msglist: refactor tree building

Our way of building trees seems absurd: generate a list of prefixes,
reverse it, and trim the first element.

Change it so the string is built back to front and define the arrows
beforehand so they are easier to configure.

Signed-off-by: Moritz Poldrack <git@moritz.sh>
Acked-by: Robin Jarry <robin@jarry.cc>
Tested-by: Inwit <inwit@sindominio.net>

1 files changed, 26 insertions, 35 deletions

diff --git a/app/msglist.go b/app/msglist.go
index 40253ed6..7948e6a1 100644
--- a/app/msglist.go
+++ b/app/msglist.go
@@ -2,13 +2,13 @@ package app
 
 import (
 	"bytes"
-	"fmt"
 	"math"
 	"strings"
 
 	sortthread "github.com/emersion/go-imap-sortthread"
 	"github.com/emersion/go-message/mail"
 	"github.com/gdamore/tcell/v2"
+	"github.com/mattn/go-runewidth"
 
 	"git.sr.ht/~rjarry/aerc/config"
 	"git.sr.ht/~rjarry/aerc/lib"
@@ -419,43 +419,34 @@ func unreadInThread(thread *types.Thread, store *lib.MessageStore) (ctr int) {
 
 func threadPrefix(t *types.Thread, reverse bool, point bool) string {
 	var arrow string
-	if t.Parent != nil {
-		switch {
-		case t.NextSibling != nil:
-			arrow = "├─"
-		case reverse:
-			arrow = "┌─"
-		default:
-			arrow = "└─"
-		}
-		if point {
-			arrow += ">"
-		}
-	}
-	var prefix []string
-	for n := t; n.Parent != nil; n = n.Parent {
-		switch {
-		case n.Parent.NextSibling != nil && point:
-			prefix = append(prefix, "│  ")
-		case n.Parent.NextSibling != nil:
-			prefix = append(prefix, "│ ")
-		case point:
-			prefix = append(prefix, "   ")
-		default:
-			prefix = append(prefix, "  ")
+	var tip string
+	if point {
+		tip = ">"
+	}
+	arrowPrefixSibling := "├─" + tip
+	arrowPrefixReverse := "┌─" + tip
+	arrowPrefixEnd := "└─" + tip
+	arrowStem := "│"
+	arrowIndent := strings.Repeat(" ", runewidth.StringWidth(arrowPrefixSibling)-1)
+
+	switch {
+	case t.Parent != nil && t.NextSibling != nil:
+		arrow += arrowPrefixSibling
+	case t.Parent != nil && reverse:
+		arrow += arrowPrefixReverse
+	case t.Parent != nil:
+		arrow += arrowPrefixEnd
+	}
+
+	for n := t.Parent; n != nil && n.Parent != nil; n = n.Parent {
+		if n.NextSibling != nil {
+			arrow = arrowStem + arrowIndent + arrow
+		} else {
+			arrow = " " + arrowIndent + arrow
 		}
 	}
-	// prefix is now in a reverse order (inside --> outside), so turn it
-	for i, j := 0, len(prefix)-1; i < j; i, j = i+1, j-1 {
-		prefix[i], prefix[j] = prefix[j], prefix[i]
-	}
 
-	// we don't want to indent the first child, hence we strip that level
-	if len(prefix) > 0 {
-		prefix = prefix[1:]
-	}
-	ps := strings.Join(prefix, "")
-	return fmt.Sprintf("%v%v", ps, arrow)
+	return arrow
 }
 
 func sameParent(left, right *types.Thread) bool {