diff --git a/src/context2ddrawer.js b/src/context2ddrawer.js
index b07d9411..4516856c 100644
--- a/src/context2ddrawer.js
+++ b/src/context2ddrawer.js
@@ -81,7 +81,7 @@ class Context2dDrawer extends $.DrawerBase{
     /**
      * @returns {Boolean} true if canvas is supported by the browser, otherwise false
      */
-    isSupported(){
+    static isSupported(){
         return $.supportsCanvas;
     }
 
diff --git a/src/drawerbase.js b/src/drawerbase.js
index 93dbcf1b..245e6939 100644
--- a/src/drawerbase.js
+++ b/src/drawerbase.js
@@ -76,11 +76,6 @@ $.DrawerBase = class DrawerBase{
         this.debugGridColor = typeof options.debugGridColor === 'string' ? [options.debugGridColor] : options.debugGridColor || $.DEFAULT_SETTINGS.debugGridColor;
         this.options = options.options || {};
 
-        // TO DO: This was deprectated previously. Can we get rid of it at this point?
-        if (options.opacity) {
-            $.console.error( "[Drawer] options.opacity is no longer accepted; set the opacity on the TiledImage instead" );
-        }
-
         /**
          * The parent element of this Drawer instance, passed in when the Drawer was created.
          * The parent of {@link OpenSeadragon.DrawerBase#canvas}.
@@ -130,7 +125,7 @@ $.DrawerBase = class DrawerBase{
     /**
      * @returns {Boolean} whether the drawer implementation is supported by the browser
      */
-    isSupported() {
+    static isSupported() {
         $.console.error('Drawer.isSupported must be implemented by child class');
     }
 
@@ -221,7 +216,7 @@ $.DrawerBase = class DrawerBase{
         /**
          * This event is fired just before the tile is drawn giving the application a chance to alter the image.
          *
-         * NOTE: This event is only fired in certain drawing contexts: either the 'context2d' drawer is
+         * NOTE: This event is only fired in certain drawing contexts: either the 'canvas' drawer is
          * being used, or the 'webgl' drawer with 'drawerOptions.webgl.continuousTileRefresh'.
          *
          * @event tile-drawing
diff --git a/src/htmldrawer.js b/src/htmldrawer.js
index 1b3306fa..20117b40 100644
--- a/src/htmldrawer.js
+++ b/src/htmldrawer.js
@@ -61,7 +61,7 @@ class HTMLDrawer extends $.DrawerBase{
     /**
      * @returns {Boolean} always true
      */
-    isSupported(){
+    static isSupported(){
         return true;
     }
 
diff --git a/src/imagetilesource.js b/src/imagetilesource.js
index 4596b2c0..b039cc2b 100644
--- a/src/imagetilesource.js
+++ b/src/imagetilesource.js
@@ -195,6 +195,8 @@
         /**
          * Destroys ImageTileSource
          * @function
+         * @param {OpenSeadragon.Viewer} viewer the viewer that is calling
+         * destroy on the ImageTileSource
          */
         destroy: function (viewer) {
             this._freeupCanvasMemory(viewer);
@@ -273,17 +275,20 @@
                     this.levels[i].context2D.canvas.height = 0;
                     this.levels[i].context2D.canvas.width = 0;
 
-                    /**
-                     * Triggered when an image has just been unloaded
-                     *
-                     * @event image-unloaded
-                     * @memberof OpenSeadragon.Viewer
-                     * @type {object}
-                     * @property {CanvasRenderingContext2D} context2D - The context that is being unloaded
-                     */
-                    viewer.raiseEvent("image-unloaded", {
-                        context2D: this.levels[i].context2D
-                    });
+                    if(viewer){
+                        /**
+                        * Triggered when an image has just been unloaded
+                        *
+                        * @event image-unloaded
+                        * @memberof OpenSeadragon.Viewer
+                        * @type {object}
+                        * @property {CanvasRenderingContext2D} context2D - The context that is being unloaded
+                        */
+                        viewer.raiseEvent("image-unloaded", {
+                            context2D: this.levels[i].context2D
+                        });
+                    }
+
                 }
             }
         },
diff --git a/src/openseadragon.js b/src/openseadragon.js
index 1e6f1d75..cfa80df5 100644
--- a/src/openseadragon.js
+++ b/src/openseadragon.js
@@ -190,8 +190,8 @@
   *     Zoom level to use when image is first opened or the home button is clicked.
   *     If 0, adjusts to fit viewer.
   *
-  * @property {String|DrawerImplementation|Array} [drawer = ['webgl', 'context2d', 'html']]
-  *     Which drawer to use. Valid strings are 'context2d' and 'html'. Valid drawer
+  * @property {String|DrawerImplementation|Array} [drawer = ['webgl', 'canvas', 'html']]
+  *     Which drawer to use. Valid strings are 'webgl', 'canvas', and 'html'. Valid drawer
   *     implementations are constructors of classes that extend OpenSeadragon.DrawerBase.
   *     An array of strings and/or constructors can be used to indicate the priority
   *     of different implementations, which will be tried in order based on browser support.
@@ -1346,8 +1346,7 @@ function OpenSeadragon( options ){
             compositeOperation:                null, // to be passed into each TiledImage
 
             // DRAWER SETTINGS
-            drawer:                            ['webgl', 'context2d', 'html'], // prefer using webgl, context2d, fallback to html
-            useCanvas:                         true,  // deprecated - set drawer and drawerOptions
+            drawer:                            ['webgl', 'canvas', 'html'], // prefer using webgl, context2d, fallback to html
                 /**
                  * drawerOptions dictionary.
                  * @type {Object} drawerOptions
diff --git a/src/tilesource.js b/src/tilesource.js
index ea861919..4961a47f 100644
--- a/src/tilesource.js
+++ b/src/tilesource.js
@@ -423,41 +423,6 @@ $.TileSource.prototype = {
         return new $.Rect( px * scale, py * scale, sx * scale, sy * scale );
     },
 
-    /**
-     * @function
-     * @param {Number} level
-     * @param {Number} x
-     * @param {Number} y
-     * @param {Boolean} [isSource=false] Whether to return the source bounds of the tile.
-     * @returns {OpenSeadragon.Rect} Either where this tile fits (in normalized coordinates unless imageCoordinates == true) or the
-     * portion of the tile to use as the source of the drawing operation (in pixels), depending on
-     * the isSource parameter, without overlap.
-     */
-    getTileBoundsNoOverlap: function( level, x, y, isSource, imageCoordinates ) {
-        var dimensionsScaled = this.dimensions.times( this.getLevelScale( level ) ),
-            tileWidth = this.getTileWidth(level),
-            tileHeight = this.getTileHeight(level),
-            tileOverlap = this.tileOverlap || 0,
-            px = tileWidth * x,
-            py = tileHeight * y,
-            sx = tileWidth,
-            sy = tileHeight,
-            scale = 1.0 / dimensionsScaled.x;
-
-        sx = Math.min( sx, dimensionsScaled.x - px );
-        sy = Math.min( sy, dimensionsScaled.y - py );
-
-        if (isSource) {
-            return new $.Rect((x === 0 ? 0 : tileOverlap), (y === 0 ? 0 : tileOverlap), sx, sy);
-        } else if ( imageCoordinates ){
-            return new $.Rect( px, py, sx, sy).times(scale * this.width);
-        } else {
-            return new $.Rect( px, py, sx, sy).times(scale);
-        }
-
-
-    },
-
 
     /**
      * Responsible for retrieving, and caching the
diff --git a/src/viewer.js b/src/viewer.js
index bcb7cc94..f39e6251 100644
--- a/src/viewer.js
+++ b/src/viewer.js
@@ -446,7 +446,7 @@ $.Viewer = function( options ) {
         delete this.drawerOptions.useCanvas;
     }
     let drawerPriority = Array.isArray(this.drawer) ? this.drawer : [this.drawer];
-    let drawersToTry = drawerPriority.filter(d => ['webgl', 'context2d', 'html'].includes(d) || (d.prototype && d.prototype.isOpenSeadragonDrawer) );
+    let drawersToTry = drawerPriority.filter(d => ['webgl', 'canvas', 'html'].includes(d) || (d.prototype && d.prototype.isOpenSeadragonDrawer) );
     if(drawerPriority.length !== drawersToTry.length){
         $.console.error('An invalid drawer was requested.');
     }
@@ -460,9 +460,9 @@ $.Viewer = function( options ) {
         let Drawer = drawersToTry[i];
         let optsKey = null;
         // replace text-based option with appropriate constructor
-        if (Drawer === 'context2d'){
+        if (Drawer === 'canvas'){
             Drawer = $.Context2dDrawer;
-            optsKey = 'context2d';
+            optsKey = 'canvas';
         } else if (Drawer === 'html'){
             Drawer = $.HTMLDrawer;
             optsKey = 'html';
@@ -473,7 +473,7 @@ $.Viewer = function( options ) {
             optsKey = 'custom';
         }
         // if the drawer is supported, create it and break the loop
-        if (Drawer.prototype.isSupported()){
+        if (Drawer.isSupported()){
             this.drawer = new Drawer({
                 viewer:             this,
                 viewport:           this.viewport,
diff --git a/src/webgldrawer.js b/src/webgldrawer.js
index e61ac8fd..5b98f56b 100644
--- a/src/webgldrawer.js
+++ b/src/webgldrawer.js
@@ -234,10 +234,10 @@
         // Public API required by all Drawer implementations
 
         /**
-            * @returns {Boolean} returns true if canvas and webgl are supported and
-            * three.js has been exposed as a global variable named THREE
-            */
-        isSupported(){
+        * @returns {Boolean} returns true if canvas and webgl are supported and
+        * three.js has been exposed as a global variable named THREE
+        */
+        static isSupported(){
             let canvasElement = document.createElement( 'canvas' );
             let webglContext = $.isFunction( canvasElement.getContext ) &&
                         canvasElement.getContext( 'webgl' );
diff --git a/src/world.js b/src/world.js
index 30e9fc48..fa459317 100644
--- a/src/world.js
+++ b/src/world.js
@@ -242,6 +242,9 @@ $.extend( $.World.prototype, $.EventSource.prototype, /** @lends OpenSeadragon.W
 
     /**
      * Updates (i.e. animates bounds of) all items.
+     * @function
+     * @param viewportChanged Whether the viewport changed, which indicates that
+     * all TiledImages need to be updated.
      */
     update: function(viewportChanged) {
         var animated = false;
diff --git a/test/demo/collections/main.js b/test/demo/collections/main.js
index b5cf86ca..0806bedc 100644
--- a/test/demo/collections/main.js
+++ b/test/demo/collections/main.js
@@ -16,7 +16,7 @@
                 // debugMode: true,
                 zoomPerScroll: 1.02,
                 showNavigator: testNavigator,
-                drawer: ['context2d', 'html'],
+                drawer: ['canvas', 'html'],
                 // defaultZoomLevel: 2,
                 // homeFillsViewer: true,
                 // sequenceMode: true,
diff --git a/test/demo/drawercomparison.html b/test/demo/drawercomparison.html
index ad82b6f6..99c2b946 100644
--- a/test/demo/drawercomparison.html
+++ b/test/demo/drawercomparison.html
@@ -65,7 +65,7 @@
         <div class="mirrored">
             <div>
                 <h3>Context2d drawer (default in OSD &lt;= 4.1.0)</h3>
-                <div id="context2d" class="viewer-container"></div>
+                <div id="canvasdrawer" class="viewer-container"></div>
             </div>
 
             <div>
diff --git a/test/demo/drawercomparison.js b/test/demo/drawercomparison.js
index 2199c2b6..7edb0101 100644
--- a/test/demo/drawercomparison.js
+++ b/test/demo/drawercomparison.js
@@ -15,9 +15,9 @@ const labels = {
 }
 
 //Double viewer setup for comparison - Context2dDrawer and WebGLDrawer
-// viewer1: context2d drawer
+// viewer1: canvas drawer
 let viewer1 = window.viewer1 = OpenSeadragon({
-    id: "context2d",
+    id: "canvasdrawer",
     prefixUrl: "../../build/openseadragon/images/",
     minZoomImageRatio:0.01,
     maxZoomPixelRatio:100,
@@ -25,7 +25,7 @@ let viewer1 = window.viewer1 = OpenSeadragon({
     crossOriginPolicy: 'Anonymous',
     ajaxWithCredentials: false,
     // maxImageCacheCount: 30,
-    drawer:'context2d',
+    drawer:'canvas',
     blendTime:0
 });
 
diff --git a/test/demo/webgldemodrawer.js b/test/demo/webgldemodrawer.js
index 41346f7a..61e7c13c 100644
--- a/test/demo/webgldemodrawer.js
+++ b/test/demo/webgldemodrawer.js
@@ -238,10 +238,10 @@
         // Public API required by all Drawer implementations
 
         /**
-            * @returns {Boolean} returns true if canvas and webgl are supported and
-            * three.js has been exposed as a global variable named THREE
-            */
-        isSupported(){
+        * @returns {Boolean} returns true if canvas and webgl are supported and
+        * three.js has been exposed as a global variable named THREE
+        */
+        static isSupported(){
             let canvasElement = document.createElement( 'canvas' );
             let webglContext = $.isFunction( canvasElement.getContext ) &&
                         canvasElement.getContext( 'webgl' );
diff --git a/test/modules/drawer.js b/test/modules/drawer.js
index e4f507a3..ad953080 100644
--- a/test/modules/drawer.js
+++ b/test/modules/drawer.js
@@ -45,7 +45,7 @@
         var done = assert.async();
         createViewer({
             tileSources: '/test/data/testpattern.dzi',
-            drawer: 'context2d', // this test only makes sense for certain drawers
+            drawer: 'canvas', // this test only makes sense for certain drawers
         });
 
         viewer.addHandler('open', function handler(event) {
@@ -76,7 +76,7 @@
         var done = assert.async();
         createViewer({
             tileSources: '/test/data/testpattern.dzi',
-            drawer: 'context2d' // test only makes sense for this drawer
+            drawer: 'canvas' // test only makes sense for this drawer
         });
         var drawer = viewer.drawer;
 
diff --git a/test/modules/navigator.js b/test/modules/navigator.js
index 1523fa63..ab1be8d3 100644
--- a/test/modules/navigator.js
+++ b/test/modules/navigator.js
@@ -45,9 +45,9 @@
             // if ( viewer && viewer.close ) {
             //     viewer.close();
             // }
-            // if (viewer && viewer.destroy){
-            //     viewer.destroy();
-            // }
+            if (viewer && viewer.destroy){
+                viewer.destroy();
+            }
 
             viewer = null;
         }
diff --git a/test/modules/tiledimage.js b/test/modules/tiledimage.js
index e9675356..123ff890 100644
--- a/test/modules/tiledimage.js
+++ b/test/modules/tiledimage.js
@@ -135,7 +135,7 @@
     QUnit.test('update', function(assert) {
         var done = assert.async();
         var handlerCount = 0;
-        var testTileDrawingEvent = viewer.drawerOptions.type === 'context2d';
+        var testTileDrawingEvent = viewer.drawerOptions.type === 'canvas';
         let expectedHandlers = testTileDrawingEvent ? 4 : 3;
 
         viewer.addHandler('open', function(event) {