filename as Optional argument

atom/browser/api/atom_api_window.cc

@@ -729,8 +729,11 @@ void Window::SetAspectRatio(double aspect_ratio, mate::Arguments* args) {
   window_->SetAspectRatio(aspect_ratio, extra_size);
 }
 
-void Window::PreviewFile(const std::string& filepath,
-                         const std::string& filename) {
+void Window::PreviewFile(const std::string& filepath, mate::Arguments* args) {
+  std::string filename;
+  if (!args->GetNext(&filename)) {
+    filename = filepath;
+  } 
   window_->PreviewFile(filepath, filename);
 }
 

atom/browser/api/atom_api_window.h

@@ -170,7 +170,7 @@ class Window : public mate::TrackableObject<Window>,
   void SetMenuBarVisibility(bool visible);
   bool IsMenuBarVisible();
   void SetAspectRatio(double aspect_ratio, mate::Arguments* args);
-  void PreviewFile(const std::string& filepath, const std::string& filename);
+  void PreviewFile(const std::string& filepath, mate::Arguments* args);
   void SetParentWindow(v8::Local<v8::Value> value, mate::Arguments* args);
   v8::Local<v8::Value> GetParentWindow() const;
   std::vector<v8::Local<v8::Object>> GetChildWindows() const;

docs/api/browser-window.md

@@ -664,10 +664,12 @@ the player itself we would call this function with arguments of 16/9 and
 are within the content view--only that they exist. Just sum any extra width and
 height areas you have within the overall content view.
 
-#### `win.previewFile(pathname, filename)` _macOS_
+#### `win.previewFile(pathname[, filename])` _macOS_
 
 * `pathname` String - The absolute path to the file to preview with QuickLook. This is important as Quicklook uses the file name and file extension on the path to determine the content_type of the file to open.
-* `filename` String - The name of the file to display on QuickLook modal view. This is purely visual and does not affect the content_type of the file.
+* `filename` String (Optional) - The name of the file to display on the QuickLook modal view. This is purely visual and does not affect the content_type of the file. Defaults to filepath.
+
+Uses QuickLook to preview a file at a given path.
 
 #### `win.setBounds(bounds[, animate])`