Separate redraws from view-line invalidation

A view can need repainting even when its cached wrapping is still valid.
Track that state independently so content-only flushes do not overload
tainted, whose only job is to request a viewLines rebuild.

pkg/gocui/gui.go

@@ -1598,10 +1598,10 @@ func (g *Gui) flush() error {
 	return nil
 }
 
-// Redraws only tainted views and skips the layout pass.
+// Redraws only dirty views and skips the layout pass.
 // tcell's cell-level dirty tracking ensures only
 // actually-changed cells are emitted to the terminal.
-// Will also redraw any views that overlap tainted views
+// Will also redraw any views that overlap dirty views.
 func (g *Gui) flushContentOnly(views []*View) {
 	// The screen must not be touched while suspended (see Suspend).
 	if g.isSuspended() {
@@ -1619,7 +1619,7 @@ func viewsToRedrawContentOnly(views []*View) []*View {
 	redrawIndexes := set.New[int]()
 
 	for i, v := range views {
-		if !v.IsTainted() && !redrawIndexes.Includes(i) {
+		if !v.NeedsRedraw() && !redrawIndexes.Includes(i) {
 			continue
 		}
 
@@ -1649,7 +1649,7 @@ func (g *Gui) ForceLayoutAndRedraw() error {
 	return g.flush()
 }
 
-// Redraws only tainted views outside of the normal main
+// Redraws only dirty views outside of the normal main
 // loop, without a layout pass. Useful during longer operations that block the
 // main thread, e.g. to update a spinner in a status view.
 func (g *Gui) ForceFlushViewsContentOnly(views []*View) {

pkg/gocui/view.go

@@ -86,6 +86,11 @@ type View struct {
 	// tained is true if the viewLines must be updated
 	tainted bool
 
+	// needsRedraw is true if the view's current state has not been drawn to the
+	// screen yet. A tainted view always needs a redraw, but draw-only state can
+	// require one without invalidating viewLines.
+	needsRedraw bool
+
 	// firstDirtyLine is the index of the lowest line in `lines` that has been
 	// written to since viewLines was last refreshed, and whose cached wrapping
 	// (lineType.wrappedCells) may therefore be stale. Lines below it are
@@ -274,11 +279,18 @@ type pos struct {
 // a view whose size has changed, whose content is the same but has to be wrapped
 // afresh, call RewrapContent instead.
 func (v *View) clearViewLines() {
-	v.tainted = true
+	v.markViewLinesDirty()
 	v.viewLines = nil
 	v.clearHover()
 }
 
+// markViewLinesDirty records that the cached viewLines no longer represent the
+// view's buffer or wrapping, so both rebuilding and redrawing are required.
+func (v *View) markViewLinesDirty() {
+	v.tainted = true
+	v.needsRedraw = true
+}
+
 // RewrapContent wraps the view's content for the size the view has now, and puts
 // the positions into that content — the scroll offset, the cursor, a range's
 // anchor — back on the lines they were on. They are all view lines, which count
@@ -793,6 +805,7 @@ func NewView(name string, x0, y0, x1, y1 int, mode OutputMode) *View {
 		Frame:             true,
 		Editor:            DefaultEditor,
 		tainted:           true,
+		needsRedraw:       true,
 		outMode:           mode,
 		buf:               &viewBuffer{ei: newEscapeInterpreter(mode)},
 		searcher:          &searcher{},
@@ -1177,7 +1190,7 @@ func (v *View) write(p []byte) {
 		return
 	}
 
-	v.tainted = true
+	v.markViewLinesDirty()
 	// write only ever touches lines from v.buf.wy onwards, so any cached wrapping
 	// below that stays valid.
 	v.firstDirtyLine = min(v.firstDirtyLine, v.buf.wy)
@@ -1612,7 +1625,7 @@ func (v *View) SwapInOffscreenRender() {
 	}
 	v.buf = v.offscreen
 	v.offscreen = nil
-	v.tainted = true
+	v.markViewLinesDirty()
 	v.clearHover()
 }
 
@@ -1776,6 +1789,12 @@ func (v *View) IsTainted() bool {
 	return v.tainted
 }
 
+func (v *View) NeedsRedraw() bool {
+	v.writeMutex.Lock()
+	defer v.writeMutex.Unlock()
+	return v.needsRedraw
+}
+
 // draw re-draws the view's contents.
 func (v *View) draw(isWindowFocused bool) {
 	v.writeMutex.Lock()
@@ -1784,6 +1803,7 @@ func (v *View) draw(isWindowFocused bool) {
 	if !v.Visible {
 		return
 	}
+	defer func() { v.needsRedraw = false }()
 
 	v.clearRunes()