tui: strip ANSI from prompt before wrapping so cursor lands at end

When the interactive editor's Prompt carried ANSI styling — the
themed "▌ " glyph that interactive mode builds via
cfg.Theme.AccentBar — the raw escape bytes leaked into wrapLine's
per-rune width counter. Each byte of the SGR sequence (ESC, '[',
digits, ';', 'm') reported runewidth 1, so an 11-byte color escape
inflated the perceived prompt width by ~10 cells. wrapLine then
made wrap decisions against that inflated width, locateCursor
walked the inflated bodies, and Render() returned a cursor column
that landed inside the wrapped row instead of at its visible end.

The bug was intermittent because depending on the typed buffer's
length the geometry sometimes aligned by accident. Drag-and-dropping
a long screencaptureui temp path into VS Code's terminal reliably
triggered it, since the path stays inline (the temp file is already
gone by paste time so collapseOrQuoteFilePaths -> pathExists
returns false -> falls through to verbatim insert).

Fix: in Editor.Render, do all wrap and cursor math against a
plain-text prompt (ANSI stripped via stripANSI), then re-attach
the styled original to the very first wrapped row's leading
substring before returning. Continuation rows already use an
indent of spaces only, so they need no styling fixup. wrapLine
itself stays ANSI-unaware on purpose: the rest of the codebase
relies on its simple rune-based behaviour for plain text and
making it ANSI-aware would be a much bigger change with regression
risk elsewhere.

Adds editor_ansi_prompt_test.go which reproduces the exact captured
live scenario (the ANSI-themed prompt + the verbatim screencaptureui
path + ' hello' typed afterwards) and asserts the cursor lands at
the visible end of the last wrapped row.

commit: 797041288d2b7c4178e2615b874552e78aa83df1
author: patriceckhart · 5mo ago · 2026-05-13 09:13 UTC
parent: 8b4b62f
signature: unsigned
refs: tag: v0.1.79

2 files · +64 -2

M internal/tui/editor.go +20 -2


@@ -741,13 +741,24 @@ func isWordSep(r rune) bool {
741	741		// visualRow/visualCol describe where the cursor lands within the returned lines.
742	742		func (e *Editor) Render(width int) (lines []string, visualRow, visualCol int) {
743	743		e.lastRenderWidth = width
744		-	promptLen := visibleWidth(e.Prompt)
	744	+	// The Prompt may carry ANSI styling (theme-coloured glyph + reset).
	745	+	// We must compute wrap geometry using its visible width only;
	746	+	// otherwise the raw escape bytes leak into wrapLine's per-rune
	747	+	// width accounting and the cursor column lands inside the row
	748	+	// instead of at the end. See the wrapLine docs for why we keep it
	749	+	// ANSI-unaware: the rest of the codebase relies on its simple
	750	+	// rune-based behaviour for plain text and would regress if we
	751	+	// taught it about escape sequences here. Strip ANSI from the
	752	+	// prompt used for layout, then re-apply the original styling to
	753	+	// the very first wrapped row before returning.
	754	+	plainPrompt := stripANSI(e.Prompt)
	755	+	promptLen := runewidth.StringWidth(plainPrompt)
745	756		indent := strings.Repeat(" ", promptLen)
746	757
747	758		for r, line := range e.Lines {
748	759		var prefix string
749	760		if r == 0 {
750		-	prefix = e.Prompt
	761	+	prefix = plainPrompt
751	762		} else {
752	763		prefix = indent
753	764		}

@@ -764,6 +775,13 @@ func (e *Editor) Render(width int) (lines []string, visualRow, visualCol int) {
764	775		visualRow = len(lines) + row
765	776		visualCol = col
766	777		}
	778	+	// Re-attach the styled prompt to the very first wrapped row of
	779	+	// the first logical line. All later rows are indent-only and
	780	+	// don't need styling. The replacement is byte-exact because the
	781	+	// plain prompt sits at the row's start.
	782	+	if r == 0 && len(wrapped) > 0 && strings.HasPrefix(wrapped[0], plainPrompt) {
	783	+	wrapped[0] = e.Prompt + wrapped[0][len(plainPrompt):]
	784	+	}
767	785		lines = append(lines, wrapped...)
768	786		}
769	787		return lines, visualRow, visualCol

 // visualRow/visualCol describe where the cursor lands within the returned lines.
 func (e *Editor) Render(width int) (lines []string, visualRow, visualCol int) {
 	e.lastRenderWidth = width
-	promptLen := visibleWidth(e.Prompt)
+	// The Prompt may carry ANSI styling (theme-coloured glyph + reset).
+	// We must compute wrap geometry using its *visible* width only;
+	// otherwise the raw escape bytes leak into wrapLine's per-rune
+	// width accounting and the cursor column lands inside the row
+	// instead of at the end. See the wrapLine docs for why we keep it
+	// ANSI-unaware: the rest of the codebase relies on its simple
+	// rune-based behaviour for plain text and would regress if we
+	// taught it about escape sequences here. Strip ANSI from the
+	// prompt used for layout, then re-apply the original styling to
+	// the very first wrapped row before returning.
+	plainPrompt := stripANSI(e.Prompt)
+	promptLen := runewidth.StringWidth(plainPrompt)
 	indent := strings.Repeat(" ", promptLen)
 	for r, line := range e.Lines {
 		var prefix string
 		if r == 0 {
-			prefix = e.Prompt
+			prefix = plainPrompt
 		} else {
 			prefix = indent
 		}
 			visualRow = len(lines) + row
 			visualCol = col
 		}
+		// Re-attach the styled prompt to the very first wrapped row of
+		// the first logical line. All later rows are indent-only and
+		// don't need styling. The replacement is byte-exact because the
+		// plain prompt sits at the row's start.
+		if r == 0 && len(wrapped) > 0 && strings.HasPrefix(wrapped[0], plainPrompt) {
+			wrapped[0] = e.Prompt + wrapped[0][len(plainPrompt):]
+		}
 		lines = append(lines, wrapped...)
 	}
 	return lines, visualRow, visualCol

A internal/tui/editor_ansi_prompt_test.go +44 -0

@@ -0,0 +1,44 @@
	1	+	package tui
	2	+
	3	+	import (
	4	+	"strings"
	5	+	"testing"
	6	+
	7	+	"github.com/mattn/go-runewidth"
	8	+	)
	9	+
	10	+	// TestEditor_AnsiPromptCursorAtEnd reproduces the live VS-Code drag
	11	+	// and drop bug: when the editor's Prompt carries ANSI styling (the
	12	+	// themed "▌ " glyph used by the interactive mode), the raw escape
	13	+	// bytes leaked into wrapLine's per-rune width counter, and the
	14	+	// cursor reported by Render() landed inside the wrapped row instead
	15	+	// of at the end. Render() must return a column equal to the visible
	16	+	// width of the last wrapped row when CursorC sits at end-of-buffer.
	17	+	func TestEditor_AnsiPromptCursorAtEnd(t *testing.T) {
	18	+	// "\x1b[38;5;111m▌ \x1b[0m" is the exact prompt the interactive
	19	+	// mode constructs via cfg.Theme.AccentBar. We hard-code the
	20	+	// bytes here so the test doesn't depend on theme internals.
	21	+	ansiPrompt := "\x1b[38;5;111m▌ \x1b[0m"
	22	+
	23	+	e := NewEditor(ansiPrompt)
	24	+	// Same scenario as the captured live session: a screencaptureui
	25	+	// temp path then " hello" typed afterwards.
	26	+	pasted := "'/var/folders/xq/hdh5qm6j66nbzd0sh3ljsxyc0000gn/T/TemporaryItems/NSIRD_screencaptureui_P22eIV/Screenshot 2026-05-13 at 11.09.28.png'"
	27	+	e.insert(pasted)
	28	+	for _, r := range " hello" {
	29	+	e.insert(string(r))
	30	+	}
	31	+
	32	+	lines, row, col := e.Render(113)
	33	+	if len(lines) == 0 {
	34	+	t.Fatalf("Render returned no lines")
	35	+	}
	36	+	last := lines[len(lines)-1]
	37	+	wantRow := len(lines) - 1
	38	+	wantCol := runewidth.StringWidth(stripANSI(last))
	39	+
	40	+	if row != wantRow \|\| col != wantCol {
	41	+	t.Fatalf("cursor at row=%d col=%d, want row=%d col=%d\nrendered rows:\n%s",
	42	+	row, col, wantRow, wantCol, strings.Join(lines, "\n"))
	43	+	}
	44	+	}

@@ -0,0 +1,44 @@
	1	+	package tui
	2	+
	3	+	import (
	4	+	"strings"
	5	+	"testing"
	6	+
	7	+	"github.com/mattn/go-runewidth"
	8	+	)
	9	+
	10	+	// TestEditor_AnsiPromptCursorAtEnd reproduces the live VS-Code drag
	11	+	// and drop bug: when the editor's Prompt carries ANSI styling (the
	12	+	// themed "▌ " glyph used by the interactive mode), the raw escape
	13	+	// bytes leaked into wrapLine's per-rune width counter, and the
	14	+	// cursor reported by Render() landed inside the wrapped row instead
	15	+	// of at the end. Render() must return a column equal to the visible
	16	+	// width of the last wrapped row when CursorC sits at end-of-buffer.
	17	+	func TestEditor_AnsiPromptCursorAtEnd(t *testing.T) {
	18	+	// "\x1b[38;5;111m▌ \x1b[0m" is the exact prompt the interactive
	19	+	// mode constructs via cfg.Theme.AccentBar. We hard-code the
	20	+	// bytes here so the test doesn't depend on theme internals.
	21	+	ansiPrompt := "\x1b[38;5;111m▌ \x1b[0m"
	22	+
	23	+	e := NewEditor(ansiPrompt)
	24	+	// Same scenario as the captured live session: a screencaptureui
	25	+	// temp path then " hello" typed afterwards.
	26	+	pasted := "'/var/folders/xq/hdh5qm6j66nbzd0sh3ljsxyc0000gn/T/TemporaryItems/NSIRD_screencaptureui_P22eIV/Screenshot 2026-05-13 at 11.09.28.png'"
	27	+	e.insert(pasted)
	28	+	for _, r := range " hello" {
	29	+	e.insert(string(r))
	30	+	}
	31	+
	32	+	lines, row, col := e.Render(113)
	33	+	if len(lines) == 0 {
	34	+	t.Fatalf("Render returned no lines")
	35	+	}
	36	+	last := lines[len(lines)-1]
	37	+	wantRow := len(lines) - 1
	38	+	wantCol := runewidth.StringWidth(stripANSI(last))
	39	+
	40	+	if row != wantRow \|\| col != wantCol {
	41	+	t.Fatalf("cursor at row=%d col=%d, want row=%d col=%d\nrendered rows:\n%s",
	42	+	row, col, wantRow, wantCol, strings.Join(lines, "\n"))
	43	+	}
	44	+	}