[Windows] Fix broken table structure for non-unicode code page

go.mod

@@ -4,6 +4,7 @@ go 1.15
 
 require (
 	github.com/jedib0t/go-pretty/v6 v6.0.5
+	github.com/mattn/go-runewidth v0.0.9
 	github.com/muesli/termenv v0.7.2
 	golang.org/x/crypto v0.0.0-20200820211705-5c72a883971a
 	golang.org/x/sys v0.0.0-20200918174421-af09f7315aff

main.go

@@ -29,7 +29,7 @@ var (
 	sortBy   = flag.String("sort", "mountpoint", "sort output by: "+strings.Join(columnIDs(), ", "))
 	width    = flag.Uint("width", 0, "max output width")
 	themeOpt = flag.String("theme", defaultThemeName(), "color themes: dark, light")
-	styleOpt = flag.String("style", "unicode", "style: unicode, ascii")
+	styleOpt = flag.String("style", defaultStyleName(), "style: unicode, ascii")
 
 	inodes     = flag.Bool("inodes", false, "list inode information instead of block usage")
 	jsonOutput = flag.Bool("json", false, "output all devices in JSON format")

style_unix.go

@@ -0,0 +1,7 @@
+// +build !windows
+
+package main
+
+func defaultStyleName() string {
+	return "unicode"
+}

style_windows.go

@@ -0,0 +1,17 @@
+// +build windows
+
+package main
+
+import "github.com/mattn/go-runewidth"
+
+func defaultStyleName() string {
+	/*
+	Due to a bug in github.com/mattn/go-runewidth v0.0.9, the width of unicode rune(such as '╭') could not be correctly
+	calculated.	Degrade to ascii to prevent broken table structure. Remove this once the bug is fixed.
+	 */
+	if runewidth.RuneWidth('╭') > 1 {
+		return "ascii"
+	}
+
+	return "unicode"
+}