mus: Implement ScreenMus::GetCursorScreenPoint().

components/mus/public/cpp/lib/window_tree_client_impl.cc

 // Copyright 2014 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 "components/mus/public/cpp/lib/window_tree_client_impl.h"
 
 #include <stddef.h>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 113 matching lines @@
     : connection_id_(0),
       next_window_id_(1),
       next_change_id_(1),
       delegate_(delegate),
       window_manager_delegate_(window_manager_delegate),
       capture_window_(nullptr),
       focused_window_(nullptr),
       binding_(this),
       tree_(nullptr),
       delete_on_no_roots_(true),
-      in_destructor_(false) {
+      in_destructor_(false),
+      called_initialize_cursor_location_(false),
+      cursor_location_memory_(nullptr),
+      weak_factory_(this) {
   // Allow for a null request in tests.
   if (request.is_pending())
     binding_.Bind(std::move(request));
   if (window_manager_delegate)
     window_manager_delegate->SetWindowManagerClient(this);
 }
 
 WindowTreeClientImpl::~WindowTreeClientImpl() {
   in_destructor_ = true;
 
@@ skipping 377 matching lines @@
   WindowPrivate(root).LocalSetParentDrawn(drawn);
 
   delegate_->OnEmbed(root);
 
   if (focused_window_) {
     FOR_EACH_OBSERVER(WindowTreeConnectionObserver, observers_,
                       OnWindowTreeFocusChanged(focused_window_, nullptr));
   }
 }
 
+void WindowTreeClientImpl::OnReceivedCursorLocationMemory(
+    mojo::ScopedSharedBufferHandle handle) {
+  cursor_location_handle_ = std::move(handle);
+  MojoResult result = mojo::MapBuffer(
+      cursor_location_handle_.get(), 0,
+      sizeof(base::subtle::Atomic32),
+      reinterpret_cast<void**>(&cursor_location_memory_),
+      MOJO_MAP_BUFFER_FLAG_NONE);
+  if (result != MOJO_RESULT_OK) {
+    NOTREACHED();
+    return;
+  }
+  DCHECK(cursor_location_memory_);
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // WindowTreeClientImpl, WindowTreeConnection implementation:
 
 void WindowTreeClientImpl::SetDeleteOnNoRoots(bool value) {
   delete_on_no_roots_ = value;
 }
 
 const std::set<Window*>& WindowTreeClientImpl::GetRoots() {
   return roots_;
 }
 
 Window* WindowTreeClientImpl::GetFocusedWindow() {
   return focused_window_;
 }
 
 void WindowTreeClientImpl::ClearFocus() {
   if (!focused_window_)
     return;
 
   SetFocus(nullptr);
 }
 
+void WindowTreeClientImpl::InitializeCursorLocation() {
+  called_initialize_cursor_location_ = true;

[sky, 2016/04/27 20:10:28]

DCHECK(!called...?

+  tree_ptr_->GetCursorLocationMemory(
+      base::Bind(&WindowTreeClientImpl::OnReceivedCursorLocationMemory,
+                 weak_factory_.GetWeakPtr()));
+}
+
+gfx::Point WindowTreeClientImpl::GetCursorScreenPoint() {
+  CHECK(called_initialize_cursor_location_);
+
+  // We raced initialization. Return (0, 0).
+  if (!cursor_location_memory_)
+    return gfx::Point();
+
+  base::subtle::Atomic32 location =
+      base::subtle::NoBarrier_Load(cursor_location_memory_);
+  return gfx::Point(location >> 16, location & 0xFFFF);

[sky, 2016/04/27 20:10:28]

I believe the way you have this code means we can't have negative coordinates. I
suspect we want them. How about supporting the sign bit?

+}
+
 Window* WindowTreeClientImpl::NewWindow(
     const Window::SharedProperties* properties) {
   return NewWindowImpl(NewWindowType::CHILD, properties);
 }
 
 Window* WindowTreeClientImpl::NewTopLevelWindow(
     const Window::SharedProperties* properties) {
   Window* window = NewWindowImpl(NewWindowType::TOP_LEVEL, properties);
   // Assume newly created top level windows are drawn by default, otherwise
   // requests to focus will fail. We will get the real value in
@@ skipping 477 matching lines @@
 
 void WindowTreeClientImpl::SetUnderlaySurfaceOffsetAndExtendedHitArea(
     Window* window,
     const gfx::Vector2d& offset,
     const gfx::Insets& hit_area) {
   window_manager_internal_client_->SetUnderlaySurfaceOffsetAndExtendedHitArea(
       server_id(window), offset.x(), offset.y(), mojo::Insets::From(hit_area));
 }
 
 }  // namespace mus