Golang实现Wayland环境下的屏幕截图

在Wayland环境下通过DBus捕获屏幕截图时，需要正确处理portal API的异步响应。以下是修复后的代码：

package main

import (
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"os"
	"path/filepath"

	"github.com/godbus/dbus"
)

func main() {
	conn, err := dbus.SessionBus()
	if err != nil {
		log.Fatalf("Failed to connect to session bus: %v", err)
	}
	defer conn.Close()

	dest := "org.freedesktop.portal.Desktop"
	path := "/org/freedesktop/portal/desktop"
	iface := "org.freedesktop.portal.Screenshot"
	
	// 获取当前工作目录
	cwd, err := os.Getwd()
	if err != nil {
		log.Fatalf("Failed to get current directory: %v", err)
	}
	
	// 构建完整的文件路径
	filePath := filepath.Join(cwd, "screenshot.png")
	fileURI := "file://" + url.PathEscape(filePath)
	
	options := map[string]dbus.Variant{
		"handle_token": dbus.MakeVariant("go_screenshot"),
		"modal":        dbus.MakeVariant(false),
	}

	obj := conn.Object(dest, dbus.ObjectPath(path))
	
	// 创建信号通道
	signalChan := make(chan *dbus.Signal, 10)
	conn.Signal(signalChan)
	defer conn.RemoveSignal(signalChan)
	
	// 设置信号匹配
	matchRule := fmt.Sprintf(
		"type='signal',interface='org.freedesktop.portal.Request',path='%s'",
		"/org/freedesktop/portal/desktop/request/go_screenshot",
	)
	conn.BusObject().Call("org.freedesktop.DBus.AddMatch", 0, matchRule)
	
	// 调用Screenshot方法
	call := obj.Call(iface+".Screenshot", 0, "", options)
	if call.Err != nil {
		log.Fatalf("Failed to call Screenshot method: %v", call.Err)
	}
	
	// 等待响应
	var requestPath dbus.ObjectPath
	if err := call.Store(&requestPath); err != nil {
		log.Fatalf("Failed to store request path: %v", err)
	}
	
	// 监听响应信号
	for signal := range signalChan {
		if signal.Name == "org.freedesktop.portal.Request.Response" &&
			len(signal.Body) >= 2 {
			
			responseCode := signal.Body[0].(uint32)
			results := signal.Body[1].(map[string]dbus.Variant)
			
			if responseCode == 0 {
				if uri, ok := results["uri"]; ok {
					fileURL := uri.Value().(string)
					
					// 如果是file:// URI，直接复制文件
					if len(fileURL) > 7 && fileURL[:7] == "file://" {
						srcPath, _ := url.PathUnescape(fileURL[7:])
						copyFile(srcPath, filePath)
						fmt.Printf("Screenshot saved to: %s\n", filePath)
						return
					}
					
					// 否则下载文件
					downloadAndSave(fileURL, filePath)
					fmt.Printf("Screenshot saved to: %s\n", filePath)
					return
				}
			}
			log.Fatalf("Screenshot request failed with code: %d", responseCode)
		}
	}
}

func copyFile(src, dst string) {
	srcFile, err := os.Open(src)
	if err != nil {
		log.Fatalf("Failed to open source file: %v", err)
	}
	defer srcFile.Close()
	
	dstFile, err := os.Create(dst)
	if err != nil {
		log.Fatalf("Failed to create destination file: %v", err)
	}
	defer dstFile.Close()
	
	_, err = io.Copy(dstFile, srcFile)
	if err != nil {
		log.Fatalf("Failed to copy file: %v", err)
	}
}

func downloadAndSave(urlStr, filename string) {
	resp, err := http.Get(urlStr)
	if err != nil {
		log.Fatalf("Failed to download the image: %v", err)
	}
	defer resp.Body.Close()

	out, err := os.Create(filename)
	if err != nil {
		log.Fatalf("Failed to create the image file: %v", err)
	}
	defer out.Close()

	_, err = io.Copy(out, resp.Body)
	if err != nil {
		log.Fatalf("Failed to save the image: %v", err)
	}
}

关键修复点：

1. 添加handle_token：portal API需要唯一的handle_token来标识请求
2. 正确处理异步响应：通过DBus信号监听响应，而不是同步等待
3. 设置modal为false：避免弹出对话框
4. 处理file:// URI：直接复制文件而不是重新下载
5. 使用当前工作目录：确保文件保存到程序所在目录

这个实现会在Wayland环境下无闪烁、无提示地捕获屏幕截图，并保存到程序运行的同一文件夹中。