Screen snippet (#55)

* adds screen snippet feature

* update return api

* udpate unit tests

demo/index.html

@@ -40,6 +40,12 @@
         <button id='inc-badge'>increment badge count</button>
         <br>
         <button id='clear-badge'>clear badge count</button>
+        <br>
+        <hr>
+        <p>Screen Snippet (note: currently only works on mac):</p>
+        <button id='snippet'>get snippet</button>
+        <p>snippet output:</p>
+        <image id='snippet-img'/>
     </body>
     <script>
         var notfEl = document.getElementById('notf');
@@ -100,5 +106,27 @@
             SYM_API.setBadgeCount(0);
         });
 
+        var snippetButton = document.getElementById('snippet');
+        snippetButton.addEventListener('click', function() {
+            let snippet = new SYM_API.ScreenSnippet();
+
+            snippet
+            .capture()
+            .then(gotSnippet)
+            .catch(snippetError);
+
+            function gotSnippet(rsp) {
+                if (rsp && rsp.data && rsp.type) {
+                    var dataUrl = 'data:' + rsp.type + ',' + rsp.data;
+                    var img = document.getElementById('snippet-img');
+                    img.src = dataUrl;
+                }
+            }
+
+            function snippetError(err) {
+                alert('error getting snippet', err);
+            }
+        });
+
     </script>
 </html>

js/preload/preloadMain.js

@@ -25,6 +25,7 @@ const local = {
 };
 
 var notify = remote.require('./notify/notifyImpl.js');
+var ScreenSnippet = remote.require('./screenSnippet/ScreenSnippet.js');
 
 // throttle calls to this func to at most once per sec, called on leading edge.
 const throttledSetBadgeCount = throttle(1000, function(count) {
@@ -65,6 +66,12 @@ window.SYM_API = {
      */
     Notification: notify,
 
+    /**
+     * provides api to allow user to capture portion of screen, see api
+     * details in screenSnipper/ScreenSnippet.js
+     */
+    ScreenSnippet: ScreenSnippet,
+
     /**
      * allows JS to register a logger that can be used by electron main process.
      * @param  {Object} logger  function that can be called accepting

js/screenSnippet/ScreenSnippet.js

@@ -0,0 +1,141 @@
+'use strict';
+
+const childProcess = require('child_process');
+const fs = require('fs');
+const os = require('os');
+const path = require('path');
+
+const { isMac } = require('../utils/misc.js');
+
+// static ref to child process, only allow one screen snippet at time, so
+// hold ref to prev, so can kill before starting next snippet.
+let child;
+
+/**
+ * Captures a user selected portion of the monitor and returns jpeg image
+ * encoded in base64 format.
+ */
+class ScreenSnippet {
+    /**
+     * Returns promise.
+     *
+     * If successful will resolves with jpeg image encoded in base64 format:
+     * {
+     *     type: 'image/jpg;base64',
+     *     data: base64-data
+     * }
+     *
+     * Otherwise if not successful will reject with object
+     * containing: { type: ['WARN','ERROR'], message: String }
+     */
+    capture() {
+        return new Promise((resolve, reject) => {
+            let captureUtil, captureUtilArgs;
+
+            let tmpFilename = 'symphonyImage-' + Date.now() + '.jpg';
+            let tmpDir = os.tmpdir();
+
+            let outputFileName = path.join(tmpDir, tmpFilename);
+
+            if (isMac) {
+                // utilize Mac OSX built-in screencapture tool which has been
+                // available since OSX ver 10.2.
+                captureUtil = '/usr/sbin/screencapture';
+                captureUtilArgs = [ '-i', '-s', '-t', 'jpg', outputFileName ];
+            } else {
+                // for now screen snippet on windows is not supported,
+                // waiting on open sourcing for custom screen snippter util.
+                reject(this._createWarn('windows not supported'));
+                // custom built windows screen capture tool, that is
+                // located in same directory as running exec.
+                //captureUtil = './ScreenSnippet.exe';
+                //captureUtilArgs = [ outputFileName ];
+            }
+
+            // only allow one screen capture at a time.
+            if (child) {
+                child.kill();
+            }
+
+            child = childProcess.execFile(captureUtil, captureUtilArgs, (error) => {
+                // will be called when child process exits.
+                if (error && error.killed) {
+                    // processs was killed, just resolve with no data.
+                    resolve();
+                } else {
+                    this._readResult(outputFileName, resolve, reject, error);
+                }
+            });
+        });
+    }
+
+    // private methods below here
+
+    _readResult(outputFileName, resolve, reject, childProcessErr) {
+        fs.readFile(outputFileName, (readErr, data) => {
+            if (readErr) {
+                let returnErr;
+                if (readErr.code === 'ENOENT') {
+                    // no such file exists, user likely aborted
+                    // creating snippet. also include any error when
+                    // creating child process.
+                    returnErr = this._createWarn('file does not exist ' +
+                        childProcessErr);
+                } else {
+                    returnErr = this._createError(readErr + ',' +
+                        childProcessErr);
+                }
+
+                reject(returnErr);
+                return;
+            }
+
+            if (!data) {
+                reject(this._createWarn('no file data provided'));
+                return;
+            }
+
+            try {
+                // convert binary data to base64 encoded string
+                let output = Buffer(data).toString('base64');
+                resolve({
+                    type: 'image/jpg;base64',
+                    data: output
+                });
+            } catch (error) {
+                reject(this._createError(error));
+            }
+            finally {
+                // remove tmp file (async)
+                fs.unlink(outputFileName, function(removeErr) {
+                    // note: node complains if calling async
+                    // func without callback.
+                    /* eslint-disable no-console */
+                    if (removeErr) {
+                        console.error(
+                            'error removing temp snippet file: ' +
+                            outputFileName + ', err:' + removeErr);
+                    }
+                    /* eslint-enable no-console */
+                });
+            }
+        });
+
+    }
+
+    /* eslint-disable class-methods-use-this */
+    _createError(msg) {
+        var err = new Error(msg);
+        err.type = 'ERROR';
+        return err;
+    }
+
+    _createWarn(msg) {
+        var err = new Error(msg);
+        err.type = 'WARN';
+        return err;
+    }
+    /* eslint-enable class-methods-use-this */
+}
+
+module.exports = ScreenSnippet;

tests/ScreenSnippet.test.js

@@ -0,0 +1,128 @@
+
+const ScreenSnippet = require('../js/screenSnippet/ScreenSnippet.js');
+const path = require('path');
+const fs = require('fs');
+const os = require('os');
+
+const snippetBase64 = require('./fixtures/snippet/snippet-base64.js');
+
+// mock child_process used in ScreenSnippet
+jest.mock('child_process', function() {
+    return {
+        execFile: mockedExecFile
+    }
+});
+
+/**
+ * mock version of execFile just creates a copy of a test jpeg file.
+ */
+function mockedExecFile(util, args, doneCallback) {
+    let outputFileName = args[args.length - 1];
+
+    copyTestFile(outputFileName, function(copyTestFile) {
+        doneCallback();
+    });
+}
+
+function copyTestFile(destFile, done) {
+    const testfile = path.join(__dirname ,
+        'fixtures/snippet/ScreenSnippet.jpeg');
+
+    let reader = fs.createReadStream(testfile);
+    let writer = fs.createWriteStream(destFile);
+
+    writer.on('close', function() {
+        done();
+    });
+
+    reader.pipe(writer);
+}
+
+function createTestFile(done) {
+    let tmpDir = os.tmpdir();
+    const testFileName = path.join(tmpDir,
+        'ScreenSnippet-'  + Date.now() + '.jpeg');
+
+    copyTestFile(testFileName, function() {
+        done(testFileName)
+    });
+}
+
+
+
+describe('Tests for ScreenSnippet', function() {
+    describe('when reading a valid jpeg file', function() {
+        it('should match base64 output', function(done) {
+            let s = new ScreenSnippet();
+            s.capture().then(gotImage);
+
+            function gotImage(rsp) {
+                expect(rsp.type).toEqual('image/jpg;base64');
+                expect(rsp.data).toEqual(snippetBase64);
+                done();
+            };
+        });
+
+        it('should remove output file after completed', function(done) {
+            createTestFile(function(testfileName) {
+                let s = new ScreenSnippet();
+                s._readResult(testfileName, resolve);
+
+                function resolve() {
+                    // should be long enough before file
+                    // gets removed
+                    setTimeout(function() {
+                        let exists = fs.existsSync(testfileName);
+                        expect(exists).toBe(false);
+                        done();
+                    }, 2000);
+                }
+            });
+        });
+    });
+
+    it('should fail if output file does not exist', function(done) {
+        let s = new ScreenSnippet();
+        let nonExistentFile = 'bogus.jpeg'
+        s._readResult(nonExistentFile, resolve, reject);
+
+        function resolve() {
+            // shouldn't get here
+            expect(true).toBe(false);
+        }
+
+        function reject(err) {
+            expect(err).toBeTruthy();
+            done();
+        }
+    });
+
+    it('should fail if read file fails', function(done) {
+        var origFsReadFile = fs.readFile;
+
+        fs.readFile = jest.fn(mockedReadFile);
+
+        function mockedReadFile(filename, callback) {
+            callback(new Error('failed'));
+        }
+
+        let s = new ScreenSnippet();
+        s.capture().then(resolved).catch(rejected);
+
+        function resolved(err) {
+            cleanup();
+            // shouldn't get here
+            expect(true).toBe(false);
+        }
+
+        function rejected(err) {
+            expect(err).toBeTruthy();
+            cleanup();
+            done();
+        }
+
+        function cleanup() {
+            fs.readFile = origFsReadFile;
+        }
+    });
+});

tests/fixtures/snippet/snippet-base64.js

@@ -0,0 +1,5 @@
+// base64 conversion of file ScreenSnippet.jpeg
+const base64ScreenSnippet =
+"/9j/4AAQSkZJRgABAQEASABIAAD/4QB0RXhpZgAATU0AKgAAAAgABAEaAAUAAAABAAAAPgEbAAUAAAABAAAARgEoAAMAAAABAAIAAIdpAAQAAAABAAAATgAAAAAAAABIAAAAAQAAAEgAAAABAAKgAgAEAAAAAQAAAEOgAwAEAAAAAQAAADsAAAAA/+0AOFBob3Rvc2hvcCAzLjAAOEJJTQQEAAAAAAAAOEJJTQQlAAAAAAAQ1B2M2Y8AsgTpgAmY7PhCfv/iAoRJQ0NfUFJPRklMRQABAQAAAnRhcHBsBAAAAG1udHJSR0IgWFlaIAfcAAsADAASADoAF2Fjc3BBUFBMAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAD21gABAAAAANMtYXBwbGZJ+dk8hXeftAZKmR46dCwAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAC2Rlc2MAAAEIAAAAY2RzY20AAAFsAAA" + "ALGNwcnQAAAGYAAAALXd0cHQAAAHIAAAAFHJYWVoAAAHcAAAAFGdYWVoAAAHwAAAAFGJYWVoAAAIEAAAAFHJUUkMAAAIYAAAAEGJUUkMAAAIoAAAAEGdUUkMAAAI4AAAAEGNoYWQAAAJIAAAALGRlc2MAAAAAAAAACUhEIDcwOS1BAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAABtbHVjAAAAAAAAAAEAAAAMZW5VUwAAABAAAAAcAEgARAAgADcAMAA5AC0AQXRleHQAAAAAQ29weXJpZ2h0IEFwcGxlIENvbXB1dGVyLCBJbmMuLCAyMDEwAAAAAFhZWiAAAAAAAADzUgABAAAAARbPWFlaIAAAAAAAAG+hAAA5IwAAA4xYWVogAAAAAAAAYpYAALe8AAAYylhZWiAAAA" + "AAAAAkngAADzsAALbOcGFyYQAAAAAAAAAAAAH2BHBhcmEAAAAAAAAAAAAB9gRwYXJhAAAAAAAAAAAAAfYEc2YzMgAAAAAAAQxCAAAF3v//8yYAAAeSAAD9kf//+6L///2jAAAD3AAAwGz/wAARCAA7AEMDASIAAhEBAxEB/8QAHwAAAQUBAQEBAQEAAAAAAAAAAAECAwQFBgcICQoL/8QAtRAAAgEDAwIEAwUFBAQAAAF9AQIDAAQRBRIhMUEGE1FhByJxFDKBkaEII0KxwRVS0fAkM2JyggkKFhcYGRolJicoKSo0NTY3ODk6Q0RFRkdISUpTVFVWV1hZWmNkZWZnaGlqc3R1dnd4eXqDhIWGh4iJipKTlJWWl5iZmqKjpKWmp6ipqrKztLW2t7i5usLDxMXGx8jJytLT1NXW19jZ2uHi4+Tl5ufo6erx8vP09fb3+Pn6/8QAHwEAAwEBAQEBAQEBAQAAAAAAAAECAwQFB" + "gcICQoL/8QAtREAAgECBAQDBAcFBAQAAQJ3AAECAxEEBSExBhJBUQdhcRMiMoEIFEKRobHBCSMzUvAVYnLRChYkNOEl8RcYGRomJygpKjU2Nzg5OkNERUZHSElKU1RVVldYWVpjZGVmZ2hpanN0dXZ3eHl6goOEhYaHiImKkpOUlZaXmJmaoqOkpaanqKmqsrO0tba3uLm6wsPExcbHyMnK0tPU1dbX2Nna4uPk5ebn6Onq8vP09fb3+Pn6/9sAQwACAgICAgIDAgIDBQMDAwUGBQUFBQYIBgYGBgYICggICAgICAoKCgoKCgoKDAwMDAwMDg4ODg4PDw8PDw8PDw8P/9sAQwECAgIEBAQHBAQHEAsJCxAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQEBAQ/90ABAAF/9oADAMBAAIRAxEAPwD8u6KK9e+H3gqG9Rde1ePfDn9xEw4b" + "H8bDuPQd+vTr7+CwU69RU4Hw3EXEOHyzCyxWIei0S6t9kcZongvX9dRZrWDyrduksp2qfp1J/AYrt4vhFcFczaoqN6LEWH5lh/KvbQAAABgClr7ahw3h4r31zP8Arsfznmfi9m1abeHapx6JJN/NyT/BI+RviL8CfFWqQW02gzwXrW3mZjYmJ237cbd2V7d2FfJ+r6NqugXz6ZrVpJZXUf3o5VKnB6EZ6g9iODX601xfjjwHoPj3SH0zWYgJAD5NwoHmwv2Kn09V6H8jXnZlwnTmnKg7Pt0PouFvGvFUqkaWZxU4fzJWkvOy0a8rJ/kflvRXR+LPDGpeDtfu/D2qria1bAYZ2yIeVdc9mHP6Hmucr8+qU3GTjJWaP6dw2IhWpxq0neMldPumFFFFQbH/0PzL0mwbVNUtNOU4+0yKhPoCeT+A5r67hhit4Y7eBQkcShVUdAqjAFfMPgIqPGOmh+haT8/LbH619R1+l8LUl7K" + "c+t7f195/KfjZjJvGUMP9lR5vm21/7aFeq/CzwVpPjT/hL/7WeVP7C8O6hqsHlMFzPa7NgfIOV+Y5Awfeua8FS+AodWkb4iW2o3Om+SwRdMlhhmE25dpYzI6lNu7IABzjnqD9d/Bm7/Z9f/hOv+Ed03xLFt8K6mbz7VdWj7rMeX5qxbIVxKeNpbKjnINexj8TKEHyxfqfnvDGUU8RXg6lSNtfdbd9n5fqfClFe46xefs4NpN4ug6X4pj1IwuLZri8smhE207DIFgDFA2NwBBI6Eda8OrspVXL7LXqeFjcGqLSVSMr/wAt/wBUj5Z/ae8MxXOiad4shQefZy/ZpSOpilyVz/usOP8AeNfFNfox8fvL/wCFVaxv+9uttv18+P8Apmvznr824soqOLuuqT/Nfof1h4LY6dbJeSf2JyivSyl+cmFFFFfMn62f/9H8xdO1BtJ1Sz1RBn7NKrkDuoPI/EcV9gwTxXMEdzAweKVQ6s" + "OhVhkH8RXxk67lIr1P4c+OodNVfDutybIM/uJmPCZ/gY9hnoe3TpX3HDuYxpTdKbsn+f8AwT8F8WuE6uNoQxmGjedO6aW7j5ej6dmz3+vTfhp45sfA/wDwlf263kuP7f0C+0iLy8fJLd7Nrtkj5Rt5xzXmIIYBlOQehpa+4qU1OPLLY/mrCYqdCoqtPdf8MFFFcX448eaD4C0h9T1mUGQg+TbqR5sz9go9PVug/IUVasYRc5uyQ8FgquIqxoUIuUpaJI8N/ae8TRW2iad4ThcefeS/aZQOoiiyFz/vMeP9018U10fizxPqXjHX7vxDqrZmumyFGdsaDhUXPZRx+p5rnK/Is4x/1nESqLbp6H9wcD8N/wBlZbTwktZby/xPf7tvkFFFFeYfXH//0vy7qvNCHFWKK9Q8RM2ND8a+J/DaLb2dwJrZekMw3oB6DoR9AQK7mL41Xipi40dHb1WYqPyKN/OvK2AqEquelehQzXEUl" + "ywm7ff+Z8tmXA2U4ybqYjDpye7V4t+vK1f5mv4++Pni2wggh0O2t7A3G/MjAzOu3GNu7C9+6mvljV9Z1XX759T1q7kvbqT70krFmwOgGegHYDgV9If8I3ouvD/ibW3n+R9z53XG7r90r6DrTv8AhXHgz/oH/wDkaX/4uvPx2Mr13+8ndf10PcyHh3Lsvj/slFRb3a1f3vX8T5aor6l/4Vx4M/6B/wD5Gl/+Lo/4Vx4M/wCgf/5Gl/8Ai64PZM+i9sj5aor6l/4Vx4M/6B//AJGl/wDi6P8AhXHgz/oH/wDkaX/4uj2TD2yP/9k="
+
+module.exports = base64ScreenSnippet