fix: measure runes instead of bytes when truncating

There are a couple of gotchas in LipGlossTruncate:

* len() returns the number of bytes in a string
* slicing a string slices it on a byte level

The fix would normally be to convert the string to a slice of runes and
operate on that new slice:

r := []rune(str)

However, reflow already contains an ansi-aware truncate feature that we
can use instead as a drop-in replacement for the LipGlossTruncate
function.

internal/utils/utils.go

@@ -6,14 +6,6 @@ import (
 	"github.com/charmbracelet/lipgloss"
 )
 
-// LipglossTruncate truncates a given line based on its lipgloss width.
-func LipglossTruncate(s string, width int) string {
-	var i int
-	for i = 0; i < len(s) && lipgloss.Width(s[:i]) < width; i++ {
-	} //revive:disable-line:empty-block
-	return s[:i]
-}
-
 // LipglossLengthPadding calculated calculates how much padding a string is given by a style.
 func LipglossPadding(style lipgloss.Style) (int, int) {
 	render := style.Render(" ")

pager/pager.go

@@ -9,8 +9,8 @@ import (
 
 	"github.com/charmbracelet/bubbles/viewport"
 	tea "github.com/charmbracelet/bubbletea"
-	"github.com/charmbracelet/gum/internal/utils"
 	"github.com/charmbracelet/lipgloss"
+	"github.com/muesli/reflow/truncate"
 )
 
 type model struct {
@@ -64,7 +64,7 @@ func (m *model) ProcessText(msg tea.WindowSizeMsg) {
 			text.WriteString(m.lineNumberStyle.Render(fmt.Sprintf("%4d │ ", i+1)))
 		}
 		for m.softWrap && lipgloss.Width(line) > m.maxWidth {
-			truncatedLine := utils.LipglossTruncate(line, m.maxWidth)
+			truncatedLine := truncate.String(line, uint(m.maxWidth))
 			text.WriteString(textStyle.Render(truncatedLine))
 			text.WriteString("\n")
 			if m.showLineNumbers {
@@ -72,7 +72,7 @@ func (m *model) ProcessText(msg tea.WindowSizeMsg) {
 			}
 			line = strings.Replace(line, truncatedLine, "", 1)
 		}
-		text.WriteString(textStyle.Render(utils.LipglossTruncate(line, m.maxWidth)))
+		text.WriteString(textStyle.Render(truncate.String(line, uint(m.maxWidth))))
 		text.WriteString("\n")
 	}
 

pager/search.go

@@ -8,6 +8,7 @@ import (
 	"github.com/charmbracelet/bubbles/textinput"
 	"github.com/charmbracelet/gum/internal/utils"
 	"github.com/charmbracelet/lipgloss"
+	"github.com/muesli/reflow/truncate"
 )
 
 type search struct {
@@ -150,12 +151,12 @@ func softWrapEm(str string, maxWidth int, softWrap bool) string {
 	var text strings.Builder
 	for _, line := range strings.Split(str, "\n") {
 		for softWrap && lipgloss.Width(line) > maxWidth {
-			truncatedLine := utils.LipglossTruncate(line, maxWidth)
+			truncatedLine := truncate.String(line, uint(maxWidth))
 			text.WriteString(truncatedLine)
 			text.WriteString("\n")
 			line = strings.Replace(line, truncatedLine, "", 1)
 		}
-		text.WriteString(utils.LipglossTruncate(line, maxWidth))
+		text.WriteString(truncate.String(line, uint(maxWidth)))
 		text.WriteString("\n")
 	}