feat(adjust-grub-theme): getScreenSizeFromXrandr

try to get primary screen resolution from xrandr

Ref: https://github.com/martyr-deepin/deepin-installer-reborn/blob/b3fa4a16f0634a1c162e5358922c7abfc2798254/hooks/before_chroot/31_get_screen_resolution.job#L6-L22
Ref: linuxdeepin/developer-center#5436

adjust-grub-theme/main.go

@@ -173,6 +173,44 @@ func getScreenSizeFromGrubParams(grubParamsFilePath string) (w, h int, err error
 	return
 }
 
+func getScreenSizeFromXrandr() (w, h int, err error) {
+	out, err = exec.Command("xrandr").Output()
+	if err != nil {
+		return 0, 0, err
+	}
+	// try to get primary screen resolution, for example, extract 1440x900
+	// from "LVDS1 connected primary 1440x900+0+0 (normal left inverted
+	// right x axis y axis)"
+	re := regexp.MustCompile(` connected primary (\d+)x(\d+)`)
+	matches := re.FindStringSubmatch(string(out))
+	if len(matches) == 3 {
+		w, err := strconv.Atoi(matches[1])
+		if err != nil {
+			return 0, 0, err
+		}
+		h := strconv.Atoi(matches[2])
+		if err != nil {
+			return 0, 0, err
+		}
+		return w, h, nil
+	}
+	// if failed, try to get the master screen resolution
+	re = regexp.MustCompile(`Screen 0: .*current (\d+) x (\d+)`)
+	matches := re.FindStringSubmatch(string(out))
+	if len(matches) == 3 {
+		w, err := strconv.Atoi(matches[1])
+		if err != nil {
+			return 0, 0, err
+		}
+		h := strconv.Atoi(matches[2])
+		if err != nil {
+			return 0, 0, err
+		}
+		return w, h, nil
+	}
+	return 0, 0, fmt.Errorf("Failed to extract primary screen resolution")
+}
+
 func cropSaveStyleBox(img image.Image, filenamePrefix string, r int) {
 	imgW := img.Bounds().Dx()
 	imgH := img.Bounds().Dy()
@@ -492,8 +530,12 @@ func main() {
 		optScreenWidth, optScreenHeight, err = getScreenSizeFromGrubParams(grubParamsFile)
 		if err != nil {
 			logger.Debug(err)
-			optScreenWidth = 1024
-			optScreenHeight = 768
+			optScreenWidth, optScreenHeight, err = getScreenSizeFromXrandr()
+			if err != nil {
+				logger.Debug(err)
+				optScreenWidth = 1024
+				optScreenHeight = 768
+			}
 		}
 		logger.Debug("screen width:", optScreenWidth)
 		logger.Debug("screen height:", optScreenHeight)