Expose API to clear the terminal

Fixes #173

src/xterm.js

@@ -3054,6 +3054,20 @@ Terminal.prototype.eraseLeft = function(x, y) {
   this.updateRange(y);
 };
 
+/**
+ * Clears the entire buffer, making the prompt line the new first line.
+ */
+Terminal.prototype.clear = function() {
+  this.ydisp = 0;
+  this.ybase = 0;
+  this.y = 0;
+  this.lines = [this.lines[this.lines.length - 1]];
+  for (var i = 1; i < this.rows; i++) {
+    this.lines.push(this.blankLine());
+  }
+  this.refresh(0, this.rows - 1);
+  this.emit('scroll', this.ydisp);
+};
 
 /**
  * Erase all content in the given line

test/test.js

@@ -24,6 +24,38 @@ describe('xterm.js', function() {
     });
   });
 
+  describe('clear', function() {
+    it('should clear a buffer equal to rows', function() {
+      var promptLine = xterm.lines[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);
+      for (var i = 1; i < xterm.rows; i++) {
+        assert.deepEqual(xterm.lines[0], xterm.blankLine());
+      }
+    });
+    it('should clear a buffer larger than rows', function() {
+      // Fill the buffer with dummy rows
+      for (var i = 0; i < xterm.rows * 2; i++) {
+        xterm.write('test\n');
+      }
+
+      var promptLine = xterm.lines[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);
+      for (var i = 1; i < xterm.rows; i++) {
+        assert.deepEqual(xterm.lines[0], xterm.blankLine());
+      }
+    });
+  });
+
   describe('evaluateKeyEscapeSequence', function() {
     it('should return the correct escape sequence for unmodified keys', function() {
       // Backspace