Support buffers with scrollback of 0, force alt as 0

Fixes #802

src/BufferSet.ts

@@ -21,9 +21,9 @@ export class BufferSet extends EventEmitter implements IBufferSet {
    */
   constructor(private _terminal: ITerminal) {
     super();
-    this._normal = new Buffer(this._terminal);
+    this._normal = new Buffer(this._terminal, false);
     this._normal.fillViewportRows();
-    this._alt = new Buffer(this._terminal);
+    this._alt = new Buffer(this._terminal, true);
     this._activeBuffer = this._normal;
   }
 
@@ -71,22 +71,10 @@ export class BufferSet extends EventEmitter implements IBufferSet {
     // Since the alt buffer is always cleared when the normal buffer is
     // activated, we want to fill it when switching to it.
     this._alt.fillViewportRows();
-
     this._activeBuffer = this._alt;
     this.emit('activate', this._alt);
   }
 
-  /**
-   * Refreshes the max length of the buffer set, this should be called whenever
-   * terminal rows or scrollback changes.
-   * @param rows The number of terminal rows.
-   */
-  public refreshMaxLength(rows: number): void {
-    this._normal.lines.maxLength = rows + this._terminal.options.scrollback;
-    // TODO: The alt buffer should never have scrollback, see https://github.com/sourcelair/xterm.js/issues/802
-    this._alt.lines.maxLength = rows + this._terminal.options.scrollback;
-  }
-
   /**
    * Resizes both normal and alt buffers, adjusting their data accordingly.
    * @param newCols The new number of columns.
@@ -95,6 +83,5 @@ export class BufferSet extends EventEmitter implements IBufferSet {
   public resize(newCols: number, newRows: number): void {
     this._normal.resize(newCols, newRows);
     this._alt.resize(newCols, newRows);
-    this.refreshMaxLength(newRows);
   }
 }