matrix now only refreshes modified rows (#36)

matrix.go

@@ -56,21 +56,23 @@ type MatrixRow interface {
 }
 
 type matrixImpl struct {
-	lines           []string
+	rows            []*matrixRow
 	refreshInterval time.Duration
 	writer          io.Writer
 	mx              *sync.RWMutex
 }
 
 type matrixRow struct {
-	id     MatrixCellID
-	matrix *matrixImpl
+	id       MatrixCellID
+	matrix   *matrixImpl
+	value    string
+	modified bool
 }
 
 // NewMatrix creates a new matrix that writes to the specified writer and refreshes every refreshInterval.
 func NewMatrix(writer io.Writer, refreshInterval time.Duration) Matrix {
 	return &matrixImpl{
-		lines:           []string{},
+		rows:            []*matrixRow{},
 		refreshInterval: refreshInterval,
 		writer:          writer,
 		mx:              &sync.RWMutex{},
@@ -127,14 +129,11 @@ func (m *matrixImpl) GetRow(index int) (row MatrixRow, err error) {
 	if index < 0 {
 		return nil, errors.New("row index cannot be negative")
 	}
-	if index >= len(m.lines) {
+	if index >= len(m.rows) {
 		return nil, errors.New("row index exceeds the matrix range")
 	}
 
-	row = &matrixRow{
-		id:     MatrixCellID{row: index},
-		matrix: m,
-	}
+	row = m.rows[index]
 
 	return row, err
 }
@@ -148,16 +147,21 @@ func (m *matrixImpl) updateTerminal(resetCursorPosition bool) {
 	m.mx.Lock()
 	defer m.mx.Unlock()
 
-	if len(m.lines) == 0 {
+	if len(m.rows) == 0 {
 		return
 	}
 
-	for _, line := range m.lines {
-		io.WriteString(m.writer, fmt.Sprintf("%s%s\r\n", TermControlEraseLine, line))
+	for _, row := range m.rows {
+		if row.modified {
+			_, err := io.WriteString(m.writer, fmt.Sprintf("%s%s\n", TermControlEraseLine, row.value))
+			row.modified = err != nil
+		} else {
+			io.WriteString(m.writer, "\n")
+		}
 	}
 
 	if resetCursorPosition {
-		c.Up(len(m.lines))
+		c.Up(len(m.rows))
 	}
 }
 
@@ -189,12 +193,14 @@ func (m *matrixImpl) NewRow() MatrixRow {
 }
 
 func (m *matrixImpl) newRow() MatrixRow {
-	index := len(m.lines)
-	m.lines = append(m.lines, "")
-	return &matrixRow{
+	index := len(m.rows)
+	row := &matrixRow{
 		id:     MatrixCellID{row: index},
 		matrix: m,
 	}
+	m.rows = append(m.rows, row)
+
+	return row
 }
 
 func (r *matrixRow) WriteString(s string) (n int, err error) {
@@ -205,8 +211,11 @@ func (r *matrixRow) Write(b []byte) (n int, err error) {
 	r.matrix.mx.Lock()
 	defer r.matrix.mx.Unlock()
 
-	// we trim line feeds and return characters to prevent breaking the matrix layout
-	r.matrix.lines[r.id.row] = strings.Trim(string(b), "\n\r")
+	row := r.matrix.rows[r.id.row]
+	newValue := strings.Trim(string(b), "\n\r")
+	row.modified = newValue != row.value
+	row.value = newValue
+
 	return len(b), nil
 }
 

matrix_test.go

@@ -22,7 +22,7 @@ func TestMatrixWritesToTerminalOutput(t *testing.T) {
 	matrix.NewLineWriter().Write([]byte(examples[1]))
 	matrix.NewLineStringWriter().WriteString(examples[2])
 
-	assertEventualSequence(t, matrix, examples)
+	assertEventualSequence(t, matrix, expectedRewriteSequenceFor(examples))
 }
 
 func TestMatrixUpdatesTerminalOutput(t *testing.T) {
@@ -38,7 +38,7 @@ func TestMatrixUpdatesTerminalOutput(t *testing.T) {
 	matrix.NewRow().Update(examples[2])
 	row2.WriteString(examples[1])
 
-	assertEventualSequence(t, matrix, examples)
+	assertEventualSequence(t, matrix, expectedRewriteSequenceFor(examples))
 }
 
 func TestMatrixRowUpdateTrimsLineFeeds(t *testing.T) {
@@ -47,9 +47,18 @@ func TestMatrixRowUpdateTrimsLineFeeds(t *testing.T) {
 	matrix, cancel := startNewMatrix()
 	defer cancel()
 
-	matrix.NewRow().Update("\r\n" + expected + "\r\n\r\n\r")
+	matrix.NewRow().Update("\n" + expected + "\n\n\r")
 
-	assertEventualSequence(t, matrix, []string{expected})
+	assertEventualSequence(t, matrix, expectedRewriteSequenceFor([]string{expected}))
+}
+
+func TestNoRewritesWhenNothingChanges(t *testing.T) {
+	matrix, cancel := startNewMatrix()
+	defer cancel()
+
+	matrix.NewRange(4)
+
+	assertEventualSequence(t, matrix, expectedSkipRewriteSequenceFor(4))
 }
 
 func TestMatrixStructure(t *testing.T) {
@@ -62,7 +71,7 @@ func TestMatrixStructure(t *testing.T) {
 	matrix.NewRow().Update(examples[1])
 	matrix.NewRow().Update(examples[2])
 
-	assert.Equal(t, examples, matrix.(*matrixImpl).lines)
+	assert.Equal(t, examples, linesOf(matrix))
 }
 
 func TestMatrixNewRangeOrder(t *testing.T) {
@@ -76,7 +85,7 @@ func TestMatrixNewRangeOrder(t *testing.T) {
 		rows[i].Update(examples[i])
 	}
 
-	assert.Equal(t, examples, matrix.(*matrixImpl).lines)
+	assert.Equal(t, examples, linesOf(matrix))
 }
 
 func TestWriterLineInterface(t *testing.T) {
@@ -91,7 +100,7 @@ func TestWriterLineInterface(t *testing.T) {
 	matrix1.NewLineStringWriter().WriteString(example)
 	matrix2.NewLineWriter().Write([]byte(example))
 
-	assert.Equal(t, matrix1.(*matrixImpl).lines, matrix2.(*matrixImpl).lines)
+	assert.Equal(t, matrix1.(*matrixImpl).rows, matrix2.(*matrixImpl).rows)
 }
 
 func TestMatrixGetRowByID(t *testing.T) {
@@ -125,11 +134,11 @@ func TestMatrixGetRowByIdWithIllegalValue(t *testing.T) {
 	assert.Error(t, err)
 }
 
-func assertEventualSequence(t *testing.T, matrix Matrix, examples []string) {
+func assertEventualSequence(t *testing.T, matrix Matrix, expected string) {
 	contantsAllExamplesInOrderFn := func() bool {
 		return strings.Contains(
 			matrix.(*matrixImpl).writer.(*bytes.Buffer).String(),
-			expectedOutputSequenceFor(examples),
+			expected,
 		)
 	}
 
@@ -138,12 +147,16 @@ func assertEventualSequence(t *testing.T, matrix Matrix, examples []string) {
 		time.Second*10,
 		matrix.RefreshInterval(),
 	)
+}
 
+func expectedSkipRewriteSequenceFor(count int) string {
+	return strings.Repeat("\n", count)
 }
-func expectedOutputSequenceFor(examples []string) string {
+
+func expectedRewriteSequenceFor(examples []string) string {
 	buf := new(bytes.Buffer)
 	for _, e := range examples {
-		buf.WriteString(TermControlEraseLine + e + "\r\n")
+		buf.WriteString(TermControlEraseLine + e + "\n")
 	}
 
 	return buf.String()
@@ -170,3 +183,13 @@ func generateMultiLineExamples(count int) []string {
 
 	return examples
 }
+
+func linesOf(m Matrix) []string {
+	rows := m.(*matrixImpl).rows
+	lines := make([]string, len(rows))
+	for i, row := range rows {
+		lines[i] = row.value
+	}
+
+	return lines
+}