Use utils.StringWidth to optimize rendering performance

runewidth.StringWidth is an expensive call, even if the input string is pure
ASCII. Improve this by providing a wrapper that short-circuits the call to len
if the input is ASCII.

Benchmark results show that for non-ASCII strings it makes no noticable
difference, but for ASCII strings it provides a more than 200x speedup.

BenchmarkStringWidthAsciiOriginal-10            718135       1637 ns/op
BenchmarkStringWidthAsciiOptimized-10        159197538          7.545 ns/op
BenchmarkStringWidthNonAsciiOriginal-10         486290       2391 ns/op
BenchmarkStringWidthNonAsciiOptimized-10        502286       2383 ns/op

pkg/gui/controllers/helpers/window_arrangement_helper.go

@@ -8,7 +8,6 @@ import (
 	"github.com/jesseduffield/lazygit/pkg/config"
 	"github.com/jesseduffield/lazygit/pkg/gui/types"
 	"github.com/jesseduffield/lazygit/pkg/utils"
-	"github.com/mattn/go-runewidth"
 	"golang.org/x/exp/slices"
 )
 
@@ -272,7 +271,7 @@ func infoSectionChildren(args WindowArrangementArgs) []*boxlayout.Box {
 		return []*boxlayout.Box{
 			{
 				Window: "searchPrefix",
-				Size:   runewidth.StringWidth(args.SearchPrefix),
+				Size:   utils.StringWidth(args.SearchPrefix),
 			},
 			{
 				Window: "search",
@@ -325,7 +324,7 @@ func infoSectionChildren(args WindowArrangementArgs) []*boxlayout.Box {
 		// app status appears very briefly in demos and dislodges the caption,
 		// so better not to show it at all
 		if args.AppStatus != "" {
-			result = append(result, &boxlayout.Box{Window: "appStatus", Size: runewidth.StringWidth(args.AppStatus)})
+			result = append(result, &boxlayout.Box{Window: "appStatus", Size: utils.StringWidth(args.AppStatus)})
 		}
 	}
 
@@ -338,7 +337,7 @@ func infoSectionChildren(args WindowArrangementArgs) []*boxlayout.Box {
 			&boxlayout.Box{
 				Window: "information",
 				// unlike appStatus, informationStr has various colors so we need to decolorise before taking the length
-				Size: runewidth.StringWidth(utils.Decolorise(args.InformationStr)),
+				Size: utils.StringWidth(utils.Decolorise(args.InformationStr)),
 			})
 	}
 

pkg/gui/information_panel.go

@@ -6,7 +6,6 @@ import (
 	"github.com/jesseduffield/lazygit/pkg/constants"
 	"github.com/jesseduffield/lazygit/pkg/gui/style"
 	"github.com/jesseduffield/lazygit/pkg/utils"
-	"github.com/mattn/go-runewidth"
 )
 
 func (gui *Gui) informationStr() string {
@@ -34,7 +33,7 @@ func (gui *Gui) handleInfoClick() error {
 	width, _ := view.Size()
 
 	if activeMode, ok := gui.helpers.Mode.GetActiveMode(); ok {
-		if width-cx > runewidth.StringWidth(gui.c.Tr.ResetInParentheses) {
+		if width-cx > utils.StringWidth(gui.c.Tr.ResetInParentheses) {
 			return nil
 		}
 		return activeMode.Reset()
@@ -43,10 +42,10 @@ func (gui *Gui) handleInfoClick() error {
 	var title, url string
 
 	// if we're not in an active mode we show the donate button
-	if cx <= runewidth.StringWidth(gui.c.Tr.Donate) {
+	if cx <= utils.StringWidth(gui.c.Tr.Donate) {
 		url = constants.Links.Donate
 		title = gui.c.Tr.Donate
-	} else if cx <= runewidth.StringWidth(gui.c.Tr.Donate)+1+runewidth.StringWidth(gui.c.Tr.AskQuestion) {
+	} else if cx <= utils.StringWidth(gui.c.Tr.Donate)+1+utils.StringWidth(gui.c.Tr.AskQuestion) {
 		url = constants.Links.Discussions
 		title = gui.c.Tr.AskQuestion
 	}

pkg/gui/presentation/branches.go

@@ -56,7 +56,7 @@ func getBranchDisplayStrings(
 	// Recency is always three characters, plus one for the space
 	availableWidth := viewWidth - 4
 	if len(branchStatus) > 0 {
-		availableWidth -= runewidth.StringWidth(utils.Decolorise(branchStatus)) + 1
+		availableWidth -= utils.StringWidth(utils.Decolorise(branchStatus)) + 1
 	}
 	if icons.IsIconEnabled() {
 		availableWidth -= 2 // one for the icon, one for the space
@@ -65,7 +65,7 @@ func getBranchDisplayStrings(
 		availableWidth -= utils.COMMIT_HASH_SHORT_SIZE + 1
 	}
 	if checkedOutByWorkTree {
-		availableWidth -= runewidth.StringWidth(worktreeIcon) + 1
+		availableWidth -= utils.StringWidth(worktreeIcon) + 1
 	}
 
 	displayName := b.Name
@@ -79,7 +79,7 @@ func getBranchDisplayStrings(
 	}
 
 	// Don't bother shortening branch names that are already 3 characters or less
-	if runewidth.StringWidth(displayName) > max(availableWidth, 3) {
+	if utils.StringWidth(displayName) > max(availableWidth, 3) {
 		// Never shorten the branch name to less then 3 characters
 		len := max(availableWidth, 4)
 		displayName = runewidth.Truncate(displayName, len, "…")

pkg/utils/formatting.go

@@ -3,6 +3,7 @@ package utils
 import (
 	"fmt"
 	"strings"
+	"unicode"
 
 	"github.com/mattn/go-runewidth"
 	"github.com/samber/lo"
@@ -21,10 +22,22 @@ type ColumnConfig struct {
 	Alignment Alignment
 }
 
+func StringWidth(s string) int {
+	// We are intentionally not using a range loop here, because that would
+	// convert the characters to runes, which is unnecessary work in this case.
+	for i := 0; i < len(s); i++ {
+		if s[i] > unicode.MaxASCII {
+			return runewidth.StringWidth(s)
+		}
+	}
+
+	return len(s)
+}
+
 // WithPadding pads a string as much as you want
 func WithPadding(str string, padding int, alignment Alignment) string {
 	uncoloredStr := Decolorise(str)
-	width := runewidth.StringWidth(uncoloredStr)
+	width := StringWidth(uncoloredStr)
 	if padding < width {
 		return str
 	}
@@ -144,7 +157,7 @@ func getPadWidths(stringArrays [][]string) []int {
 		return MaxFn(stringArrays, func(stringArray []string) int {
 			uncoloredStr := Decolorise(stringArray[i])
 
-			return runewidth.StringWidth(uncoloredStr)
+			return StringWidth(uncoloredStr)
 		})
 	})
 }
@@ -161,7 +174,7 @@ func MaxFn[T any](items []T, fn func(T) int) int {
 
 // TruncateWithEllipsis returns a string, truncated to a certain length, with an ellipsis
 func TruncateWithEllipsis(str string, limit int) string {
-	if runewidth.StringWidth(str) > limit && limit <= 2 {
+	if StringWidth(str) > limit && limit <= 2 {
 		return strings.Repeat(".", limit)
 	}
 	return runewidth.Truncate(str, limit, "…")

pkg/utils/formatting_test.go

@@ -4,6 +4,7 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/mattn/go-runewidth"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -250,3 +251,27 @@ func TestRenderDisplayStrings(t *testing.T) {
 		assert.EqualValues(t, test.expectedColumnPositions, columnPositions)
 	}
 }
+
+func BenchmarkStringWidthAsciiOriginal(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		runewidth.StringWidth("some ASCII string")
+	}
+}
+
+func BenchmarkStringWidthAsciiOptimized(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		StringWidth("some ASCII string")
+	}
+}
+
+func BenchmarkStringWidthNonAsciiOriginal(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		runewidth.StringWidth("some non-ASCII string 🍉")
+	}
+}
+
+func BenchmarkStringWidthNonAsciiOptimized(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		StringWidth("some non-ASCII string 🍉")
+	}
+}