first attempt at integrating subset of FileSaver.js for Safari download support

Author: timelyportfolio

src/snapshot/download.js

@@ -10,6 +10,7 @@
 'use strict';
 
 var toImage = require('../plot_api/to_image');
+var fileSaver = require('./filesaver');
 
 /**
  * @param {object} gd figure Object
@@ -41,18 +42,11 @@ function downloadImage(gd, opts) {
 
         promise.then(function(result) {
             gd._snapshotInProgress = false;
-
-            var downloadLink = document.createElement('a');
-            downloadLink.href = result;
-            downloadLink.download = filename; // only supported by FF and Chrome
-
-            document.body.appendChild(downloadLink);
-            downloadLink.click();
-            document.body.removeChild(downloadLink);
-            resolve(filename);
+            return fileSaver(result,filename);
+        }).then(function(name){
+            resolve(name);
         }).catch(function(err) {
             gd._snapshotInProgress = false;
-            console.error(err);
             reject(err);
         });
     });

src/snapshot/filesaver.js

@@ -0,0 +1,62 @@
+/*
+substantial portions of this code from FileSaver.js
+https://github.com/eligrey/FileSaver.js
+License: https://github.com/eligrey/FileSaver.js/blob/master/LICENSE.md
+*/
+
+/* FileSaver.js
+ * A saveAs() FileSaver implementation.
+ * 1.1.20160328
+ *
+ * By Eli Grey, http://eligrey.com
+ * License: MIT
+ *   See https://github.com/eligrey/FileSaver.js/blob/master/LICENSE.md
+ */
+
+
+'use strict';
+  
+var saveLink = document.createElementNS("http://www.w3.org/1999/xhtml", "a");
+var canUseSaveLink = "download" in saveLink;
+var isSafari = /Version\/[\d\.]+.*Safari/.test(navigator.userAgent);
+
+var fileSaver = function(url, name) {
+    var promise = new Promise(function(resolve, reject) {
+      	// IE <10 is explicitly unsupported
+      	if (typeof navigator !== "undefined" && /MSIE [1-9]\./.test(navigator.userAgent)) {
+      		  reject(new Error("IE < 10 unsupported"));
+      	}
+      	
+    		// First try a.download, then web filesystem, then object URLs
+    		if (isSafari) {
+            // Safari doesn't allow downloading of blob urls
+            document.location.href = "data:attachment/file" + url.slice(url.search(/[,;]/));
+            resolve(name);
+        }
+        
+    		if (!name) {
+      			name = "download";
+    		}
+    		
+    		if (canUseSaveLink) {
+            saveLink.href = url;
+            saveLink.download = name;
+            document.body.appendChild(saveLink);
+            saveLink.click();
+            document.body.removeChild(saveLink);
+            resolve(name);
+    		}
+    		
+    	  // IE 10+ (native saveAs)
+    	  if (typeof navigator !== "undefined" && navigator.msSaveOrOpenBlob) {
+            navigator.msSaveOrOpenBlob(url, name);
+            resolve(name);
+        }
+        
+        reject(new Error('download error'));
+    });
+    
+    return promise;
+};
+
+module.exports = fileSaver;