OMNIS-39: Edit TUI text fields by grapheme cluster

CHANGELOG.md

@@ -4,6 +4,11 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## [Unreleased]
 
+### Fixed
+- `omnishell tui`: the filter and option-value fields move the cursor and
+  delete by grapheme cluster, so a combining accent, an emoji sequence or a flag
+  is handled as one character.
+
 ## [0.7.0] - 2026-10-07
 
 ### Added

go.mod

@@ -8,6 +8,7 @@ require (
 	github.com/BurntSushi/toml v1.6.0
 	github.com/charmbracelet/x/ansi v0.11.8
 	github.com/charmbracelet/x/term v0.2.2
+	github.com/rivo/uniseg v0.4.7
 	github.com/spf13/cobra v1.10.2
 )
 
@@ -23,7 +24,6 @@ require (
 	github.com/lucasb-eyer/go-colorful v1.4.1 // indirect
 	github.com/mattn/go-runewidth v0.0.24 // indirect
 	github.com/muesli/cancelreader v0.2.2 // indirect
-	github.com/rivo/uniseg v0.4.7 // indirect
 	github.com/russross/blackfriday/v2 v2.1.0 // indirect
 	github.com/spf13/pflag v1.0.9 // indirect
 	github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e // indirect

internal/tui/textedit.go

@@ -3,35 +3,77 @@ package tui
 import (
 	tea "charm.land/bubbletea/v2"
 	"github.com/charmbracelet/x/ansi"
+	"github.com/rivo/uniseg"
 )
 
 // The two text fields (the filter and an option value) keep their text as a
 // string and the cursor as a rune index into it, so the Model stays a plain
-// value and tests can read the text directly.
+// value and tests can read the text directly. The cursor always rests on a
+// grapheme-cluster boundary: a visible character made of several runes (a
+// combining accent, a ZWJ emoji, a flag) is moved over and deleted as one.
+
+// clusterStarts returns the rune index at which each grapheme cluster of runes
+// starts, followed by len(runes) as the final boundary.
+func clusterStarts(runes []rune) []int {
+	starts := make([]int, 0, len(runes)+1)
+	rest, offset := string(runes), 0
+	for rest != "" {
+		cluster, remainder, _, _ := uniseg.FirstGraphemeClusterInString(rest, -1)
+		starts = append(starts, offset)
+		offset += len([]rune(cluster))
+		rest = remainder
+	}
+	return append(starts, len(runes))
+}
+
+// snapToBoundary returns the cluster boundary at or before pos, which it first
+// clamps into the text.
+func snapToBoundary(starts []int, pos int) int {
+	pos = min(max(pos, 0), starts[len(starts)-1])
+	for i := len(starts) - 1; i >= 0; i-- {
+		if starts[i] <= pos {
+			return starts[i]
+		}
+	}
+	return 0
+}
+
+// boundaryIndex returns the index into starts of the boundary pos (already
+// snapped).
+func boundaryIndex(starts []int, pos int) int {
+	for i, s := range starts {
+		if s == pos {
+			return i
+		}
+	}
+	return len(starts) - 1
+}
 
 // editText applies one key press to text, with the cursor at pos, and returns
 // the new text and cursor. ok is false for keys it does not handle, so the
 // caller can give them their own meaning (enter, esc, ctrl+c).
 func editText(text string, pos int, msg tea.KeyPressMsg) (string, int, bool) {
 	runes := []rune(text)
-	pos = min(max(pos, 0), len(runes))
+	starts := clusterStarts(runes)
+	pos = snapToBoundary(starts, pos)
+	at := boundaryIndex(starts, pos)
 	switch msg.String() {
 	case "left", "ctrl+b":
-		pos = max(pos-1, 0)
+		pos = starts[max(at-1, 0)]
 	case "right", "ctrl+f":
-		pos = min(pos+1, len(runes))
+		pos = starts[min(at+1, len(starts)-1)]
 	case "home", "ctrl+a":
 		pos = 0
 	case "end", "ctrl+e":
 		pos = len(runes)
 	case "backspace":
-		if pos > 0 {
-			runes = append(runes[:pos-1], runes[pos:]...)
-			pos--
+		if at > 0 {
+			runes = append(runes[:starts[at-1]], runes[pos:]...)
+			pos = starts[at-1]
 		}
 	case "delete", "ctrl+d":
-		if pos < len(runes) {
-			runes = append(runes[:pos], runes[pos+1:]...)
+		if at < len(starts)-1 {
+			runes = append(runes[:pos], runes[starts[at+1]:]...)
 		}
 	default:
 		if msg.Text == "" {
@@ -47,7 +89,7 @@ func editText(text string, pos int, msg tea.KeyPressMsg) (string, int, bool) {
 // the new text and the cursor behind the inserted part.
 func pasteText(text string, pos int, content string) (string, int) {
 	runes := []rune(text)
-	pos = min(max(pos, 0), len(runes))
+	pos = snapToBoundary(clusterStarts(runes), pos)
 	add := []rune(sanitize(content))
 	out := make([]rune, 0, len(runes)+len(add))
 	out = append(out, runes[:pos]...)
@@ -62,7 +104,7 @@ func pasteText(text string, pos int, content string) (string, int) {
 // right when much of it follows the cursor, so the cursor is always inside.
 func editWindow(text string, pos, room int) (string, int) {
 	runes := []rune(text)
-	pos = min(max(pos, 0), len(runes))
+	pos = snapToBoundary(clusterStarts(runes), pos)
 	before, after := string(runes[:pos]), string(runes[pos:])
 	atEnd := after == ""
 

internal/tui/textedit_test.go

@@ -269,3 +269,92 @@ func TestNoCursorOutsideTextFields(t *testing.T) {
 		t.Fatal("a kept filter has no cursor")
 	}
 }
+
+// Clusters made of several runes, written as escapes so the source stays
+// unambiguous: e + combining acute, a ZWJ family emoji, and a flag.
+const (
+	clusterAccent = "e\u0301"
+	clusterFamily = "\U0001F468\u200d\U0001F469\u200d\U0001F467"
+	clusterFlag   = "\U0001F1E9\U0001F1EA"
+)
+
+func TestEditTextMovesOverWholeClusters(t *testing.T) {
+	for name, cluster := range map[string]string{"accent": clusterAccent, "family": clusterFamily, "flag": clusterFlag} {
+		text := "a" + cluster + "z"
+		end := len([]rune(text))
+		afterCluster := end - 1
+
+		_, pos, _ := editText(text, afterCluster, key("left"))
+		if pos != 1 {
+			t.Errorf("%s: left from behind the cluster gave pos %d, want 1", name, pos)
+		}
+		_, pos, _ = editText(text, 1, key("right"))
+		if pos != afterCluster {
+			t.Errorf("%s: right over the cluster gave pos %d, want %d", name, pos, afterCluster)
+		}
+	}
+}
+
+func TestEditTextDeletesWholeClusters(t *testing.T) {
+	for name, cluster := range map[string]string{"accent": clusterAccent, "family": clusterFamily, "flag": clusterFlag} {
+		text := "a" + cluster + "z"
+		afterCluster := len([]rune(text)) - 1
+
+		got, pos, _ := editText(text, afterCluster, key("backspace"))
+		if got != "az" || pos != 1 {
+			t.Errorf("%s: backspace gave text=%q pos=%d, want az / 1", name, got, pos)
+		}
+		got, pos, _ = editText(text, 1, key("delete"))
+		if got != "az" || pos != 1 {
+			t.Errorf("%s: delete gave text=%q pos=%d, want az / 1", name, got, pos)
+		}
+	}
+}
+
+func TestEditTextSnapsAMidClusterCursorToABoundary(t *testing.T) {
+	text := "a" + clusterFamily + "z"
+	_, pos, _ := editText(text, 3, key("right")) // 3 is inside the family emoji
+	if pos != len([]rune(text))-1 {
+		t.Fatalf("pos = %d, want the cursor behind the cluster", pos)
+	}
+	got, pos, _ := editText(text, 3, key("delete"))
+	if got != "az" || pos != 1 {
+		t.Fatalf("text=%q pos=%d, want the whole cluster removed", got, pos)
+	}
+}
+
+func TestPasteTextSnapsAMidClusterCursorToABoundary(t *testing.T) {
+	got, pos := pasteText("a"+clusterAccent+"z", 2, "X") // between e and the accent
+	if got != "aXe\u0301z" || pos != 2 {
+		t.Fatalf("text=%q pos=%d, want X before the cluster, never inside it", got, pos)
+	}
+}
+
+func TestEditWindowNeverCutsACluster(t *testing.T) {
+	for name, cluster := range map[string]string{"accent": clusterAccent, "family": clusterFamily, "flag": clusterFlag} {
+		text := strings.Repeat("ab"+cluster, 12)
+		runes := []rune(text)
+		for pos := 0; pos <= len(runes); pos++ {
+			cell, col := editWindow(text, pos, 9)
+			if w := ansi.StringWidth(cell); w > 9 || col < 0 || col >= 9 {
+				t.Fatalf("%s pos %d: cell %q is %d wide with cursor at %d", name, pos, cell, w, col)
+			}
+			for _, bad := range []string{"\u0301", "\u200d"} {
+				if strings.HasPrefix(strings.TrimPrefix(cell, "…"), bad) {
+					t.Fatalf("%s pos %d: cell %q starts inside a cluster", name, pos, cell)
+				}
+			}
+			if strings.Count(cell, "\U0001F1E9")+strings.Count(cell, "\U0001F1EA") == 1 {
+				t.Fatalf("%s pos %d: cell %q holds half a flag", name, pos, cell)
+			}
+		}
+	}
+}
+
+func TestEditWindowPlacesTheCursorOnAClusterColumn(t *testing.T) {
+	text := "a" + clusterAccent + "z"
+	cell, col := editWindow(text, 2, 23) // mid-cluster input snaps to the boundary
+	if cell != text || col != 1 {
+		t.Fatalf("cell=%q col=%d, want the cursor on the accent cluster at column 1", cell, col)
+	}
+}