From b1e9196e14a24464d6c6ea9c5ccd5f999612f8c5 Mon Sep 17 00:00:00 2001
From: Paris Kasidiaris <paris@sourcelair.com>
Date: Wed, 14 Dec 2016 13:33:35 +0200
Subject: [PATCH 1/3] Implement baseline for `Lines` class

---
 src/Lines.ts | 38 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 src/Lines.ts

diff --git a/src/Lines.ts b/src/Lines.ts
new file mode 100644
index 0000000000..9312a58ee8
--- /dev/null
+++ b/src/Lines.ts
@@ -0,0 +1,38 @@
+/**
+ * @license MIT
+ */
+
+type Char = [number, string, number];
+type Line = Char[];  // Array of characters in tuple format
+
+export class Lines {
+  private data: Line[];  // Array of lines
+
+  constructor(data: Line[] = []) {
+    this.data = data;
+  }
+
+  get length() {
+    return this.data.length;
+  }
+
+  get(index: number) {
+    return this.data[index];
+  }
+
+  set(index: number, value: Line) {
+    return this.data[index] = value;
+  }
+
+  push(line: Line) {
+    return this.data.push(line);
+  }
+
+  slice(begin: number, end?: number) {
+    return this.data.slice(begin, end);
+  }
+
+  splice(start: number, deleteCount: number, ...items: Line[]) {
+    return this.data.splice.apply(this.data, [start, deleteCount, ...items]);
+  }
+}

From 6c1601eb0b95819d68ecc5f399e533021c9f0863 Mon Sep 17 00:00:00 2001
From: Paris Kasidiaris <paris@sourcelair.com>
Date: Wed, 14 Dec 2016 13:51:54 +0200
Subject: [PATCH 2/3] Replace line array with `Lines` class in `src/xterm.js`

---
 src/Lines.ts |  4 +++
 src/xterm.js | 82 ++++++++++++++++++++++++++--------------------------
 2 files changed, 45 insertions(+), 41 deletions(-)

diff --git a/src/Lines.ts b/src/Lines.ts
index 9312a58ee8..9e5c7926f1 100644
--- a/src/Lines.ts
+++ b/src/Lines.ts
@@ -24,6 +24,10 @@ export class Lines {
     return this.data[index] = value;
   }
 
+  pop() {
+    return this.data.pop();
+  }
+
   push(line: Line) {
     return this.data.push(line);
   }
diff --git a/src/xterm.js b/src/xterm.js
index 12c236f048..3e88ec51ea 100644
--- a/src/xterm.js
+++ b/src/xterm.js
@@ -12,6 +12,7 @@
 
 import { CompositionHelper } from './CompositionHelper.js';
 import { EventEmitter } from './EventEmitter.js';
+import { Lines } from './Lines';
 import { Viewport } from './Viewport.js';
 import { rightClickHandler, pasteHandler, copyHandler } from './handlers/Clipboard.js';
 import * as Browser from './utils/Browser';
@@ -208,7 +209,7 @@ function Terminal(options) {
    * An array of all lines in the entire buffer, including the prompt. The lines are array of
    * characters which are 2-length arrays where [0] is an attribute and [1] is the character.
    */
-  this.lines = [];
+  this.lines = new Lines();
   var i = this.rows;
   while (i--) {
     this.lines.push(this.blankLine());
@@ -1078,7 +1079,7 @@ Terminal.prototype.refresh = function(start, end, queue) {
   for (; y <= end; y++) {
     row = y + this.ydisp;
 
-    line = this.lines[row];
+    line = this.lines.get(row);
     out = '';
 
     if (this.y === y - (this.ybase - this.ydisp)
@@ -1235,7 +1236,7 @@ Terminal.prototype.scroll = function() {
 
   if (++this.ybase === this.scrollback) {
     this.ybase = this.ybase / 2 | 0;
-    this.lines = this.lines.slice(-(this.ybase + this.rows) + 1);
+    this.lines = new Lines(this.lines.slice(-(this.ybase + this.rows) + 1));
   }
 
   if (!this.userScrolling) {
@@ -1442,15 +1443,15 @@ Terminal.prototype.write = function(data) {
               if (!ch_width && this.x) {
 
                 // dont overflow left
-                if (this.lines[row][this.x-1]) {
-                  if (!this.lines[row][this.x-1][2]) {
+                if (this.lines.get(row)[this.x-1]) {
+                  if (!this.lines.get(row)[this.x-1][2]) {
 
                     // found empty cell after fullwidth, need to go 2 cells back
-                    if (this.lines[row][this.x-2])
-                      this.lines[row][this.x-2][1] += ch;
+                    if (this.lines.get(row)[this.x-2])
+                      this.lines.get(row)[this.x-2][1] += ch;
 
                   } else {
-                    this.lines[row][this.x-1][1] += ch;
+                    this.lines.get(row)[this.x-1][1] += ch;
                   }
                   this.updateRange(this.y);
                 }
@@ -1482,24 +1483,24 @@ Terminal.prototype.write = function(data) {
                 for (var moves=0; moves<ch_width; ++moves) {
                   // remove last cell, if it's width is 0
                   // we have to adjust the second last cell as well
-                  var removed = this.lines[this.y + this.ybase].pop();
+                  var removed = this.lines.get(this.y + this.ybase).pop();
                   if (removed[2]===0
-                      && this.lines[row][this.cols-2]
-                      && this.lines[row][this.cols-2][2]===2)
-                    this.lines[row][this.cols-2] = [this.curAttr, ' ', 1];
+                      && this.lines.get(row)[this.cols-2]
+                      && this.lines.get(row)[this.cols-2][2]===2)
+                    this.lines.get(row)[this.cols-2] = [this.curAttr, ' ', 1];
 
                   // insert empty cell at cursor
-                  this.lines[row].splice(this.x, 0, [this.curAttr, ' ', 1]);
+                  this.lines.get(row).splice(this.x, 0, [this.curAttr, ' ', 1]);
                 }
               }
 
-              this.lines[row][this.x] = [this.curAttr, ch, ch_width];
+              this.lines.get(row)[this.x] = [this.curAttr, ch, ch_width];
               this.x++;
               this.updateRange(this.y);
 
               // fullwidth char - set next cell width to zero and advance cursor
               if (ch_width===2) {
-                this.lines[row][this.x] = [this.curAttr, '', 0];
+                this.lines.get(row)[this.x] = [this.curAttr, '', 0];
                 this.x++;
               }
             }
@@ -2864,15 +2865,15 @@ Terminal.prototype.resize = function(x, y) {
     ch = [this.defAttr, ' ', 1]; // does xterm use the default attr?
     i = this.lines.length;
     while (i--) {
-      while (this.lines[i].length < x) {
-        this.lines[i].push(ch);
+      while (this.lines.get(i).length < x) {
+        this.lines.get(i).push(ch);
       }
     }
   } else { // (j > x)
     i = this.lines.length;
     while (i--) {
-      while (this.lines[i].length > x) {
-        this.lines[i].pop();
+      while (this.lines.get(i).length > x) {
+        this.lines.get(i).pop();
       }
     }
   }
@@ -3027,9 +3028,8 @@ Terminal.prototype.nextStop = function(x) {
  * @param {number} y The line in which to operate.
  */
 Terminal.prototype.eraseRight = function(x, y) {
-  var line = this.lines[this.ybase + y]
-  , ch = [this.eraseAttr(), ' ', 1]; // xterm
-
+  var line = this.lines.get(this.ybase + y),
+      ch = [this.eraseAttr(), ' ', 1]; // xterm
 
   for (; x < this.cols; x++) {
     line[x] = ch;
@@ -3046,8 +3046,8 @@ Terminal.prototype.eraseRight = function(x, y) {
  * @param {number} y The line in which to operate.
  */
 Terminal.prototype.eraseLeft = function(x, y) {
-  var line = this.lines[this.ybase + y]
-  , ch = [this.eraseAttr(), ' ', 1]; // xterm
+  var line = this.lines.get(this.ybase + y),
+      ch = [this.eraseAttr(), ' ', 1]; // xterm
 
   x++;
   while (x--) line[x] = ch;
@@ -3063,7 +3063,7 @@ Terminal.prototype.clear = function() {
     // Don't clear if it's already clear
     return;
   }
-  this.lines = [this.lines[this.ybase + this.y]];
+  this.lines = new Lines([this.lines[this.ybase + this.y]]);
   this.ydisp = 0;
   this.ybase = 0;
   this.y = 0;
@@ -3642,8 +3642,8 @@ Terminal.prototype.insertChars = function(params) {
   ch = [this.eraseAttr(), ' ', 1]; // xterm
 
   while (param-- && j < this.cols) {
-    this.lines[row].splice(j++, 0, ch);
-    this.lines[row].pop();
+    this.lines.get(row).splice(j++, 0, ch);
+    this.lines.get(row).pop();
   }
 };
 
@@ -3756,8 +3756,8 @@ Terminal.prototype.deleteChars = function(params) {
   ch = [this.eraseAttr(), ' ', 1]; // xterm
 
   while (param--) {
-    this.lines[row].splice(this.x, 1);
-    this.lines[row].push(ch);
+    this.lines.get(row).splice(this.x, 1);
+    this.lines.get(row).push(ch);
   }
 };
 
@@ -3776,7 +3776,7 @@ Terminal.prototype.eraseChars = function(params) {
   ch = [this.eraseAttr(), ' ', 1]; // xterm
 
   while (param-- && j < this.cols) {
-    this.lines[row][j++] = ch;
+    this.lines.get(row)[j++] = ch;
   }
 };
 
@@ -4292,7 +4292,7 @@ Terminal.prototype.resetMode = function(params) {
       case 47: // normal screen buffer
       case 1047: // normal screen buffer - clearing it first
         if (this.normal) {
-          this.lines = this.normal.lines;
+          this.lines = new Lines(this.normal.lines);
           this.ybase = this.normal.ybase;
           this.ydisp = this.normal.ydisp;
           this.x = this.normal.x;
@@ -4439,9 +4439,9 @@ Terminal.prototype.cursorBackwardTab = function(params) {
  * CSI Ps b  Repeat the preceding graphic character Ps times (REP).
  */
 Terminal.prototype.repeatPrecedingCharacter = function(params) {
-  var param = params[0] || 1
-  , line = this.lines[this.ybase + this.y]
-  , ch = line[this.x - 1] || [this.defAttr, ' ', 1];
+  var param = params[0] || 1,
+      line = this.lines.get(this.ybase + this.y),
+      ch = line[this.x - 1] || [this.defAttr, ' ', 1];
 
   while (param--) line[this.x++] = ch;
 };
@@ -4675,7 +4675,7 @@ Terminal.prototype.setAttrInRectangle = function(params) {
   , i;
 
   for (; t < b + 1; t++) {
-    line = this.lines[this.ybase + t];
+    line = this.lines.get(this.ybase + t);
     for (i = l; i < r; i++) {
       line[i] = [attr, line[i][1]];
     }
@@ -4705,7 +4705,7 @@ Terminal.prototype.fillRectangle = function(params) {
   , i;
 
   for (; t < b + 1; t++) {
-    line = this.lines[this.ybase + t];
+    line = this.lines.get(this.ybase + t);
     for (i = l; i < r; i++) {
       line[i] = [line[i][0], String.fromCharCode(ch)];
     }
@@ -4757,7 +4757,7 @@ Terminal.prototype.eraseRectangle = function(params) {
   ch = [this.eraseAttr(), ' ', 1]; // xterm?
 
   for (; t < b + 1; t++) {
-    line = this.lines[this.ybase + t];
+    line = this.lines.get(this.ybase + t);
     for (i = l; i < r; i++) {
       line[i] = ch;
     }
@@ -4782,8 +4782,8 @@ Terminal.prototype.insertColumns = function() {
 
   while (param--) {
     for (i = this.ybase; i < l; i++) {
-      this.lines[i].splice(this.x + 1, 0, ch);
-      this.lines[i].pop();
+      this.lines.get(i).splice(this.x + 1, 0, ch);
+      this.lines.get(i).pop();
     }
   }
 
@@ -4804,8 +4804,8 @@ Terminal.prototype.deleteColumns = function() {
 
   while (param--) {
     for (i = this.ybase; i < l; i++) {
-      this.lines[i].splice(this.x, 1);
-      this.lines[i].push(ch);
+      this.lines.get(i).splice(this.x, 1);
+      this.lines.get(i).push(ch);
     }
   }
 

From e8ca00add54020c2f61915f0153b3af2d9ceb4b7 Mon Sep 17 00:00:00 2001
From: Paris Kasidiaris <paris@sourcelair.com>
Date: Wed, 14 Dec 2016 14:16:48 +0200
Subject: [PATCH 3/3] Fix tests

---
 src/test/escape-sequences-test.js |   2 +-
 src/test/test.js                  | 140 +++++++++++++++---------------
 src/xterm.js                      |   2 +-
 3 files changed, 72 insertions(+), 72 deletions(-)

diff --git a/src/test/escape-sequences-test.js b/src/test/escape-sequences-test.js
index 2eb6016556..b251741eff 100644
--- a/src/test/escape-sequences-test.js
+++ b/src/test/escape-sequences-test.js
@@ -59,7 +59,7 @@ function terminalToString(term) {
   for (var line=0; line<term.rows; ++line) {
     line_s = '';
     for (var cell=0; cell<term.cols; ++cell) {
-      line_s += term.lines[line][cell][1];
+      line_s += term.lines.get(line)[cell][1];
     }
     // rtrim empty cells as xterm does
     line_s = line_s.replace(/\s+$/, '');
diff --git a/src/test/test.js b/src/test/test.js
index d8e931fbdd..d006970a91 100644
--- a/src/test/test.js
+++ b/src/test/test.js
@@ -48,15 +48,15 @@ describe('xterm.js', function() {
 
   describe('clear', function() {
     it('should clear a buffer equal to rows', function() {
-      var promptLine = xterm.lines[xterm.ybase + xterm.y];
+      var promptLine = xterm.lines.get(xterm.ybase + xterm.y);
       xterm.clear();
       assert.equal(xterm.y, 0);
       assert.equal(xterm.ybase, 0);
       assert.equal(xterm.ydisp, 0);
       assert.equal(xterm.lines.length, xterm.rows);
-      assert.deepEqual(xterm.lines[0], promptLine);
+      assert.deepEqual(xterm.lines.get(0), promptLine);
       for (var i = 1; i < xterm.rows; i++) {
-        assert.deepEqual(xterm.lines[0], xterm.blankLine());
+        assert.deepEqual(xterm.lines.get(0), xterm.blankLine());
       }
     });
     it('should clear a buffer larger than rows', function() {
@@ -65,28 +65,28 @@ describe('xterm.js', function() {
         xterm.write('test\n');
       }
 
-      var promptLine = xterm.lines[xterm.ybase + xterm.y];
+      var promptLine = xterm.lines.get(xterm.ybase + xterm.y);
       xterm.clear();
       assert.equal(xterm.y, 0);
       assert.equal(xterm.ybase, 0);
       assert.equal(xterm.ydisp, 0);
       assert.equal(xterm.lines.length, xterm.rows);
-      assert.deepEqual(xterm.lines[0], promptLine);
+      assert.deepEqual(xterm.lines.get(0), promptLine);
       for (var i = 1; i < xterm.rows; i++) {
-        assert.deepEqual(xterm.lines[i], xterm.blankLine());
+        assert.deepEqual(xterm.lines.get(i), xterm.blankLine());
       }
     });
     it('should not break the prompt when cleared twice', function() {
-      var promptLine = xterm.lines[xterm.ybase + xterm.y];
+      var promptLine = xterm.lines.get(xterm.ybase + xterm.y);
       xterm.clear();
       xterm.clear();
       assert.equal(xterm.y, 0);
       assert.equal(xterm.ybase, 0);
       assert.equal(xterm.ydisp, 0);
       assert.equal(xterm.lines.length, xterm.rows);
-      assert.deepEqual(xterm.lines[0], promptLine);
+      assert.deepEqual(xterm.lines.get(0), promptLine);
       for (var i = 1; i < xterm.rows; i++) {
-        assert.deepEqual(xterm.lines[i], xterm.blankLine());
+        assert.deepEqual(xterm.lines.get(i), xterm.blankLine());
       }
     });
   });
@@ -524,11 +524,11 @@ describe('xterm.js', function() {
       var high = String.fromCharCode(0xD800);
       for (var i=0xDC00; i<=0xDCFF; ++i) {
         xterm.write(high + String.fromCharCode(i));
-        var tchar = xterm.lines[0][0];
+        var tchar = xterm.lines.get(0)[0];
         expect(tchar[1]).eql(high + String.fromCharCode(i));
         expect(tchar[1].length).eql(2);
         expect(tchar[2]).eql(1);
-        expect(xterm.lines[0][1][1]).eql(' ');
+        expect(xterm.lines.get(0)[1][1]).eql(' ');
         xterm.reset();
       }
     });
@@ -537,9 +537,9 @@ describe('xterm.js', function() {
       for (var i=0xDC00; i<=0xDCFF; ++i) {
         xterm.x = xterm.cols - 1;
         xterm.write(high + String.fromCharCode(i));
-        expect(xterm.lines[0][xterm.x-1][1]).eql(high + String.fromCharCode(i));
-        expect(xterm.lines[0][xterm.x-1][1].length).eql(2);
-        expect(xterm.lines[1][0][1]).eql(' ');
+        expect(xterm.lines.get(0)[xterm.x-1][1]).eql(high + String.fromCharCode(i));
+        expect(xterm.lines.get(0)[xterm.x-1][1].length).eql(2);
+        expect(xterm.lines.get(1)[0][1]).eql(' ');
         xterm.reset();
       }
     });
@@ -549,10 +549,10 @@ describe('xterm.js', function() {
         xterm.x = xterm.cols - 1;
         xterm.wraparoundMode = true;
         xterm.write('a' + high + String.fromCharCode(i));
-        expect(xterm.lines[0][xterm.cols-1][1]).eql('a');
-        expect(xterm.lines[1][0][1]).eql(high + String.fromCharCode(i));
-        expect(xterm.lines[1][0][1].length).eql(2);
-        expect(xterm.lines[1][1][1]).eql(' ');
+        expect(xterm.lines.get(0)[xterm.cols-1][1]).eql('a');
+        expect(xterm.lines.get(1)[0][1]).eql(high + String.fromCharCode(i));
+        expect(xterm.lines.get(1)[0][1].length).eql(2);
+        expect(xterm.lines.get(1)[1][1]).eql(' ');
         xterm.reset();
       }
     });
@@ -562,9 +562,9 @@ describe('xterm.js', function() {
         xterm.x = xterm.cols - 1;
         xterm.wraparoundMode = false;
         xterm.write('a' + high + String.fromCharCode(i));
-        expect(xterm.lines[0][xterm.cols-1][1]).eql(high + String.fromCharCode(i));
-        expect(xterm.lines[0][xterm.cols-1][1].length).eql(2);
-        expect(xterm.lines[1][1][1]).eql(' ');
+        expect(xterm.lines.get(0)[xterm.cols-1][1]).eql(high + String.fromCharCode(i));
+        expect(xterm.lines.get(0)[xterm.cols-1][1].length).eql(2);
+        expect(xterm.lines.get(1)[1][1]).eql(' ');
         xterm.reset();
       }
     });
@@ -573,11 +573,11 @@ describe('xterm.js', function() {
       for (var i=0xDC00; i<=0xDCFF; ++i) {
         xterm.write(high);
         xterm.write(String.fromCharCode(i));
-        var tchar = xterm.lines[0][0];
+        var tchar = xterm.lines.get(0)[0];
         expect(tchar[1]).eql(high + String.fromCharCode(i));
         expect(tchar[1].length).eql(2);
         expect(tchar[2]).eql(1);
-        expect(xterm.lines[0][1][1]).eql(' ');
+        expect(xterm.lines.get(0)[1][1]).eql(' ');
         xterm.reset();
       }
     });
@@ -586,30 +586,30 @@ describe('xterm.js', function() {
   describe('unicode - combining characters', function() {
     it('café', function () {
       xterm.write('cafe\u0301');
-      expect(xterm.lines[0][3][1]).eql('e\u0301');
-      expect(xterm.lines[0][3][1].length).eql(2);
-      expect(xterm.lines[0][3][2]).eql(1);
+      expect(xterm.lines.get(0)[3][1]).eql('e\u0301');
+      expect(xterm.lines.get(0)[3][1].length).eql(2);
+      expect(xterm.lines.get(0)[3][2]).eql(1);
     });
     it('café - end of line', function() {
       xterm.x = xterm.cols - 1 - 3;
       xterm.write('cafe\u0301');
-      expect(xterm.lines[0][xterm.cols-1][1]).eql('e\u0301');
-      expect(xterm.lines[0][xterm.cols-1][1].length).eql(2);
-      expect(xterm.lines[0][xterm.cols-1][2]).eql(1);
-      expect(xterm.lines[0][1][1]).eql(' ');
-      expect(xterm.lines[0][1][1].length).eql(1);
-      expect(xterm.lines[0][1][2]).eql(1);
+      expect(xterm.lines.get(0)[xterm.cols-1][1]).eql('e\u0301');
+      expect(xterm.lines.get(0)[xterm.cols-1][1].length).eql(2);
+      expect(xterm.lines.get(0)[xterm.cols-1][2]).eql(1);
+      expect(xterm.lines.get(0)[1][1]).eql(' ');
+      expect(xterm.lines.get(0)[1][1].length).eql(1);
+      expect(xterm.lines.get(0)[1][2]).eql(1);
     });
     it('multiple combined é', function() {
       xterm.wraparoundMode = true;
       xterm.write(Array(100).join('e\u0301'));
       for (var i=0; i<xterm.cols; ++i) {
-        var tchar = xterm.lines[0][i];
+        var tchar = xterm.lines.get(0)[i];
         expect(tchar[1]).eql('e\u0301');
         expect(tchar[1].length).eql(2);
         expect(tchar[2]).eql(1);
       }
-      tchar = xterm.lines[1][0];
+      tchar = xterm.lines.get(1)[0];
       expect(tchar[1]).eql('e\u0301');
       expect(tchar[1].length).eql(2);
       expect(tchar[2]).eql(1);
@@ -618,12 +618,12 @@ describe('xterm.js', function() {
       xterm.wraparoundMode = true;
       xterm.write(Array(100).join('\uD800\uDC00\u0301'));
       for (var i=0; i<xterm.cols; ++i) {
-        var tchar = xterm.lines[0][i];
+        var tchar = xterm.lines.get(0)[i];
         expect(tchar[1]).eql('\uD800\uDC00\u0301');
         expect(tchar[1].length).eql(3);
         expect(tchar[2]).eql(1);
       }
-      tchar = xterm.lines[1][0];
+      tchar = xterm.lines.get(1)[0];
       expect(tchar[1]).eql('\uD800\uDC00\u0301');
       expect(tchar[1].length).eql(3);
       expect(tchar[2]).eql(1);
@@ -646,7 +646,7 @@ describe('xterm.js', function() {
       xterm.wraparoundMode = true;
       xterm.write(Array(50).join('￥'));
       for (var i=0; i<xterm.cols; ++i) {
-        var tchar = xterm.lines[0][i];
+        var tchar = xterm.lines.get(0)[i];
         if (i % 2) {
           expect(tchar[1]).eql('');
           expect(tchar[1].length).eql(0);
@@ -657,7 +657,7 @@ describe('xterm.js', function() {
           expect(tchar[2]).eql(2);
         }
       }
-      tchar = xterm.lines[1][0];
+      tchar = xterm.lines.get(1)[0];
       expect(tchar[1]).eql('￥');
       expect(tchar[1].length).eql(1);
       expect(tchar[2]).eql(2);
@@ -667,7 +667,7 @@ describe('xterm.js', function() {
       xterm.x = 1;
       xterm.write(Array(50).join('￥'));
       for (var i=1; i<xterm.cols-1; ++i) {
-        var tchar = xterm.lines[0][i];
+        var tchar = xterm.lines.get(0)[i];
         if (!(i % 2)) {
           expect(tchar[1]).eql('');
           expect(tchar[1].length).eql(0);
@@ -678,11 +678,11 @@ describe('xterm.js', function() {
           expect(tchar[2]).eql(2);
         }
       }
-      tchar = xterm.lines[0][xterm.cols-1];
+      tchar = xterm.lines.get(0)[xterm.cols-1];
       expect(tchar[1]).eql(' ');
       expect(tchar[1].length).eql(1);
       expect(tchar[2]).eql(1);
-      tchar = xterm.lines[1][0];
+      tchar = xterm.lines.get(1)[0];
       expect(tchar[1]).eql('￥');
       expect(tchar[1].length).eql(1);
       expect(tchar[2]).eql(2);
@@ -692,7 +692,7 @@ describe('xterm.js', function() {
       xterm.x = 1;
       xterm.write(Array(50).join('￥\u0301'));
       for (var i=1; i<xterm.cols-1; ++i) {
-        var tchar = xterm.lines[0][i];
+        var tchar = xterm.lines.get(0)[i];
         if (!(i % 2)) {
           expect(tchar[1]).eql('');
           expect(tchar[1].length).eql(0);
@@ -703,11 +703,11 @@ describe('xterm.js', function() {
           expect(tchar[2]).eql(2);
         }
       }
-      tchar = xterm.lines[0][xterm.cols-1];
+      tchar = xterm.lines.get(0)[xterm.cols-1];
       expect(tchar[1]).eql(' ');
       expect(tchar[1].length).eql(1);
       expect(tchar[2]).eql(1);
-      tchar = xterm.lines[1][0];
+      tchar = xterm.lines.get(1)[0];
       expect(tchar[1]).eql('￥\u0301');
       expect(tchar[1].length).eql(2);
       expect(tchar[2]).eql(2);
@@ -716,7 +716,7 @@ describe('xterm.js', function() {
       xterm.wraparoundMode = true;
       xterm.write(Array(50).join('￥\u0301'));
       for (var i=0; i<xterm.cols; ++i) {
-        var tchar = xterm.lines[0][i];
+        var tchar = xterm.lines.get(0)[i];
         if (i % 2) {
           expect(tchar[1]).eql('');
           expect(tchar[1].length).eql(0);
@@ -727,7 +727,7 @@ describe('xterm.js', function() {
           expect(tchar[2]).eql(2);
         }
       }
-      tchar = xterm.lines[1][0];
+      tchar = xterm.lines.get(1)[0];
       expect(tchar[1]).eql('￥\u0301');
       expect(tchar[1].length).eql(2);
       expect(tchar[2]).eql(2);
@@ -737,7 +737,7 @@ describe('xterm.js', function() {
       xterm.x = 1;
       xterm.write(Array(50).join('\ud843\ude6d\u0301'));
       for (var i=1; i<xterm.cols-1; ++i) {
-        var tchar = xterm.lines[0][i];
+        var tchar = xterm.lines.get(0)[i];
         if (!(i % 2)) {
           expect(tchar[1]).eql('');
           expect(tchar[1].length).eql(0);
@@ -748,11 +748,11 @@ describe('xterm.js', function() {
           expect(tchar[2]).eql(2);
         }
       }
-      tchar = xterm.lines[0][xterm.cols-1];
+      tchar = xterm.lines.get(0)[xterm.cols-1];
       expect(tchar[1]).eql(' ');
       expect(tchar[1].length).eql(1);
       expect(tchar[2]).eql(1);
-      tchar = xterm.lines[1][0];
+      tchar = xterm.lines.get(1)[0];
       expect(tchar[1]).eql('\ud843\ude6d\u0301');
       expect(tchar[1].length).eql(3);
       expect(tchar[2]).eql(2);
@@ -761,7 +761,7 @@ describe('xterm.js', function() {
       xterm.wraparoundMode = true;
       xterm.write(Array(50).join('\ud843\ude6d\u0301'));
       for (var i=0; i<xterm.cols; ++i) {
-        var tchar = xterm.lines[0][i];
+        var tchar = xterm.lines.get(0)[i];
         if (i % 2) {
           expect(tchar[1]).eql('');
           expect(tchar[1].length).eql(0);
@@ -772,7 +772,7 @@ describe('xterm.js', function() {
           expect(tchar[2]).eql(2);
         }
       }
-      tchar = xterm.lines[1][0];
+      tchar = xterm.lines.get(1)[0];
       expect(tchar[1]).eql('\ud843\ude6d\u0301');
       expect(tchar[1].length).eql(3);
       expect(tchar[2]).eql(2);
@@ -786,11 +786,11 @@ describe('xterm.js', function() {
       xterm.y = 0;
       xterm.insertMode = true;
       xterm.write('abcde');
-      expect(xterm.lines[0].length).eql(xterm.cols);
-      expect(xterm.lines[0][10][1]).eql('a');
-      expect(xterm.lines[0][14][1]).eql('e');
-      expect(xterm.lines[0][15][1]).eql('0');
-      expect(xterm.lines[0][79][1]).eql('4');
+      expect(xterm.lines.get(0).length).eql(xterm.cols);
+      expect(xterm.lines.get(0)[10][1]).eql('a');
+      expect(xterm.lines.get(0)[14][1]).eql('e');
+      expect(xterm.lines.get(0)[15][1]).eql('0');
+      expect(xterm.lines.get(0)[79][1]).eql('4');
     });
     it('fullwidth - insert', function() {
       xterm.write(Array(9).join('0123456789').slice(-80));
@@ -798,12 +798,12 @@ describe('xterm.js', function() {
       xterm.y = 0;
       xterm.insertMode = true;
       xterm.write('￥￥￥');
-      expect(xterm.lines[0].length).eql(xterm.cols);
-      expect(xterm.lines[0][10][1]).eql('￥');
-      expect(xterm.lines[0][11][1]).eql('');
-      expect(xterm.lines[0][14][1]).eql('￥');
-      expect(xterm.lines[0][15][1]).eql('');
-      expect(xterm.lines[0][79][1]).eql('3');
+      expect(xterm.lines.get(0).length).eql(xterm.cols);
+      expect(xterm.lines.get(0)[10][1]).eql('￥');
+      expect(xterm.lines.get(0)[11][1]).eql('');
+      expect(xterm.lines.get(0)[14][1]).eql('￥');
+      expect(xterm.lines.get(0)[15][1]).eql('');
+      expect(xterm.lines.get(0)[79][1]).eql('3');
     });
     it('fullwidth - right border', function() {
       xterm.write(Array(41).join('￥'));
@@ -811,15 +811,15 @@ describe('xterm.js', function() {
       xterm.y = 0;
       xterm.insertMode = true;
       xterm.write('a');
-      expect(xterm.lines[0].length).eql(xterm.cols);
-      expect(xterm.lines[0][10][1]).eql('a');
-      expect(xterm.lines[0][11][1]).eql('￥');
-      expect(xterm.lines[0][79][1]).eql(' ');  // fullwidth char got replaced
+      expect(xterm.lines.get(0).length).eql(xterm.cols);
+      expect(xterm.lines.get(0)[10][1]).eql('a');
+      expect(xterm.lines.get(0)[11][1]).eql('￥');
+      expect(xterm.lines.get(0)[79][1]).eql(' ');  // fullwidth char got replaced
       xterm.write('b');
-      expect(xterm.lines[0].length).eql(xterm.cols);
-      expect(xterm.lines[0][11][1]).eql('b');
-      expect(xterm.lines[0][12][1]).eql('￥');
-      expect(xterm.lines[0][79][1]).eql('');  // empty cell after fullwidth
+      expect(xterm.lines.get(0).length).eql(xterm.cols);
+      expect(xterm.lines.get(0)[11][1]).eql('b');
+      expect(xterm.lines.get(0)[12][1]).eql('￥');
+      expect(xterm.lines.get(0)[79][1]).eql('');  // empty cell after fullwidth
     });
   });
 });
diff --git a/src/xterm.js b/src/xterm.js
index 3e88ec51ea..a4bb875886 100644
--- a/src/xterm.js
+++ b/src/xterm.js
@@ -3063,7 +3063,7 @@ Terminal.prototype.clear = function() {
     // Don't clear if it's already clear
     return;
   }
-  this.lines = new Lines([this.lines[this.ybase + this.y]]);
+  this.lines = new Lines([this.lines.get(this.ybase + this.y)]);
   this.ydisp = 0;
   this.ybase = 0;
   this.y = 0;