Avoid blank line at end of view

view.go

@@ -66,6 +66,11 @@ type View struct {
 	// true and viewLines to nil
 	viewLines []viewLine
 
+	// If the last character written was a newline, we don't write it but
+	// instead set pendingNewline to true. If more text is written, we write the
+	// newline then. This is to avoid having an extra blank at the end of the view.
+	pendingNewline bool
+
 	// writeMutex protects locks the write process
 	writeMutex sync.Mutex
 
@@ -647,6 +652,9 @@ func (v *View) SetWritePos(x, y int) {
 
 	v.wx = x
 	v.wy = y
+
+	// Changing the write position makes a pending newline obsolete
+	v.pendingNewline = false
 }
 
 // WritePos returns the current write position of the view's internal buffer.
@@ -765,15 +773,30 @@ func (v *View) writeRunes(p []rune) {
 		}
 	}
 
-	for _, r := range p {
+	advanceToNextLine := func() {
+		v.wx = 0
+		v.wy++
+		if v.wy >= len(v.lines) {
+			v.lines = append(v.lines, nil)
+		}
+	}
+
+	if v.pendingNewline {
+		advanceToNextLine()
+		v.pendingNewline = false
+	}
+
+	until := len(p)
+	if until > 0 && p[until-1] == '\n' {
+		v.pendingNewline = true
+		until--
+	}
+
+	for _, r := range p[:until] {
 		switch r {
 		case '\n':
 			finishLine()
-			v.wx = 0
-			v.wy++
-			if v.wy >= len(v.lines) {
-				v.lines = append(v.lines, nil)
-			}
+			advanceToNextLine()
 		case '\r':
 			finishLine()
 			v.wx = 0
@@ -792,6 +815,10 @@ func (v *View) writeRunes(p []rune) {
 		}
 	}
 
+	if v.pendingNewline {
+		finishLine()
+	}
+
 	v.updateSearchPositions()
 }
 

view_test.go

@@ -12,63 +12,68 @@ import (
 
 func TestWriteRunes(t *testing.T) {
 	tests := []struct {
-		existingLines []string
-		stringToWrite string
-		expectedLines []string
+		existingLines  []string
+		stringsToWrite []string
+		expectedLines  []string
 	}{
 		{
 			[]string{},
-			"",
 			[]string{""},
+			[]string{""},
+		},
+		{
+			[]string{},
+			[]string{"1\n"},
+			[]string{"1\x00"},
 		},
 		{
 			[]string{},
-			"1\n",
-			[]string{"1\x00", ""},
+			[]string{"1\n", "2\n"},
+			[]string{"1\x00", "2\x00"},
 		},
 		{
 			[]string{"a"},
-			"1\n",
-			[]string{"1\x00", ""},
+			[]string{"1\n"},
+			[]string{"1\x00"},
 		},
 		{
 			[]string{"a\x00"},
-			"1\n",
-			[]string{"1\x00", ""},
+			[]string{"1\n"},
+			[]string{"1\x00"},
 		},
 		{
 			[]string{"ab"},
-			"1\n",
-			[]string{"1b", ""},
+			[]string{"1\n"},
+			[]string{"1b"},
 		},
 		{
 			[]string{"abc"},
-			"1\n",
-			[]string{"1bc", ""},
+			[]string{"1\n"},
+			[]string{"1bc"},
 		},
 		{
 			[]string{},
-			"1\r",
+			[]string{"1\r"},
 			[]string{"1\x00"},
 		},
 		{
 			[]string{"a"},
-			"1\r",
+			[]string{"1\r"},
 			[]string{"1\x00"},
 		},
 		{
 			[]string{"a\x00"},
-			"1\r",
+			[]string{"1\r"},
 			[]string{"1\x00"},
 		},
 		{
 			[]string{"ab"},
-			"1\r",
+			[]string{"1\r"},
 			[]string{"1b"},
 		},
 		{
 			[]string{"abc"},
-			"1\r",
+			[]string{"1\r"},
 			[]string{"1bc"},
 		},
 	}
@@ -78,7 +83,9 @@ func TestWriteRunes(t *testing.T) {
 		for _, l := range test.existingLines {
 			v.lines = append(v.lines, stringToCells(l))
 		}
-		v.writeRunes([]rune(test.stringToWrite))
+		for _, s := range test.stringsToWrite {
+			v.writeRunes([]rune(s))
+		}
 		var resultingLines []string
 		for _, l := range v.lines {
 			resultingLines = append(resultingLines, cellsToString(l))