Preserve terminal selections during repaints

commit: 3e4884f829f203802942c6fbf8e6720052451ec6
author: patriceckhart · 3mo ago · 2026-07-13 16:55 UTC
parent: 1b17517
signature: unsigned

2 files · +57 -6

M packages/tui/render.go +15 -6


@@ -483,7 +483,7 @@ func (r *Renderer) DrawLog(chat, bottom []string, cursorBottomRow, cursorCol int
483	483		w.WriteString(SeqSynchronizedOn)
484	484		w.WriteString(SeqHideCursor)
485	485
486		-	writeFull := func(clear bool) {
	486	+	writeFull := func(clear, purgeScrollback bool) {
487	487		if clear {
488	488		w.WriteString(SeqDeleteKittyImages)
489	489		if r.keepScrollback {

@@ -500,7 +500,13 @@ func (r *Renderer) DrawLog(chat, bottom []string, cursorBottomRow, cursorCol int
500	500		w.WriteString(SeqClearToEnd)
501	501		} else {
502	502		w.WriteString(SeqClearScreenNoHome)
503		-	w.WriteString(r.clearScrollbackSeq())
	503	+	// Purging scrollback invalidates native terminal selections.
	504	+	// It is safe on the first paint because no zot output can be
	505	+	// selected yet, but implicit recovery repaints happen while an
	506	+	// agent is streaming and must preserve the user's selection.
	507	+	if purgeScrollback {
	508	+	w.WriteString(r.clearScrollbackSeq())
	509	+	}
504	510		w.WriteString(MoveTo(1, 1))
505	511		}
506	512		}

@@ -576,9 +582,10 @@ func (r *Renderer) DrawLog(chat, bottom []string, cursorBottomRow, cursorCol int
576	582		// because the cached entry was the \x00 sentinel rather than the
577	583		// real previous bg-colored row.
578	584
579		-	full := !r.logInit \|\| len(r.logLines) == 0
	585	+	wasInitialized := r.logInit
	586	+	full := !wasInitialized \|\| len(r.logLines) == 0
580	587		if full {
581		-	writeFull(true)
	588	+	writeFull(true, !wasInitialized)
582	589		r.logInit = true
583	590		} else {
584	591		firstChanged := -1

@@ -623,7 +630,9 @@ func (r *Renderer) DrawLog(chat, bottom []string, cursorBottomRow, cursorCol int
623	630		// move the hardware cursor if the editor cursor changed.
624	631		} else if firstChanged < r.logViewportTop {
625	632		// Changes above the visible viewport cannot be patched safely.
626		-	writeFull(true)
	633	+	// Repaint without erasing scrollback: the terminal may have a
	634	+	// native text selection anchored there while output streams.
	635	+	writeFull(true, false)
627	636		} else {
628	637		prevViewportTop := r.logViewportTop
629	638		viewportTop := prevViewportTop

@@ -686,7 +695,7 @@ func (r *Renderer) DrawLog(chat, bottom []string, cursorBottomRow, cursorCol int
686	695		if len(r.logLines) > len(lines) {
687	696		extra := len(r.logLines) - len(lines)
688	697		if extra > r.rows {
689		-	writeFull(true)
	698	+	writeFull(true, false)
690	699		} else {
691	700		for e := 0; e < extra; e++ {
692	701		w.WriteString("\x1b[1B")

 	w.WriteString(SeqSynchronizedOn)
 	w.WriteString(SeqHideCursor)
-	writeFull := func(clear bool) {
+	writeFull := func(clear, purgeScrollback bool) {
 		if clear {
 			w.WriteString(SeqDeleteKittyImages)
 			if r.keepScrollback {
 				w.WriteString(SeqClearToEnd)
 			} else {
 				w.WriteString(SeqClearScreenNoHome)
-				w.WriteString(r.clearScrollbackSeq())
+				// Purging scrollback invalidates native terminal selections.
+				// It is safe on the first paint because no zot output can be
+				// selected yet, but implicit recovery repaints happen while an
+				// agent is streaming and must preserve the user's selection.
+				if purgeScrollback {
+					w.WriteString(r.clearScrollbackSeq())
+				}
 				w.WriteString(MoveTo(1, 1))
 			}
 		}
 	// because the cached entry was the \x00 sentinel rather than the
 	// real previous bg-colored row.
-	full := !r.logInit || len(r.logLines) == 0
+	wasInitialized := r.logInit
+	full := !wasInitialized || len(r.logLines) == 0
 	if full {
-		writeFull(true)
+		writeFull(true, !wasInitialized)
 		r.logInit = true
 	} else {
 		firstChanged := -1
 			// move the hardware cursor if the editor cursor changed.
 		} else if firstChanged < r.logViewportTop {
 			// Changes above the visible viewport cannot be patched safely.
-			writeFull(true)
+			// Repaint without erasing scrollback: the terminal may have a
+			// native text selection anchored there while output streams.
+			writeFull(true, false)
 		} else {
 			prevViewportTop := r.logViewportTop
 			viewportTop := prevViewportTop
 			if len(r.logLines) > len(lines) {
 				extra := len(r.logLines) - len(lines)
 				if extra > r.rows {
-					writeFull(true)
+					writeFull(true, false)
 				} else {
 					for e := 0; e < extra; e++ {
 						w.WriteString("\x1b[1B")

M packages/tui/render_test.go +42 -0


@@ -101,3 +101,45 @@ func TestDrawLogResizeForcesFullRedraw(t *testing.T) {
101	101		t.Fatal("post-resize redraw skipped; the new frame would never reach the terminal")
102	102		}
103	103		}
	104	+
	105	+	// TestDrawLogRecoveryPreservesScrollbackSelection covers long streaming
	106	+	// output whose changing first row has already scrolled above the viewport.
	107	+	// DrawLog must repaint in that case, but erasing terminal scrollback also
	108	+	// erases the text backing any native mouse selection the user is making.
	109	+	func TestDrawLogRecoveryPreservesScrollbackSelection(t *testing.T) {
	110	+	t.Setenv("TERM_PROGRAM", "")
	111	+	var buf bytes.Buffer
	112	+	r := NewRenderer(&buf)
	113	+	r.Resize(80, 3)
	114	+	r.DrawLog([]string{"partial", "line 2", "line 3", "line 4"}, []string{"input"}, 0, 0)
	115	+	buf.Reset()
	116	+
	117	+	// The changed row is above logViewportTop, forcing the recovery repaint
	118	+	// used while a long streamed response continues to be reformatted.
	119	+	r.DrawLog([]string{"partial response", "line 2", "line 3", "line 4"}, []string{"input"}, 0, 0)
	120	+	got := buf.String()
	121	+	if !strings.Contains(got, SeqClearScreenNoHome) {
	122	+	t.Fatalf("recovery path did not repaint the screen: %q", got)
	123	+	}
	124	+	if strings.Contains(got, SeqClearScrollback) {
	125	+	t.Fatalf("recovery repaint erased scrollback and native selection: %q", got)
	126	+	}
	127	+	}
	128	+
	129	+	// TestDrawLogInvalidationPreservesScrollbackSelection pins the same rule for
	130	+	// cache invalidations, which can happen during an active turn independently
	131	+	// of an inaccessible changed row.
	132	+	func TestDrawLogInvalidationPreservesScrollbackSelection(t *testing.T) {
	133	+	t.Setenv("TERM_PROGRAM", "")
	134	+	var buf bytes.Buffer
	135	+	r := NewRenderer(&buf)
	136	+	r.Resize(80, 3)
	137	+	r.DrawLog([]string{"one", "two", "three", "four"}, []string{"input"}, 0, 0)
	138	+	buf.Reset()
	139	+
	140	+	r.Invalidate()
	141	+	r.DrawLog([]string{"one", "two", "three", "four"}, []string{"input"}, 0, 0)
	142	+	if got := buf.String(); strings.Contains(got, SeqClearScrollback) {
	143	+	t.Fatalf("invalidation repaint erased scrollback and native selection: %q", got)
	144	+	}
	145	+	}


@@ -101,3 +101,45 @@ func TestDrawLogResizeForcesFullRedraw(t *testing.T) {
101	t.Fatal("post-resize redraw skipped; the new frame would never reach the terminal")	101		t.Fatal("post-resize redraw skipped; the new frame would never reach the terminal")
102	}	102		}
103	}	103		}
		104	+
		105	+	// TestDrawLogRecoveryPreservesScrollbackSelection covers long streaming
		106	+	// output whose changing first row has already scrolled above the viewport.
		107	+	// DrawLog must repaint in that case, but erasing terminal scrollback also
		108	+	// erases the text backing any native mouse selection the user is making.
		109	+	func TestDrawLogRecoveryPreservesScrollbackSelection(t *testing.T) {
		110	+	t.Setenv("TERM_PROGRAM", "")
		111	+	var buf bytes.Buffer
		112	+	r := NewRenderer(&buf)
		113	+	r.Resize(80, 3)
		114	+	r.DrawLog([]string{"partial", "line 2", "line 3", "line 4"}, []string{"input"}, 0, 0)
		115	+	buf.Reset()
		116	+
		117	+	// The changed row is above logViewportTop, forcing the recovery repaint
		118	+	// used while a long streamed response continues to be reformatted.
		119	+	r.DrawLog([]string{"partial response", "line 2", "line 3", "line 4"}, []string{"input"}, 0, 0)
		120	+	got := buf.String()
		121	+	if !strings.Contains(got, SeqClearScreenNoHome) {
		122	+	t.Fatalf("recovery path did not repaint the screen: %q", got)
		123	+	}
		124	+	if strings.Contains(got, SeqClearScrollback) {
		125	+	t.Fatalf("recovery repaint erased scrollback and native selection: %q", got)
		126	+	}
		127	+	}
		128	+
		129	+	// TestDrawLogInvalidationPreservesScrollbackSelection pins the same rule for
		130	+	// cache invalidations, which can happen during an active turn independently
		131	+	// of an inaccessible changed row.
		132	+	func TestDrawLogInvalidationPreservesScrollbackSelection(t *testing.T) {
		133	+	t.Setenv("TERM_PROGRAM", "")
		134	+	var buf bytes.Buffer
		135	+	r := NewRenderer(&buf)
		136	+	r.Resize(80, 3)
		137	+	r.DrawLog([]string{"one", "two", "three", "four"}, []string{"input"}, 0, 0)
		138	+	buf.Reset()
		139	+
		140	+	r.Invalidate()
		141	+	r.DrawLog([]string{"one", "two", "three", "four"}, []string{"input"}, 0, 0)
		142	+	if got := buf.String(); strings.Contains(got, SeqClearScrollback) {
		143	+	t.Fatalf("invalidation repaint erased scrollback and native selection: %q", got)
		144	+	}
		145	+	}