Fix fullwidth rune handling.

src/utils/runes.go

@@ -0,0 +1,24 @@
+package utils
+
+import (
+	rw "github.com/mattn/go-runewidth"
+)
+
+func TruncateFront(s string, w int, prefix string) string {
+	if rw.StringWidth(s) <= w {
+		return s
+	}
+	r := []rune(s)
+	pw := rw.StringWidth(prefix)
+	w -= pw
+	width := 0
+	i := len(r) - 1
+	for ; i >= 0; i-- {
+		cw := rw.RuneWidth(r[i])
+		width += cw
+		if width > w {
+			break
+		}
+	}
+	return prefix + string(r[i+1:len(r)])
+}

src/utils/runes_test.go

@@ -0,0 +1,50 @@
+package utils
+
+import "testing"
+
+const (
+	ELLIPSIS = "…"
+)
+
+func TestTruncateFront(t *testing.T) {
+	tests := []struct {
+		s      string
+		w      int
+		prefix string
+		want   string
+	}{
+		{"", 0, ELLIPSIS, ""},
+		{"", 1, ELLIPSIS, ""},
+		{"", 10, ELLIPSIS, ""},
+
+		{"abcdef", 0, ELLIPSIS, ELLIPSIS},
+		{"abcdef", 1, ELLIPSIS, ELLIPSIS},
+		{"abcdef", 2, ELLIPSIS, ELLIPSIS + "f"},
+		{"abcdef", 5, ELLIPSIS, ELLIPSIS + "cdef"},
+		{"abcdef", 6, ELLIPSIS, "abcdef"},
+		{"abcdef", 10, ELLIPSIS, "abcdef"},
+
+		{"abcdef", 0, "...", "..."},
+		{"abcdef", 1, "...", "..."},
+		{"abcdef", 3, "...", "..."},
+		{"abcdef", 4, "...", "...f"},
+		{"abcdef", 5, "...", "...ef"},
+		{"abcdef", 6, "...", "abcdef"},
+		{"abcdef", 10, "...", "abcdef"},
+
+		{"｟full～width｠", 15, ".", "｟full～width｠"},
+		{"｟full～width｠", 14, ".", ".full～width｠"},
+		{"｟full～width｠", 13, ".", ".ull～width｠"},
+		{"｟full～width｠", 10, ".", ".～width｠"},
+		{"｟full～width｠", 9, ".", ".width｠"},
+		{"｟full～width｠", 8, ".", ".width｠"},
+		{"｟full～width｠", 3, ".", ".｠"},
+		{"｟full～width｠", 2, ".", "."},
+	}
+
+	for _, test := range tests {
+		if got := TruncateFront(test.s, test.w, test.prefix); got != test.want {
+			t.Errorf("TruncateFront(%q, %d, %q) = %q; want %q", test.s, test.w, test.prefix, got, test.want)
+		}
+	}
+}

src/widgets/proc.go

@@ -16,6 +16,7 @@ import (
 	ui "github.com/cjbassi/gotop/src/termui"
 	"github.com/cjbassi/gotop/src/utils"
 	tui "github.com/gizak/termui/v3"
+	rw "github.com/mattn/go-runewidth"
 )
 
 const (
@@ -123,7 +124,8 @@ func (self *ProcWidget) HandleEvent(e tui.Event) bool {
 		self.SetEditingFilter(false)
 	case "<Backspace>":
 		if self.filter != "" {
-			self.filter = self.filter[:len(self.filter)-1]
+			r := []rune(self.filter)
+			self.filter = string(r[:len(r)-1])
 			self.update()
 		}
 	case "<Space>":
@@ -143,6 +145,8 @@ func (self *ProcWidget) Draw(buf *tui.Buffer) {
 }
 
 func (self *ProcWidget) drawFilter(buf *tui.Buffer) {
+	padding := 2
+
 	style := self.TitleStyle
 	label := " Filter: "
 	if self.editingFilter {
@@ -151,24 +155,34 @@ func (self *ProcWidget) drawFilter(buf *tui.Buffer) {
 	}
 	cursorStyle := tui.NewStyle(style.Bg, style.Fg, tui.ModifierClear)
 
-	p := image.Pt(self.Min.X+2, self.Max.Y-1)
+	p := image.Pt(self.Min.X+padding, self.Max.Y-1)
 	buf.SetString(label, style, p)
-	p.X += utf8.RuneCountInString(label)
+	p.X += rw.StringWidth(label)
 
-	maxLen := self.Max.X - p.X - 5
-	filter := self.filter
-	if l := utf8.RuneCountInString(filter); l > maxLen {
-		filter = ELLIPSIS + filter[l-maxLen+1:]
+	tail := " "
+	if self.editingFilter {
+		tail = "] "
 	}
+
+	maxLen := self.Max.X - p.X - padding - rw.StringWidth(tail)
+	if self.editingFilter {
+		maxLen -= 1 // for cursor
+	}
+
+	filter := utils.TruncateFront(self.filter, maxLen, ELLIPSIS)
 	buf.SetString(filter, self.TitleStyle, p)
-	p.X += utf8.RuneCountInString(filter)
+	p.X += rw.StringWidth(filter)
 
 	if self.editingFilter {
 		buf.SetString(CURSOR, cursorStyle, p)
-		p.X += 1
-		remaining := self.Max.X - 2 - p.X
-		buf.SetString(fmt.Sprintf("%*s", remaining, "] "), style, p)
+		p.X += rw.StringWidth(CURSOR)
+
+		if remaining := maxLen - rw.StringWidth(filter); remaining > 0 {
+			buf.SetString(strings.Repeat(" ", remaining), self.TitleStyle, p)
+			p.X += remaining
+		}
 	}
+	buf.SetString(tail, style, p)
 }
 
 func (self *ProcWidget) filterProcs(procs []Proc) []Proc {