Implement scrollPages, scrollToTop, scrollToBottom and add scroll tests

src/xterm.js

@@ -1307,6 +1307,28 @@ Terminal.prototype.scrollDisp = function(disp, suppressScrollEvent) {
   this.refresh(0, this.rows - 1);
 };
 
+/**
+ * Scroll the display of the terminal by a number of pages.
+ * @param {number} pageCount The number of pages to scroll.
+ */
+Terminal.prototype.scrollPages = function(pageCount) {
+  this.scrollDisp(pageCount * (this.rows - 1));
+}
+
+/**
+ * Scrolls the display of the terminal to the top.
+ */
+Terminal.prototype.scrollToTop = function() {
+  this.scrollDisp(-this.ydisp);
+}
+
+/**
+ * Scrolls the display of the terminal to the bottom.
+ */
+Terminal.prototype.scrollToBottom = function() {
+  this.scrollDisp(this.ybase - this.ydisp);
+}
+
 /**
  * Writes text to the terminal.
  * @param {string} text The text to write to the terminal.

test/test.js

@@ -88,6 +88,101 @@ describe('xterm.js', function() {
     });
   });
 
+  describe('scroll', function() {
+    describe('scrollDisp', function() {
+      var startYDisp;
+      beforeEach(function() {
+        for (var i = 0; i < xterm.rows * 2; i++) {
+          xterm.writeln('test');
+        }
+        startYDisp = xterm.rows + 1;
+      });
+      it('should scroll a single line', function() {
+        assert.equal(xterm.ydisp, startYDisp);
+        xterm.scrollDisp(-1);
+        assert.equal(xterm.ydisp, startYDisp - 1);
+        xterm.scrollDisp(1);
+        assert.equal(xterm.ydisp, startYDisp);
+      });
+      it('should scroll multiple lines', function() {
+        assert.equal(xterm.ydisp, startYDisp);
+        xterm.scrollDisp(-5);
+        assert.equal(xterm.ydisp, startYDisp - 5);
+        xterm.scrollDisp(5);
+        assert.equal(xterm.ydisp, startYDisp);
+      });
+      it('should not scroll beyond the bounds of the buffer', function() {
+        assert.equal(xterm.ydisp, startYDisp);
+        xterm.scrollDisp(1);
+        assert.equal(xterm.ydisp, startYDisp);
+        for (var i = 0; i < startYDisp; i++) {
+          xterm.scrollDisp(-1);
+        }
+        assert.equal(xterm.ydisp, 0);
+        xterm.scrollDisp(-1);
+        assert.equal(xterm.ydisp, 0);
+      });
+    });
+
+    describe('scrollPages', function() {
+      var startYDisp;
+      beforeEach(function() {
+        for (var i = 0; i < xterm.rows * 3; i++) {
+          xterm.writeln('test');
+        }
+        startYDisp = (xterm.rows * 2) + 1;
+      });
+      it('should scroll a single page', function() {
+        assert.equal(xterm.ydisp, startYDisp);
+        xterm.scrollPages(-1);
+        assert.equal(xterm.ydisp, startYDisp - (xterm.rows - 1));
+        xterm.scrollPages(1);
+        assert.equal(xterm.ydisp, startYDisp);
+      });
+      it('should scroll a multiple pages', function() {
+        assert.equal(xterm.ydisp, startYDisp);
+        xterm.scrollPages(-2);
+        assert.equal(xterm.ydisp, startYDisp - (xterm.rows - 1) * 2);
+        xterm.scrollPages(2);
+        assert.equal(xterm.ydisp, startYDisp);
+      });
+    });
+
+    describe('scrollToTop', function() {
+      beforeEach(function() {
+        for (var i = 0; i < xterm.rows * 3; i++) {
+          xterm.writeln('test');
+        }
+      });
+      it('should scroll to the top', function() {
+        assert.notEqual(xterm.ydisp, 0);
+        xterm.scrollToTop();
+        assert.equal(xterm.ydisp, 0);
+      });
+    });
+
+    describe('scrollToBottom', function() {
+      var startYDisp;
+      beforeEach(function() {
+        for (var i = 0; i < xterm.rows * 3; i++) {
+          xterm.writeln('test');
+        }
+        startYDisp = (xterm.rows * 2) + 1;
+      });
+      it('should scroll to the bottom', function() {
+        xterm.scrollDisp(-1);
+        xterm.scrollToBottom();
+        assert.equal(xterm.ydisp, startYDisp);
+        xterm.scrollPages(-1);
+        xterm.scrollToBottom();
+        assert.equal(xterm.ydisp, startYDisp);
+        xterm.scrollToTop();
+        xterm.scrollToBottom();
+        assert.equal(xterm.ydisp, startYDisp);
+      });
+    });
+  });
+
   describe('evaluateKeyEscapeSequence', function() {
     it('should return the correct escape sequence for unmodified keys', function() {
       // Backspace