Merge branch 'setmaxlines' into 'master'

TextView: Add SetMaxLines()

See merge request tslocum/cview!3

textview.go

@@ -136,6 +136,9 @@ type TextView struct {
 	// The index of the first line shown in the text view.
 	lineOffset int
 
+	// The maximum number of liens the text view will hold (set to 0 for no limit)
+	maxLines int
+
 	// If set to true, the text view will always remain at the end of the content.
 	trackEnd bool
 
@@ -203,6 +206,7 @@ func NewTextView() *TextView {
 		textColor:     Styles.PrimaryTextColor,
 		regions:       false,
 		dynamicColors: false,
+		maxLines:      0,
 	}
 }
 
@@ -389,6 +393,23 @@ func (t *TextView) SetHighlightedFunc(handler func(added, removed, remaining []s
 	return t
 }
 
+func (t *TextView) clipBuffer() {
+	if t.maxLines > 0 {
+		lenbuf := len(t.buffer)
+		if lenbuf > t.maxLines {
+			t.buffer = t.buffer[lenbuf-t.maxLines:]
+		}
+	}
+}
+
+// SetMaxLines establishes the maximum amount of lines the text view will hold
+// before discarding older data from the buffer
+func (t *TextView) SetMaxLines(maxLines int) *TextView {
+	t.maxLines = maxLines
+	t.clipBuffer()
+	return t
+}
+
 // ScrollTo scrolls to the specified row and column (both starting with 0).
 func (t *TextView) ScrollTo(row, column int) *TextView {
 	t.Lock()
@@ -722,6 +743,8 @@ func (t *TextView) write(p []byte) (n int, err error) {
 		}
 	}
 
+	t.clipBuffer()
+
 	// Reset the index.
 	t.index = nil
 

textview_test.go

@@ -3,6 +3,7 @@ package cview
 import (
 	"bytes"
 	"fmt"
+	"strings"
 	"testing"
 )
 
@@ -195,6 +196,48 @@ func BenchmarkTextViewDraw(b *testing.B) {
 	}
 }
 
+func TestTextViewMaxLines(t *testing.T) {
+	tv := NewTextView()
+
+	// append 100 lines with no limit set:
+	for i := 0; i < 100; i++ {
+		tv.Write([]byte(fmt.Sprintf("L%d\n", i)))
+	}
+
+	// retrieve the total text and see we have the 100 lines:
+	count := strings.Count(tv.GetText(true), "\n")
+	if count != 100 {
+		t.Fatalf("Expected 100 lines, got %d", count)
+	}
+
+	// now set the maximum lines to 20, this should clip the buffer:
+	tv.SetMaxLines(20)
+	// verify buffer was clipped:
+	count = len(strings.Split(tv.GetText(true), "\n"))
+	if count != 20 {
+		t.Fatalf("Expected 20 lines, got %d", count)
+	}
+
+	// append 100 more lines:
+	for i := 100; i < 200; i++ {
+		tv.Write([]byte(fmt.Sprintf("L%d\n", i)))
+	}
+
+	// Sice max lines is set to 20, we should still get 20 lines:
+	txt := tv.GetText(true)
+	lines := strings.Split(txt, "\n")
+	count = len(lines)
+	if count != 20 {
+		t.Fatalf("Expected 20 lines, got %d", count)
+	}
+
+	// and those 20 lines should be the last ones:
+	if lines[0] != "L181" {
+		t.Fatalf("Expected to get L181, got %s", lines[0])
+	}
+
+}
+
 func generateTestCases() []*textViewTestCase {
 	var cases []*textViewTestCase
 	for i := 0; i < 2; i++ {