fix: incorrect line skipping in renderer flush (#1233)

* fix line skip in flush * mod tidy in examples dir * reset lastRenderedLines on repaint * docs: add note * fix: simplify line skip logic --------- Co-authored-by: Ayman Bagabas <ayman.bagabas@gmail.com>
charmbracelet · Nov 12, 2024 · 97fc4fa · 97fc4fa
1 parent 1feb60b
commit 97fc4fa
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Showing 3 changed files with 19 additions and 14 deletions.
diff --git a/examples/go.mod b/examples/go.mod
@@ -24,7 +24,7 @@ require (
 	github.com/aymerick/douceur v0.2.0 // indirect
 	github.com/charmbracelet/x/ansi v0.4.5 // indirect
 	github.com/charmbracelet/x/exp/golden v0.0.0-20240815200342-61de596daa2b // indirect
-	github.com/charmbracelet/x/term v0.2.0 // indirect
+	github.com/charmbracelet/x/term v0.2.1 // indirect
 	github.com/dlclark/regexp2 v1.11.0 // indirect
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f // indirect
@@ -41,8 +41,8 @@ require (
 	github.com/yuin/goldmark v1.7.4 // indirect
 	github.com/yuin/goldmark-emoji v1.0.3 // indirect
 	golang.org/x/net v0.27.0 // indirect
-	golang.org/x/sync v0.8.0 // indirect
-	golang.org/x/sys v0.26.0 // indirect
+	golang.org/x/sync v0.9.0 // indirect
+	golang.org/x/sys v0.27.0 // indirect
 	golang.org/x/term v0.22.0 // indirect
 	golang.org/x/text v0.19.0 // indirect
 )

diff --git a/examples/go.sum b/examples/go.sum
@@ -28,8 +28,8 @@ github.com/charmbracelet/x/exp/golden v0.0.0-20240815200342-61de596daa2b h1:MnAM
 github.com/charmbracelet/x/exp/golden v0.0.0-20240815200342-61de596daa2b/go.mod h1:wDlXFlCrmJ8J+swcL/MnGUuYnqgQdW9rhSD61oNMb6U=
 github.com/charmbracelet/x/exp/teatest v0.0.0-20240521184646-23081fb03b28 h1:sOWKNRjt8uOEVgPiJVIJCse1+mUDM2F/vYY6W0Go640=
 github.com/charmbracelet/x/exp/teatest v0.0.0-20240521184646-23081fb03b28/go.mod h1:l1w+LTJZCCozeGzMEWGxRw6Mo2DfcZUvupz8HGubdes=
-github.com/charmbracelet/x/term v0.2.0 h1:cNB9Ot9q8I711MyZ7myUR5HFWL/lc3OpU8jZ4hwm0x0=
-github.com/charmbracelet/x/term v0.2.0/go.mod h1:GVxgxAbjUrmpvIINHIQnJJKpMlHiZ4cktEQCN6GWyF0=
+github.com/charmbracelet/x/term v0.2.1 h1:AQeHeLZ1OqSXhrAWpYUtZyX1T3zVxfpZuEQMIQaGIAQ=
+github.com/charmbracelet/x/term v0.2.1/go.mod h1:oQ4enTYFV7QN4m0i9mzHrViD7TQKvNEEkHUMCmsxdUg=
 github.com/dlclark/regexp2 v1.11.0 h1:G/nrcoOa7ZXlpoa/91N3X7mM3r8eIlMBBJZvsz/mxKI=
 github.com/dlclark/regexp2 v1.11.0/go.mod h1:DHkYz0B9wPfa6wondMfaivmHpzrQ3v9q8cnmRbL6yW8=
 github.com/dustin/go-humanize v1.0.1 h1:GzkhY7T5VNhEkwH0PVJgjz+fX1rhBrR7pRT3mDkpeCY=
@@ -76,12 +76,12 @@ github.com/yuin/goldmark-emoji v1.0.3 h1:aLRkLHOuBR2czCY4R8olwMjID+tENfhyFDMCRhb
 github.com/yuin/goldmark-emoji v1.0.3/go.mod h1:tTkZEbwu5wkPmgTcitqddVxY9osFZiavD+r4AzQrh1U=
 golang.org/x/net v0.27.0 h1:5K3Njcw06/l2y9vpGCSdcxWOYHOUk3dVNGDXN+FvAys=
 golang.org/x/net v0.27.0/go.mod h1:dDi0PyhWNoiUOrAS8uXv/vnScO4wnHQO4mj9fn/RytE=
-golang.org/x/sync v0.8.0 h1:3NFvSEYkUoMifnESzZl15y791HH1qU2xm6eCJU5ZPXQ=
-golang.org/x/sync v0.8.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
+golang.org/x/sync v0.9.0 h1:fEo0HyrW1GIgZdpbhCRO0PkJajUS5H9IFUztCgEo2jQ=
+golang.org/x/sync v0.9.0/go.mod h1:Czt+wKu1gCyEFDUtn0jG5QVvpJ6rzVqr5aXyt9drQfk=
 golang.org/x/sys v0.0.0-20210809222454-d867a43fc93e/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.26.0 h1:KHjCJyddX0LoSTb3J+vWpupP9p0oznkqVk/IfjymZbo=
-golang.org/x/sys v0.26.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/sys v0.27.0 h1:wBqf8DvsY9Y/2P8gAfPDEYNuS30J4lPHJxXSb/nJZ+s=
+golang.org/x/sys v0.27.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/term v0.22.0 h1:BbsgPEJULsl2fV/AT3v15Mjva5yXKQDyKf+TbDz7QJk=
 golang.org/x/term v0.22.0/go.mod h1:F3qCibpT5AMpCRfhfT53vVJwhLtIVHhB9XDjfFvnMI4=
 golang.org/x/text v0.19.0 h1:kTxAhCbGbxhK0IwgSKiMO5awPoDQ0RpfiVYBfK860YM=

diff --git a/standard_renderer.go b/standard_renderer.go
@@ -34,6 +34,7 @@ type standardRenderer struct {
 	ticker             *time.Ticker
 	done               chan struct{}
 	lastRender         string
+	lastRenderedLines  []string
 	linesRendered      int
 	useANSICompressor  bool
 	once               sync.Once
@@ -174,7 +175,6 @@ func (r *standardRenderer) flush() {
 	}
 
 	newLines := strings.Split(r.buf.String(), "\n")
-	oldLines := strings.Split(r.lastRender, "\n")
 
 	// If we know the output's height, we can use it to determine how many
 	// lines we can render. We drop lines from the top of the render buffer if
@@ -184,7 +184,6 @@ func (r *standardRenderer) flush() {
 		newLines = newLines[len(newLines)-r.height:]
 	}
 
-	numLinesThisFlush := len(newLines)
 	flushQueuedMessages := len(r.queuedMessageLines) > 0 && !r.altScreenActive
 
 	if flushQueuedMessages {
@@ -210,7 +209,7 @@ func (r *standardRenderer) flush() {
 	// Paint new lines.
 	for i := 0; i < len(newLines); i++ {
 		canSkip := !flushQueuedMessages && // Queuing messages triggers repaint -> we don't have access to previous frame content.
-			len(oldLines) > i && oldLines[i] == newLines[i] // Previously rendered line is the same.
+			len(r.lastRenderedLines) > i && r.lastRenderedLines[i] == newLines[i] // Previously rendered line is the same.
 
 		if _, ignore := r.ignoreLines[i]; ignore || canSkip {
 			// Unless this is the last line, move the cursor down.
@@ -257,11 +256,11 @@ func (r *standardRenderer) flush() {
 	}
 
 	// Clearing left over content from last render.
-	if r.linesRendered > numLinesThisFlush {
+	if r.linesRendered > len(newLines) {
 		buf.WriteString(ansi.EraseScreenBelow)
 	}
 
-	r.linesRendered = numLinesThisFlush
+	r.linesRendered = len(newLines)
 
 	// Make sure the cursor is at the start of the last line to keep rendering
 	// behavior consistent.
@@ -276,6 +275,11 @@ func (r *standardRenderer) flush() {
 
 	_, _ = r.out.Write(buf.Bytes())
 	r.lastRender = r.buf.String()
+
+	// Save previously rendered lines for comparison in the next render. If we
+	// don't do this, we can't skip rendering lines that haven't changed.
+	// See https://github.com/charmbracelet/bubbletea/pull/1233
+	r.lastRenderedLines = newLines
 	r.buf.Reset()
 }
 
@@ -299,6 +303,7 @@ func (r *standardRenderer) write(s string) {
 
 func (r *standardRenderer) repaint() {
 	r.lastRender = ""
+	r.lastRenderedLines = nil
 }
 
 func (r *standardRenderer) clearScreen() {