Loosely couple Node.js code to canvas module.

Treat absence of canvas module like a web worker context.
Relates to #1103

gulp/tasks/build.js

@@ -47,7 +47,7 @@ buildNames.forEach(function(name) {
                 evaluate: ['src/constants.js'],
                 setup: function() {
                     // Return objects to be defined in the preprocess-scope.
-                    // Note that this would be merge in with already existing
+                    // Note that this would be merged in with already existing
                     // objects.
                     return {
                         __options: Object.assign({}, options, buildOptions[name])

src/core/PaperScript.js

@@ -347,7 +347,7 @@ Base.exports.PaperScript = function() {
             }
             if (/^(inline|both)$/.test(sourceMaps)) {
                 code += "\n//# sourceMappingURL=data:application/json;base64,"
-                        + window.btoa(unescape(encodeURIComponent(
+                        + self.btoa(unescape(encodeURIComponent(
                             JSON.stringify(map))));
             }
             code += "\n//# sourceURL=" + (url || 'paperscript');

src/export.js

@@ -36,7 +36,7 @@ paper = new (PaperScope.inject(Base.exports, {
 // - PaperScript support in require() with sourceMaps
 // - exportFrames / exportImage on CanvasView
 if (paper.agent.node)
-    require('./node/extend')(paper);
+    require('./node/extend.js')(paper);
 
 // https://github.com/umdjs/umd
 if (typeof define === 'function' && define.amd) {

src/init.js

@@ -19,11 +19,12 @@
 /* global document:true, window:true */
 // Create a window variable valid in the paper.js scope, that points to the
 // native window in browsers and the emulated JSDom one in node.js
-// In workers, window is null (but self is defined), so we can use the validity
-// of the local window object to detect a worker-like context in the library.
-var window = self ? self.window : require('./node/window'),
-    document = window && window.document;
-// Make sure 'self' always points to a window object, also on Node.js.
+// In workers, and on Node.js when no Canvas is present, `window` is null (but
+// `self` is defined), so we can use the validity of the local window object to
+// detect a worker-like context in the library.
+// Make sure `self` always points to a window object, also on Node.js.
+self = self || require('./node/window.js');
 // NOTE: We're not modifying the global `self` here. We receive its value passed
 // to the paper.js function scope, and this is the one that is modified here.
-self = self || window;
+var window = self.window,
+    document = self.document;

src/item/Raster.js

@@ -379,7 +379,7 @@ var Raster = Item.extend(/** @lends Raster# */{
     },
 
     setSource: function(src) {
-        var image = new window.Image(),
+        var image = new self.Image(),
             crossOrigin = this._crossOrigin;
         if (crossOrigin)
             image.crossOrigin = crossOrigin;

src/net/Http.js

@@ -13,7 +13,7 @@
 var Http = {
     request: function(options) {
         // Code borrowed from Coffee Script and extended:
-        var xhr = new window.XMLHttpRequest();
+        var xhr = new self.XMLHttpRequest();
         xhr.open((options.method || 'get').toUpperCase(), options.url,
                 Base.pick(options.async, true));
         if (options.mimeType)

src/node/canvas.js

@@ -10,16 +10,29 @@
  * All rights reserved.
  */
 
-var Canvas = require('canvas'),
-    idlUtils = require('jsdom/lib/jsdom/living/generated/utils');
-
 // Add some useful extensions to HTMLCanvasElement:
 // - HTMLCanvasElement#type, so we can switch to a PDF canvas
 // - Various Node Canvas methods, routed through from HTMLCanvasElement:
 //   toBuffer, pngStream, createPNGStream, jpgStream, createJPGStream
 
 module.exports = function(window) {
-    var HTMLCanvasElement = window.HTMLCanvasElement;
+    var Canvas;
+    try {
+        Canvas = require('canvas');
+    } catch(e) {
+        // Remove `self.window`, so we still have the global `self` reference,
+        // but no `window` object:
+        // - On the browser, this corresponds to a worker context.
+        // - On Node.js, it basically means the canvas is missing or not working
+        //   which can be treated the same way.
+        delete window.window;
+        console.info(
+                'Unable to load Canvas module. Running in a headless context.');
+        return;
+    }
+
+    var idlUtils = require('jsdom/lib/jsdom/living/generated/utils'),
+        HTMLCanvasElement = window.HTMLCanvasElement;
 
     // Add fake HTMLCanvasElement#type property:
     Object.defineProperty(HTMLCanvasElement.prototype, 'type', {

src/node/window.js

@@ -27,7 +27,7 @@ var document = jsdom.jsdom('<html><body></body></html>', {
     }),
     window = document.defaultView;
 
-require('./canvas')(window);
+require('./canvas.js')(window);
 
 // Define XMLSerializer and DOMParser shims, to emulate browser behavior.
 // Effort to bring this to jsdom: https://github.com/tmpvar/jsdom/issues/1368

src/svg/SvgExport.js

@@ -369,7 +369,7 @@ new function() {
             definitions = null;
         }
         return options.asString
-                ? new window.XMLSerializer().serializeToString(svg)
+                ? new self.XMLSerializer().serializeToString(svg)
                 : svg;
     }
 

src/svg/SvgImport.js

@@ -553,10 +553,12 @@ new function() {
         // WebKit. We also get variations of quotes or no quotes, single or
         // double, so handle it all with one regular expression:
         var match = value && value.match(/\((?:["'#]*)([^"')]+)/),
-            res = match && definitions[match[1]
-                // This is required by Firefox, which can produce absolute urls
-                // for local gradients, see #1001:
-                .replace(window.location.href.split('#')[0] + '#', '')];
+            name = match && match[1],
+            res = name && definitions[window
+                    // This is required by Firefox, which can produce absolute
+                    // urls for local gradients, see #1001:
+                    ? name.replace(window.location.href.split('#')[0] + '#', '')
+                    : name];
         // Patch in support for SVG's gradientUnits="objectBoundingBox" through
         // Color#_scaleToBounds
         if (res && res._scaleToBounds) {
@@ -659,7 +661,7 @@ new function() {
 
         function onLoad(svg) {
             try {
-                var node = typeof svg === 'object' ? svg : new window.DOMParser()
+                var node = typeof svg === 'object' ? svg : new self.DOMParser()
                         .parseFromString(svg, 'image/svg+xml');
                 if (!node.nodeName) {
                     node = null;

test/helpers.js

@@ -86,7 +86,7 @@ var equals = function(actual, expected, message, options) {
             || type === 'boolean' && 'Boolean'
             || type === 'undefined' && 'Undefined'
             || Array.isArray(expected) && 'Array'
-            || expected instanceof window.Element && 'Element' // handle DOM Elements
+            || expected instanceof self.Element && 'Element' // handle DOM Elements
             || (cls = expected && expected._class) // check _class 2nd last
             || type === 'object' && 'Object'; // Object as catch-all
     var comparator = type && comparators[type];