4.0.6

* patch(fix #85): fixes xss vulnerability

* patch(fix #85): better XSS fix

.gitignore

@@ -1,3 +1,4 @@
 /node_modules
 /lib
 mergely-*.tgz
+package-lock.json

CHANGES.md

@@ -1,5 +1,17 @@
 # Changes
 
+## 4.0.6
+
+* #89: fixes missing merge buttons
+
+## 4.0.5
+
+* #85: fixes XSS vulnerability with DOM id
+
+## 4.0.2
+
+* #83: fixes poor rendering performance
+
 ## 4.0.0
 
 ### Breaking changes

package.json

@@ -1,6 +1,6 @@
 {
   "name": "mergely",
-  "version": "4.0.2",
+  "version": "4.0.6",
   "description": "A javascript UI for diff/merge",
   "directories": {
     "doc": "doc",

src/mergely.js

@@ -54,8 +54,8 @@ Mgly.sizeOf = function(obj) {
 };
 
 Mgly.LCS = function(x, y) {
-	this.x = x.replace(/[ ]{1}/g, '\n');
-	this.y = y.replace(/[ ]{1}/g, '\n');
+	this.x = (x && x.replace(/[ ]{1}/g, '\n')) || '';
+	this.y = (y && y.replace(/[ ]{1}/g, '\n')) || '';
 };
 
 jQuery.extend(Mgly.LCS.prototype, {
@@ -461,11 +461,11 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 			lineNumbers: this.settings.line_numbers
 		};
 		var lhs_gutters = [];
-		if (this.lhs_cmsettings.line_numbers) {
+		if (this.lhs_cmsettings.lineNumbers) {
 			lhs_gutters = ['merge', 'CodeMirror-linenumbers']
 		}
 		var rhs_gutters = [];
-		if (this.rhs_cmsettings.line_numbers) {
+		if (this.rhs_cmsettings.lineNumbers) {
 			rhs_gutters = ['merge', 'CodeMirror-linenumbers']
 		}
 		jQuery.extend(true, this.lhs_cmsettings, this.settings.cmsettings, { gutters: lhs_gutters }, this.settings);
@@ -659,6 +659,13 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 	bind: function(el) {
 		this.element.hide();
 		this.id = jQuery(el).attr('id');
+		try {
+			// ensure the id is valid for jQuery
+			jQuery(`#${this.id}`);
+		} catch (ex) {
+			console.error(`jQuery failed to find mergely: #${this.id}`);
+			return;
+		}
 		this.changed_timeout = null;
 		this.chfns = {};
 		this.chfns[this.id + '-lhs'] = [];
@@ -676,7 +683,7 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 		}
 		else {
 			// homebrew
-			var style = 'opacity:0.4;width:10px;height:15px;background-color:#888;cursor:pointer;text-align:center;color:#eee;border:1px solid #222;margin-right:5px;margin-top: -2px;';
+			var style = 'opacity:0.6;height:16px;background-color:#bfbfbf;cursor:pointer;text-align:center;color:#eee;border:1px solid #848484;margin-right:5px;margin-top:-2px;';
 			merge_lhs_button = '<div style="' + style + '" title="Merge left">&lt;</div>';
 			merge_rhs_button = '<div style="' + style + '" title="Merge right">&gt;</div>';
 		}
@@ -686,17 +693,32 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 		// create the textarea and canvas elements
 		var height = '10px';
 		var width = '10px';
-		this.element.append(jQuery('<div id="mergely-splash">'));
-		this.element.append(jQuery('<div class="mergely-margin" style="height: ' + height + '"><canvas id="' + this.id + '-lhs-margin" width="8px" height="' + height + '"></canvas></div>'));
-		this.element.append(jQuery('<div style="position:relative;width:' + width + '; height:' + height + '" id="' + this.id + '-editor-lhs" class="mergely-column"><textarea style="" id="' + this.id + '-lhs"></textarea></div>'));
-		this.element.append(jQuery('<div class="mergely-canvas" style="height: ' + height + '"><canvas id="' + this.id + '-lhs-' + this.id + '-rhs-canvas" style="width:28px" width="28px" height="' + height + '"></canvas></div>'));
-		var rmargin = jQuery('<div class="mergely-margin" style="height: ' + height + '"><canvas id="' + this.id + '-rhs-margin" width="8px" height="' + height + '"></canvas></div>');
+
+		var splash = jQuery('<div id="mergely-splash">');
+		var canvasLhs = jQuery(`<div class="mergely-margin" style="height: '${height}'"><canvas id="lhs-margin" width="8px" height="'${height}'"></canvas></div>`);
+		canvasLhs.find('#lhs-margin').attr('id', `${this.id}-lhs-margin`);
+		var editorLhs = jQuery(`<div style="position:relative;width:'${width}'; height:'${height}'" id="editor-lhs" class="mergely-column"><textarea id="text-lhs"></textarea></div>`);
+		editorLhs.eq(0).attr('id', `${this.id}-editor-lhs`);
+		editorLhs.find('#text-lhs').attr('id', `${this.id}-lhs`);
+		var canvasMid = jQuery(`<div class="mergely-canvas" style="height: '${height}'"><canvas id="lhs-rhs-canvas" style="width:28px" width="28px" height="'${height}'"></canvas></div>`);
+		canvasMid.find('#mergely-canvas').attr('id', `${this.id}-mergely-canvas`);
+		canvasMid.find('#lhs-rhs-canvas').attr('id', `${this.id}-lhs-${this.id}-rhs-canvas`);
+
+		this.element.append(splash);
+		this.element.append(canvasLhs);
+		this.element.append(editorLhs);
+		this.element.append(canvasMid);
+		var canvasRhs = jQuery(`<div class="mergely-margin" style="height: '${height}'"><canvas id="rhs-margin" width="8px" height="'${height}'"></canvas></div>`);
+		canvasRhs.find('#rhs-margin').attr('id', `${this.id}-rhs-margin`);
 		if (this.settings.rhs_margin == 'left') {
-			this.element.append(rmargin);
+			this.element.append(canvasRhs);
 		}
-		this.element.append(jQuery('<div style="width:' + width + '; height:' + height + '" id="' + this.id + '-editor-rhs" class="mergely-column"><textarea style="" id="' + this.id + '-rhs"></textarea></div>'));
+		var editorRhs = jQuery(`<div style="width:'${width}'; height:'${height}'" id="editor-rhs" class="mergely-column"><textarea id="text-rhs"></textarea></div>`);
+		editorRhs.eq(0).attr('id', `${this.id}-editor-rhs`);
+		editorRhs.find('#text-rhs').attr('id', `${this.id}-rhs`);
+		this.element.append(editorRhs);
 		if (this.settings.rhs_margin != 'left') {
-			this.element.append(rmargin);
+			this.element.append(canvasRhs);
 		}
 		if (!this.settings.sidebar) {
 			this.element.find('.mergely-margin').css({display: 'none'});
@@ -734,32 +756,42 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 			});
 		}
 
+		// check initialization
+		var rhstx;
+		try {
+			rhstx = this.element.find(`#${this.id}-rhs`).get(0);
+		} catch (ex) {
+		}
+		if (!rhstx) {
+			console.error('rhs textarea not defined - Mergely not initialized properly');
+			return;
+		}
+		var lhstx;
+		try {
+			lhstx = this.element.find(`#${this.id}-lhs`).get(0);
+		} catch (ex) {
+		}
+		if (!lhstx) {
+			console.error('lhs textarea not defined - Mergely not initialized properly');
+			return;
+		}
+
 		// get current diff border color
 		var color = jQuery('<div style="display:none" class="mergely current start" />').appendTo('body').css('border-top-color');
 		this.current_diff_color = color;
 
 		// codemirror
-		var cmstyle = '#' + this.id + ' .CodeMirror-gutter-text { padding: 5px 0 0 0; }' +
-			'#' + this.id + ' .CodeMirror-lines pre, ' + '#' + this.id + ' .CodeMirror-gutter-text pre { line-height: 18px; }' +
-			'.CodeMirror-linewidget { overflow: hidden; };';
+		var cmstyle = `#${this.id} .CodeMirror-gutter-text { padding: 5px 0 0 0; }
+			'#${this.id} .CodeMirror-lines pre, #${this.id} .CodeMirror-gutter-text pre { line-height: 18px; }
+			'.CodeMirror-linewidget { overflow: hidden; };`;
 		if (this.settings.autoresize) {
-			cmstyle += this.id + ' .CodeMirror-scroll { height: 100%; overflow: auto; }';
+			cmstyle += `${this.id} .CodeMirror-scroll { height: 100%; overflow: auto; }`;
 		}
 		// adjust the margin line height
 		cmstyle += '\n.CodeMirror { line-height: 18px; }';
-		jQuery('<style type="text/css">' + cmstyle + '</style>').appendTo('head');
+		jQuery(`<style type="text/css">${cmstyle}</style>`).appendTo('head');
 
-		//bind
-		var rhstx = this.element.find('#' + this.id + '-rhs').get(0);
-		if (!rhstx) {
-			console.error('rhs textarea not defined - Mergely not initialized properly');
-			return;
-		}
-		var lhstx = this.element.find('#' + this.id + '-lhs').get(0);
-		if (!rhstx) {
-			console.error('lhs textarea not defined - Mergely not initialized properly');
-			return;
-		}
+		// bind
 		var self = this;
 		this.editor = [];
 		this.editor[this.id + '-lhs'] = CodeMirror.fromTextArea(lhstx, this.lhs_cmsettings);
@@ -1046,21 +1078,13 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 		}
 		return changes;
 	},
-	_get_viewport: function(editor_name1, editor_name2) {
-		var lhsvp = this.editor[editor_name1].getViewport();
-		var rhsvp = this.editor[editor_name2].getViewport();
-		return {from: Math.min(lhsvp.from, rhsvp.from), to: Math.max(lhsvp.to, rhsvp.to)};
+	_get_viewport_side: function(editor_name) {
+		return this.editor[editor_name].getViewport();
 	},
-	_is_change_in_view: function(vp, change) {
-		if (!this.settings.viewport) return true;
-		if ((change['lhs-line-from'] < vp.from && change['lhs-line-to'] < vp.to) ||
-			(change['lhs-line-from'] > vp.from && change['lhs-line-to'] > vp.to) ||
-			(change['rhs-line-from'] < vp.from && change['rhs-line-to'] < vp.to) ||
-			(change['rhs-line-from'] > vp.from && change['rhs-line-to'] > vp.to)) {
-			// if the change is outside the viewport, skip
-			return false;
-		}
-		return true;
+	_is_change_in_view: function(side, vp, change) {
+		return (change[`${side}-line-from`] >= vp.from && change[`${side}-line-from`] <= vp.to) ||
+			(change[`${side}-line-to`] >= vp.from && change[`${side}-line-to`] <= vp.to) ||
+			(vp.from >= change[`${side}-line-from`] && vp.to <= change[`${side}-line-to`]);
 	},
 	_set_top_offset: function (editor_name1) {
 		// save the current scroll position of the editor
@@ -1105,12 +1129,15 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 		}
 		var lhschc = this.editor[editor_name1].charCoords({line: 0});
 		var rhschc = this.editor[editor_name2].charCoords({line: 0});
-		var vp = this._get_viewport(editor_name1, editor_name2);
+		var lhsvp = this._get_viewport_side(editor_name1);
+		var rhsvp = this._get_viewport_side(editor_name2);
 
 		for (var i = 0; i < changes.length; ++i) {
 			var change = changes[i];
 
-			if (!this.settings.sidebar && !this._is_change_in_view(vp, change)) {
+			if (this.settings.viewport &&
+				!this._is_change_in_view(lhsvp, 'lhs', change) &&
+				!this._is_change_in_view(lhsvp, 'rhs', change)) {
 				// if the change is outside the viewport, skip
 				delete change['lhs-y-start'];
 				delete change['lhs-y-end'];
@@ -1205,11 +1232,18 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 		var led = this.editor[editor_name1];
 		var red = this.editor[editor_name2];
 		var current_diff = this._current_diff;
+		var lhsvp = this._get_viewport_side(editor_name1);
+		var rhsvp = this._get_viewport_side(editor_name2);
 
 		var timer = new Mgly.Timer();
 		led.operation(function() {
 			for (var i = 0; i < changes.length; ++i) {
 				var change = changes[i];
+				if (!this._is_change_in_view('lhs', lhsvp, change)) {
+					// if the change is outside the viewport, skip
+					continue;
+				}
+
 				var llf = change['lhs-line-from'] >= 0 ? change['lhs-line-from'] : 0;
 				var llt = change['lhs-line-to'] >= 0 ? change['lhs-line-to'] : 0;
 				var rlf = change['rhs-line-from'] >= 0 ? change['rhs-line-from'] : 0;
@@ -1252,24 +1286,22 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 					led.setGutterMarker(llf, 'merge', rhs_button.get(0));
 				}
 			}
-		});
-
-		var vp = this._get_viewport(editor_name1, editor_name2);
+		}.bind(this));
 
 		this.trace('change', 'markup lhs-editor time', timer.stop());
 		red.operation(function() {
 			for (var i = 0; i < changes.length; ++i) {
 				var change = changes[i];
+				if (!this._is_change_in_view('rhs', rhsvp, change)) {
+					// if the change is outside the viewport, skip
+					continue;
+				}
+
 				var llf = change['lhs-line-from'] >= 0 ? change['lhs-line-from'] : 0;
 				var llt = change['lhs-line-to'] >= 0 ? change['lhs-line-to'] : 0;
 				var rlf = change['rhs-line-from'] >= 0 ? change['rhs-line-from'] : 0;
 				var rlt = change['rhs-line-to'] >= 0 ? change['rhs-line-to'] : 0;
 
-				if (!self._is_change_in_view(vp, change)) {
-					// if the change is outside the viewport, skip
-					continue;
-				}
-
 				var clazz = ['mergely', 'rhs', change['op'], 'cid-' + i];
 				red.addLineClass(rlf, 'background', 'start');
 				red.addLineClass(rlt, 'background', 'end');
@@ -1307,7 +1339,7 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 					red.setGutterMarker(rlf, 'merge', lhs_button.get(0));
 				}
 			}
-		});
+		}.bind(this));
 		this.trace('change', 'markup rhs-editor time', timer.stop());
 
 		// mark text deleted, LCS changes
@@ -1319,17 +1351,17 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 			var rlf = change['rhs-line-from'] >= 0 ? change['rhs-line-from'] : 0;
 			var rlt = change['rhs-line-to'] >= 0 ? change['rhs-line-to'] : 0;
 
-			if (!this._is_change_in_view(vp, change)) {
-				// if the change is outside the viewport, skip
-				continue;
-			}
 			if (change['op'] == 'd') {
 				// apply delete to cross-out (left-hand side only)
 				var from = llf;
 				var to = llt;
-				var to_ln = led.lineInfo(to);
-				if (to_ln) {
-					marktext.push([led, {line:from, ch:0}, {line:to, ch:to_ln.text.length}, {className: 'mergely ch d lhs'}]);
+
+				if (this._is_change_in_view('lhs', lhsvp, change)) {
+					// the change is within the viewport
+					var to_ln = led.lineInfo(to);
+					if (to_ln) {
+						marktext.push([led, {line:from, ch:0}, {line:to, ch:to_ln.text.length}, {className: 'mergely ch d lhs'}]);
+					}
 				}
 			}
 			else if (change['op'] == 'c') {
@@ -1338,13 +1370,13 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 					 ((j >= 0) && (j <= llt)) || ((k >= 0) && (k <= rlt));
 					 ++j, ++k) {
 					var lhs_line, rhs_line;
-					if (k + p > rlt) {
+					if (k + p > rlt && this._is_change_in_view('lhs', lhsvp, change)) {
 						// lhs continues past rhs, mark lhs as deleted
 						lhs_line = led.getLine( j );
 						marktext.push([led, {line:j, ch:0}, {line:j, ch:lhs_line.length}, {className: 'mergely ch d lhs'}]);
 						continue;
 					}
-					if (j + p > llt) {
+					if (j + p > llt && this._is_change_in_view('rhs', rhsvp, change)) {
 						// rhs continues past lhs, mark rhs as added
 						rhs_line = red.getLine( k );
 						marktext.push([red, {line:k, ch:0}, {line:k, ch:rhs_line.length}, {className: 'mergely ch a rhs'}]);
@@ -1355,10 +1387,14 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 					var lcs = new Mgly.LCS(lhs_line, rhs_line);
 					lcs.diff(
 						function added (from, to) {
-							marktext.push([red, {line:k, ch:from}, {line:k, ch:to}, {className: 'mergely ch a rhs'}]);
+							if (self._is_change_in_view('rhs', rhsvp, change)) {
+								marktext.push([red, {line:k, ch:from}, {line:k, ch:to}, {className: 'mergely ch a rhs'}]);
+							}
 						},
 						function removed (from, to) {
-							marktext.push([led, {line:j, ch:from}, {line:j, ch:to}, {className: 'mergely ch d lhs'}]);
+							if (self._is_change_in_view('lhs', lhsvp, change)) {
+								marktext.push([led, {line:j, ch:from}, {line:j, ch:to}, {className: 'mergely ch d lhs'}]);
+							}
 						}
 					);
 				}
@@ -1413,29 +1449,37 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 			return false;
 		});
 
-		// gutter markup
-		var lhsLineNumbers = jQuery('#mergely-lhs ~ .CodeMirror').find('.CodeMirror-linenumber');
-		var rhsLineNumbers = jQuery('#mergely-rhs ~ .CodeMirror').find('.CodeMirror-linenumber');
+		// gutter markup that highlights all gutter line numbers for the current change.
+		// cm doesn't give us the ability to style the line numbers directly.
+		var lhsLineNumbers = jQuery('#mergely-lhs ~ .CodeMirror .CodeMirror-code .CodeMirror-linenumber.CodeMirror-gutter-elt');
+		var rhsLineNumbers = jQuery('#mergely-rhs ~ .CodeMirror .CodeMirror-code .CodeMirror-linenumber.CodeMirror-gutter-elt');
+		var jf, jt, i, j;
 		rhsLineNumbers.removeClass('mergely current');
 		lhsLineNumbers.removeClass('mergely current');
-		for (var i = 0; i < changes.length; ++i) {
-			if (current_diff == i && change.op !== 'd') {
-				var change = changes[i];
-				var j, jf = change['rhs-line-from'], jt = change['rhs-line-to'] + 1;
-				for (j = jf; j < jt; j++) {
-					var n = (j + 1).toString();
-					rhsLineNumbers
-						.filter(function(i, node) { return jQuery(node).text() === n; })
-					.addClass('mergely current');
+		var lhsvpFrom = parseInt(lhsLineNumbers.eq(0).text(), 10) - 1;
+		var lhsvpTo = parseInt(lhsLineNumbers.eq(lhsLineNumbers.length - 1).text(), 10);
+		var rhsvpFrom = parseInt(rhsLineNumbers.eq(0).text(), 10) - 1;
+		var rhsvpTo = parseInt(rhsLineNumbers.eq(rhsLineNumbers.length - 1).text(), 10);
+
+		for (i = 0; i < changes.length; ++i) {
+			change = changes[i];
+
+			if (current_diff == i && change.op !== 'a') {
+				jf = change['lhs-line-from']
+				jt = change['lhs-line-to'] + 1;
+				for (j = jf; j < jt; ++j) {
+					if (j >= lhsvpFrom && j <= lhsvpTo) {
+						lhsLineNumbers.eq(j - lhsvpFrom).addClass('mergely current');
+					}
 				}
 			}
-			if (current_diff == i && change.op !== 'a') {
-				var change = changes[i];
-				jf = change['lhs-line-from'], jt = change['lhs-line-to'] + 1;
-				for (j = jf; j < jt; j++) {
-					var n = (j + 1).toString();
-					lhsLineNumbers.filter(function(i, node) { return jQuery(node).text() === n; })
-					.addClass('mergely current');
+			if (current_diff == i && change.op !== 'd') {
+				jf = change['rhs-line-from']
+				jt = change['rhs-line-to'] + 1;
+				for (j = jf; j < jt; ++j) {
+					if (j >= rhsvpFrom && j <= rhsvpTo) {
+						rhsLineNumbers.eq(j - rhsvpFrom).addClass('mergely current');
+					}
 				}
 			}
 		}
@@ -1538,7 +1582,9 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 		ctx_rhs.fillRect(0, 0, 6.5, ex.visible_page_height);
 		ctx_rhs.strokeRect(0, 0, 6.5, ex.visible_page_height);
 
-		var vp = this._get_viewport(editor_name1, editor_name2);
+		var lhsvp = this._get_viewport_side(editor_name1);
+		var rhsvp = this._get_viewport_side(editor_name2);
+
 		for (var i = 0; i < changes.length; ++i) {
 			var change = changes[i];
 			var fill = this.settings.fgcolor[change['op']];
@@ -1568,7 +1614,9 @@ jQuery.extend(Mgly.CodeMirrorDiffView.prototype, {
 			ctx_rhs.fillRect(1.5, rhs_y_start, 4.5, Math.max(rhs_y_end - rhs_y_start, 5));
 			ctx_rhs.strokeRect(1.5, rhs_y_start, 4.5, Math.max(rhs_y_end - rhs_y_start, 5));
 
-			if (!this._is_change_in_view(vp, change)) {
+			if (!this._is_change_in_view('lhs', lhsvp, change) &&
+				!this._is_change_in_view('rhs', rhsvp, change)) {
+				// if the change is outside the viewport, skip
 				continue;
 			}
 

tests/mergely.spec.js

@@ -1,6 +1,7 @@
 const jQuery = require('jquery');
 const CodeMirror = require('CodeMirror');
 const mergely = require('../src/mergely');
+const macbeth = require('./data/macbeth').join('\n');
 const $ = jQuery;
 
 (function($) {
@@ -19,9 +20,10 @@ describe('mergely', function () {
 	};
 
 	afterEach(() => {
-		$('#mergely').mergely('unbind');
-		$('#mergely').mergelyUnregister();
-		$('#mergely').remove();
+		const mergely = $('#mergely');
+		mergely.mergely('unbind');
+		mergely.mergelyUnregister();
+		mergely.remove();
 	});
 
 	describe('initialization', () => {
@@ -400,6 +402,7 @@ describe('mergely', function () {
 						for (let i = 0; i < opt.next; ++i) {
 							$('#mergely').mergely('scrollToDiff', 'next');
 						}
+						expect($('.merge-button').length > 0).to.be.true;
 						$('#mergely').mergely('mergeCurrentChange', opt.dir);
 						if (opt.dir === 'lhs') {
 							expect($('#mergely').mergely('get', 'lhs')).to.equal(opt.expect || opt.rhs);
@@ -414,4 +417,139 @@ describe('mergely', function () {
 			});
 		});
 	});
+
+	describe('_is_change_in_view', () => {
+		it('should be false when change less-than viewport', function (done) {
+			$(document).ready(() => {
+				const editor = init({
+					height: 100,
+					viewport: true,
+					license: 'lgpl-separate-notice',
+					lhs: (setValue) => setValue(macbeth),
+					rhs: (setValue) => setValue(macbeth)
+				});
+				const { mergely } = $('#mergely');
+				expect($('#mergely').mergely('_is_change_in_view', 'lhs', {from: 10, to: 20}, {
+					'lhs-line-from': 0,
+					'lhs-line-to': 9
+				})).to.be.false;
+				done();
+			});
+		});
+
+		it('should be true when change less-than-equal viewport', function (done) {
+			$(document).ready(() => {
+				const editor = init({
+					height: 100,
+					viewport: true,
+					license: 'lgpl-separate-notice',
+					lhs: (setValue) => setValue(macbeth),
+					rhs: (setValue) => setValue(macbeth)
+				});
+				const { mergely } = $('#mergely');
+				expect($('#mergely').mergely('_is_change_in_view', 'lhs', {from: 10, to: 20}, {
+					'lhs-line-from': 0,
+					'lhs-line-to': 10
+				})).to.be.true;
+				done();
+			});
+		});
+
+		it('should be false when change greater-than viewport', function (done) {
+			$(document).ready(() => {
+				const editor = init({
+					height: 100,
+					viewport: true,
+					license: 'lgpl-separate-notice',
+					lhs: (setValue) => setValue(macbeth),
+					rhs: (setValue) => setValue(macbeth)
+				});
+				const { mergely } = $('#mergely');
+				expect($('#mergely').mergely('_is_change_in_view', 'lhs', {from: 10, to: 20}, {
+					'lhs-line-from': 21,
+					'lhs-line-to': 22
+				})).to.be.false;
+				done();
+			});
+		});
+
+		it('should be true when change straddles viewport from', function (done) {
+			$(document).ready(() => {
+				const editor = init({
+					height: 100,
+					viewport: true,
+					license: 'lgpl-separate-notice',
+					lhs: (setValue) => setValue(macbeth),
+					rhs: (setValue) => setValue(macbeth)
+				});
+				const { mergely } = $('#mergely');
+				expect($('#mergely').mergely('_is_change_in_view', 'lhs', {from: 10, to: 20}, {
+					'lhs-line-from': 5,
+					'lhs-line-to': 11
+				})).to.be.true;
+				done();
+			});
+		});
+
+		it('should be true when change straddles viewport to', function (done) {
+			$(document).ready(() => {
+				const editor = init({
+					height: 100,
+					viewport: true,
+					license: 'lgpl-separate-notice',
+					lhs: (setValue) => setValue(macbeth),
+					rhs: (setValue) => setValue(macbeth)
+				});
+				const { mergely } = $('#mergely');
+				expect($('#mergely').mergely('_is_change_in_view', 'lhs', {from: 10, to: 20}, {
+					'lhs-line-from': 15,
+					'lhs-line-to': 21
+				})).to.be.true;
+				done();
+			});
+		});
+
+		it('should be true when change encompasses viewport', function (done) {
+			$(document).ready(() => {
+				const editor = init({
+					height: 100,
+					viewport: true,
+					license: 'lgpl-separate-notice',
+					lhs: (setValue) => setValue(macbeth),
+					rhs: (setValue) => setValue(macbeth)
+				});
+				const { mergely } = $('#mergely');
+				expect($('#mergely').mergely('_is_change_in_view', 'lhs', {from: 10, to: 20}, {
+					'lhs-line-from': 0,
+					'lhs-line-to': 25
+				})).to.be.true;
+				done();
+			});
+		});
+
+		it('should not be vulnerable to XSS', function (done) {
+			function initXSS(options) {
+				$('body').get(0).innerHTML = "<!DOCTYPE html><html lang=\"en\"><body><div id='mergely<script id=\"injected\">alert(123)</script>'></div></body></html>";
+				const divs = document.getElementsByTagName('div');
+				editor = $(divs[0]);
+				editor.mergely(options);
+				return editor;
+			};
+
+			$(document).ready(() => {
+				const editor = initXSS({
+					height: 100,
+					viewport: true,
+					license: 'lgpl-separate-notice',
+					lhs: (setValue) => setValue(macbeth),
+					rhs: (setValue) => setValue(macbeth)
+				});
+				expect($('body').find('#injected')).to.have.length(0, 'expected no div with id injected');
+				const divs = document.getElementsByTagName('div');
+				expect(divs).to.have.length(1);
+				expect(divs[0].id).to.equal('mergely<script id="injected">alert(123)</script>');
+				done();
+			});
+		});
+	});
 });