[Chromecast] Add input support.

ui/events/ozone/evdev/event_thread_evdev.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/events/ozone/evdev/event_thread_evdev.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 25 matching lines @@
 
   void Init() override {
     TRACE_EVENT0("evdev", "EvdevThread::Init");
     input_device_factory_ =
         new InputDeviceFactoryEvdev(std::move(dispatcher_), cursor_);
 
     std::unique_ptr<InputDeviceFactoryEvdevProxy> proxy(
         new InputDeviceFactoryEvdevProxy(base::ThreadTaskRunnerHandle::Get(),
                                          input_device_factory_->GetWeakPtr()));
 
-    cursor_->InitializeOnEvdev();
+    if (cursor_)

[derekjchow1, 2017/01/13 18:12:28]

Can Cast provide its own CursorDelegateEvdev? If so, we could provide a no-op
InitializeOnEvdev implementation and remove the need for this if-statement.

[Joshua LeVasseur, 2017/01/13 23:38:13]

Glancing through the evdev code, it seems to be designed to handle a null
cursor_ (it totally used to handle a null cursor_ when I started prototyping
this code).  We don't support a mouse, so a nullptr seems appropriate, rather
than a no-op CursorDelegateEvdev --- but I'm guessing about intentions of the
evdev layer.

[spang, 2017/01/16 18:54:54]

Yes, it did support null, it just breaks from time to time because it has no
integration test coverage (CrOS tests use the cursor, obviously, so the non-null
case gets tested). Would be good to fix that.

A stub CursorDelegateEvdev does not have quite the same effect as a null one - a
stub that always reports a position of (0,0) would cause a CSS hover effect
there, for example.

+      cursor_->InitializeOnEvdev();
 
     init_runner_->PostTask(FROM_HERE,
                            base::Bind(init_callback_, base::Passed(&proxy)));
   }
 
   void CleanUp() override {
     TRACE_EVENT0("evdev", "EvdevThread::CleanUp");
     delete input_device_factory_;
   }
 
@@ skipping 23 matching lines @@
   TRACE_EVENT0("evdev", "EventThreadEvdev::Start");
   thread_.reset(new EvdevThread(std::move(dispatcher), cursor, callback));
   base::Thread::Options thread_options;
   thread_options.message_loop_type = base::MessageLoop::TYPE_UI;
   thread_options.priority = base::ThreadPriority::DISPLAY;
   if (!thread_->StartWithOptions(thread_options))
     LOG(FATAL) << "Failed to create input thread";
 }
 
 }  // namespace ui