* Electron version: 1.6.10
* Operating system: macOS Sierra 10.12.4 (16E195)

# Improve Handoff API support

Hi!

Today the API of Handoff provides the methods: `setUserActivity`, `getCurrentActivityType` and dispatch the event `continue-activity`

I'm using Handoff and noticed that in some circumstances the broadcast takes a long time to update its userInfo which does not happen on the native iOS client

1. To invalidate or resign the current activity we currently need to create a non-existing activity type and set it as the current activity. There's no way to handle the activity life cycle through electron.
2. When we need to update a given user activity userInfo frequently (i.e in response to a search bar's text changes), we have no efficient way. Setting a new userActivity with the updated information takes several seconds to bridge, whereas doing this on iOS native app is instantaneous.

I believe that exposing a bit more of the NSUserActivity API to Electron would help, namely `becomeCurrent`, `resignCurrent` and `invalidate` which would address point 1, and `needsSave` and a new event to allow updating an activity when needed to address point 2.
These are described in more detail in https://developer.apple.com/reference/foundation/nsuseractivity.

I'm are open to help in any way i can such as explaining how the native API work, providing sample code or testing possible implementations

Thank you!
atom/browser/api/atom_api_app.cc
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#endif  
v8::Local<v8::Promise> App::GetFileIcon(const base::FilePath& path,
                                        mate::Arguments* args) {
  util::Promise promise(isolate());
  v8::Local<v8::Promise> handle = promise.GetHandle();
  base::FilePath normalized_path = path.NormalizePathSeparators();
  IconLoader::IconSize icon_size;
  mate::Dictionary options;
  if (!args->GetNext(&options)) {
    icon_size = IconLoader::IconSize::NORMAL;
  } else {
    std::string icon_size_string;
    options.Get("size", &icon_size_string);
    icon_size = GetIconSizeByString(icon_size_string);
  }
  auto* icon_manager = AtomBrowserMainParts::Get()->GetIconManager();
  gfx::Image* icon =
      icon_manager->LookupIconFromFilepath(normalized_path, icon_size);
  if (icon) {
    promise.Resolve(*icon);
  } else {
    icon_manager->LoadIcon(
        normalized_path, icon_size,
        base::BindOnce(&OnIconDataAvailable, std::move(promise)),
        &cancelable_task_tracker_);
  }
  return handle;
}
std::vector<mate::Dictionary> App::GetAppMetrics(v8::Isolate* isolate) {