Back to Top: Make sure to re-check the visibility after the scrolling is done

If a user scrolls just below the 1000px threshold and clicks the back-to-top button within 250ms, we'll never hide the button as the scroll event gets throttled away. That's rather inconvenient.

closes #7729

Changelog.md

@@ -13,6 +13,7 @@
 
 ## Features
 * Add basic html5 audio/video embedding support [#6418](https://github.com/diaspora/diaspora/pull/6418)
+* Add the back-to-top button to all pages [#7729](https://github.com/diaspora/diaspora/pull/7729)
 
 # 0.7.3.1
 

app/assets/javascripts/app/views/back_to_top_view.js

@@ -12,7 +12,7 @@ app.views.BackToTop = Backbone.View.extend({
 
   backToTop: function(evt) {
     evt.preventDefault();
-    $("html, body").animate({scrollTop: 0});
+    $("html, body").animate({scrollTop: 0}, this.toggleVisibility);
   },
 
   toggleVisibility: function() {

spec/javascripts/app/views/back_to_top_view_spec.js

@@ -17,7 +17,7 @@ describe("app.views.BackToTop", function() {
     it("scrolls to the top of the page", function() {
       var spy = spyOn($.fn, "animate");
       this.view.backToTop($.Event());
-      expect(spy).toHaveBeenCalledWith({scrollTop: 0});
+      expect(spy).toHaveBeenCalledWith({scrollTop: 0}, jasmine.any(Function));
     });
   });