Introduce new Buffer and BufferSet classes

src/Buffer.ts

@@ -0,0 +1,23 @@
+/**
+ * @license MIT
+ */
+
+import { ITerminal } from './Interfaces';
+import { CircularList } from './utils/CircularList';
+
+export class Buffer {
+  private _lines: CircularList<any>;
+  private _ybase: number;
+  private _ydisp: number;
+  private _y: number;
+  private _x: number;
+  private _tabs: any;
+
+  constructor(private terminal: ITerminal) {
+    this._lines = new CircularList(this.terminal.scrollback);
+  }
+
+  public get lines(): CircularList {
+    return this._lines;
+  }
+}

src/BufferSet.ts

@@ -0,0 +1,44 @@
+/**
+ * @license MIT
+ */
+
+import { ITerminal } from './Interfaces';
+import { Buffer } from './Buffer';
+
+export class BufferSet {
+  private _normal: Buffer;
+  private _alt: Buffer;
+  private _activeBuffer: Buffer;
+
+  constructor(private _terminal: ITerminal) {
+    this._normal = new Buffer(this._terminal);
+    this._alt = new Buffer(this._terminal);
+    this._activeBuffer = this._normal;
+  }
+
+  public get alt(): Buffer {
+    return this._alt;
+  }
+
+  public get active(): Buffer {
+    return this._activeBuffer;
+  }
+
+  public get normal(): Buffer {
+    return this._normal;
+  }
+
+  private resetTerminal() {
+    this._terminal.reset();
+    this._terminal.viewport.syncScrollArea();
+    this._terminal.showCursor();
+  }
+
+  public activateNormalBuffer(): void {
+    this._activeBuffer = this._normal;
+  }
+
+  public activateAltBuffer(): void {
+    this._activeBuffer = this._normal;
+  }
+}

src/Interfaces.ts

@@ -37,6 +37,7 @@ export interface ITerminal {
   x: number;
   y: number;
   defAttr: number;
+  scrollback: number;
 
   /**
    * Emit the 'data' event and populate the given data.

src/xterm.js

@@ -10,6 +10,7 @@
  * @license MIT
  */
 
+import { BufferSet } from './BufferSet';
 import { CompositionHelper } from './CompositionHelper';
 import { EventEmitter } from './EventEmitter';
 import { Viewport } from './Viewport';
@@ -243,6 +244,7 @@ function Terminal(options) {
   // leftover surrogate high from previous write invocation
   this.surrogate_high = '';
 
+  this.buffers = new BufferSet(this);
   /**
    * 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.