go + cgo与链接

Question

我想使用下面的c作为Go的cgo：

#include <X11/extensions/scrnsaver.h>

main() {
  XScreenSaverInfo *info = XScreenSaverAllocInfo();
  Display *display = XOpenDisplay(0);

  XScreenSaverQueryInfo(display, DefaultRootWindow(display), info);
  printf("%u ms\n", info->idle);
}

用：

gcc -o idle printXIdleTime.c -lX11 -lXss

我重写了Go的cgo代码：

package tools

// #cgo pkg-config: x11
// #include <X11/extensions/scrnsaver.h>
import "C"

func GetIdleTime() (idleTime uint32) {
    var info *C.XScreenSaverInfo
    var display *C.Display 

    info = C.XScreenSaverAllocInfo()
    display = C.XOpenDisplay(0)

    defaultRootWindow := C.XDefaultRootWindow(display)

    C.XScreenSaverQueryInfo(display, defaultRootWindow, info)
    idleTime = info.idle

    return
}

试图用：

go build -gccgoflags="-lXss -lX11"

然而，我得到链接器错误：

/tmp/go-build076004816/opensource.stdk/lib/tools/_obj/x11.cgo2.o: In _cgo_c0e279f6f16e_Cfunc_XScreenSaverAllocInfo': ./x11.go:52: undefined reference toXScreenSaverAllocInfo‘/tmp/go-build076004816/opensource.stdk/lib/tools/_obj/x11.cgo2.o: In function _cgo_c0e279f6f16e_Cfunc_XScreenSaverQueryInfo': ./x11.go:65: undefined reference toXScreenSaverQueryInfo’collect2:错误: ld返回1退出状态

我做错什么了？

Answer 1

这就是我要建造的地方。注意#cgo LDFLAGS行，这可能是您缺少的内容。我不得不做一些其他的改变，以使它的建立。它似乎在我的Linux机器上返回了正确的答案！

package tools

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

func GetIdleTime() (idleTime uint32) {
    var info *C.XScreenSaverInfo
    var display *C.Display

    info = C.XScreenSaverAllocInfo()
    display = C.XOpenDisplay(nil)

    defaultRootWindow := C.XDefaultRootWindow(display)

    C.XScreenSaverQueryInfo(display, C.Drawable(defaultRootWindow), info)
    idleTime = uint32(info.idle)

    return
}

Answer 2

请注意，这可以通过本机X Go结合和ScreenSaver扩展来完成：

package main

import (
    "fmt"
    "log"

    "github.com/BurntSushi/xgb"
    "github.com/BurntSushi/xgb/xproto"
    "github.com/BurntSushi/xgb/screensaver"
)

func main() {
    X, err := xgb.NewConn()
    if err != nil {
        log.Fatal(err)
    }

    if err = screensaver.Init(X); err != nil {
        log.Fatal(err)
    }

    root := xproto.Setup(X).DefaultScreen(X).Root
    info, err := screensaver.QueryInfo(X, xproto.Drawable(root)).Reply()
    if err != nil {
        log.Fatal(err)
    }

    fmt.Printf("Idle: %d\n", info.MsSinceUserInput)
}

产出：

[andrew@Liger go] go run xscreensaver_idle.go 
Idle: 1040