Printf("Active window name: %s\n", string(reply.Value))
}
// GetProperty abstracts the messiness of calling xgb.GetProperty.
func GetProperty(xu *xgbutil.XUtil, win xproto.Window, atom string) (
*xproto.GetPropertyReply, error) {
atomId, err := Atm(xu, atom)
if err != nil {
return nil, err
}
query, _ := xproto.GetProperty(xu.Conn(), nil, false, win, atomId,
xproto.GetPropertyTypeAny, 0, (1<<32)-1)
reply, err := query.Reply()
if err != nil {
return nil, fmt.Errorf("GetProperty: Error retrieving property '%s' "+
"on window %x: %s", atom, win, err)
}
if reply.Format == 0 {
return nil, fmt.Errorf("GetProperty: No such property '%s' on "+
"window %x.", atom, win)
}
return reply, nil
}