Use canvas-prebuilt instead of canvas in order to drop external dependencies

.travis.yml

@@ -1,24 +1,10 @@
-sudo: required
-services:
-  - docker
 language: node_js
 node_js:
   - '8'
   - '9'
 cache:
   directories:
     - node_modules
-addons:
-  apt:
-    packages:
-      - gcc-4.8
-      - g++-4.8
-      - libcairo2-dev
-      - libjpeg8-dev
-      - libgif-dev
-      - libpango1.0-dev
-
-env: CXX="g++-4.8" CC="gcc-4.8"
 
 script: "npm run-script travis"
 after_success: "<coverage/lcov.info ./node_modules/coveralls/bin/coveralls.js"

README.md

@@ -160,19 +160,6 @@ Color Module</a>, as far as I can tell. Defaults to `transparent`.
 Installation
 ------------
 
-For creating the sprite images themselves AssetGraph-sprite uses <a
-href="http://github.com/LearnBoost/node-canvas">node-canvas</a>, which
-is not a pure-node module and requires the Cairo development sources
-(version 1.10 or later), `libjpeg` (version 8 or later) and
-`libgif`. On Ubuntu 10.10 and above you should be able to get them
-like this:
-
-```
-$ sudo apt-get install libcairo2-dev libgif-dev libjpeg8-dev
-```
-
-Now you can proceed to install AssetGraph-sprite:
-
 ```
 $ npm install assetgraph-sprite
 ```

lib/spriteBackgroundImages.js

@@ -1,11 +1,10 @@
 const queryString = require('querystring');
 const { promisify } = require('util');
 const packers = require('./packers');
-let Canvas;
+const canvasPrebuilt = require('canvas-prebuilt');
 
-try {
-    Canvas = require('canvas');
-} catch (e) {}
+const Canvas = canvasPrebuilt.Canvas;
+const Image = canvasPrebuilt.Image;
 
 // Helper for extracting all nodes defining a specific property from a postcss rule
 function getProperties(container, propertyName) {
@@ -15,10 +14,14 @@ function getProperties(container, propertyName) {
 }
 
 async function getCanvasImageFromImageAsset(imageAsset) {
-    const canvasImage = new Canvas.Image();
+    const canvasImage = new Image();
     await new Promise((resolve, reject) => {
         canvasImage.onerror = err => {
-            err.message += ' (' + imageAsset.urlOrDescription + ')';
+            if (err.message.includes('node-canvas was built without SVG support')) {
+                err.message = 'Adding SVG images to a sprite is not possible';
+            }
+
+            err.message += ` (${imageAsset.urlOrDescription})`;
             reject(err);
         };
         canvasImage.onload = resolve;
@@ -107,20 +110,6 @@ function extractInfoFromCssRule(cssRule, propertyNamePrefix) {
 
 module.exports = () => {
     return async function spriteBackgroundImages(assetGraph) {
-        if (!Canvas) {
-            assetGraph.warn(new Error('assetgraph-sprite: Canvas not found, skipping'));
-            return;
-        }
-
-        // Waiting for https://github.com/LearnBoost/node-canvas/issues/52
-        const cairoVersion = Canvas.cairoVersion.split('.').map(
-            str => parseInt(str, 10)
-        );
-        if (cairoVersion[0] < 1 || cairoVersion[1] < 10) {
-            assetGraph.warn(new Error('assetgraph-sprite: Cannot create sprites due to missing canvas.getContext("2d").drawImage() support. Please compile node-canvas with Cairo version 1.10.0 or above.'));
-            return;
-        }
-
         const spriteGroups = {};
 
         // Find sprite annotated images and create a data structure with their information

package.json

@@ -16,9 +16,6 @@
   "files": [
     "lib"
   ],
-  "optionalDependencies": {
-    "canvas": "1.6.5"
-  },
   "devDependencies": {
     "assetgraph": "5.4.0",
     "coveralls": "^3.0.0",
@@ -39,5 +36,8 @@
     "coverage": "istanbul cover _mocha",
     "travis": "npm run lint && npm run coverage"
   },
-  "main": "lib/spriteBackgroundImages.js"
+  "main": "lib/spriteBackgroundImages.js",
+  "dependencies": {
+    "canvas-prebuilt": "2.0.0-alpha.14"
+  }
 }

test/spriteBackgroundImages.js

@@ -345,6 +345,6 @@ describe('spriteBackgroundImages', function () {
 
         expect(assetGraph, 'to contain asset', 'Svg');
 
-        await expect(assetGraph.queue(spriteBackgroundImages()), 'to be rejected with', /error while reading from input stream/);
+        await expect(assetGraph.queue(spriteBackgroundImages()), 'to be rejected with', /Adding SVG images to a sprite is not possible/);
     });
 });