Support metaKey and ctrlKey for selection.

MetaKey is the windows key on Windows/Linux. Using only that for
selecting items is really confusing, because AFAIK no existing
application does that. With this commit, ctrl can be used for selecting
items as well.

src/scripts/multiselect.js

@@ -3,6 +3,12 @@
  * @copyright   2015 by Tobias Reich
  */
 
+const isSelectKeyPressed = function(e) {
+
+	return e.metaKey || e.ctrlKey
+
+}
+
 multiselect = {
 
 	ids: []
@@ -71,8 +77,8 @@ multiselect.albumClick = function(e, albumObj) {
 
 	let id = albumObj.attr('data-id')
 
-	if (e.metaKey===true) multiselect.toggleItem(albumObj, id)
-	else                  lychee.goto(id)
+	if (isSelectKeyPressed(e)) multiselect.toggleItem(albumObj, id)
+	else                       lychee.goto(id)
 
 }
 
@@ -80,8 +86,8 @@ multiselect.photoClick = function(e, photoObj) {
 
 	let id = photoObj.attr('data-id')
 
-	if (e.metaKey===true) multiselect.toggleItem(photoObj, id)
-	else                  lychee.goto(album.getID() + '/' + id)
+	if (isSelectKeyPressed(e)) multiselect.toggleItem(photoObj, id)
+	else                       lychee.goto(album.getID() + '/' + id)
 
 }
 
@@ -251,7 +257,7 @@ multiselect.getSelection = function(e) {
 	if (visible.contextMenu())  return false
 	if (!visible.multiselect()) return false
 
-	if (e.metaKey===false && (size.width==0 || size.height==0)) {
+	if (!isSelectKeyPressed(e) && (size.width==0 || size.height==0)) {
 		multiselect.close()
 		return false
 	}