mus: Implement ScreenMus::GetCursorScreenPoint().

components/mus/ws/user_display_manager.cc

 // Copyright 2016 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/ws/user_display_manager.h"
 
 #include "components/mus/ws/display.h"
 #include "components/mus/ws/display_manager.h"
 #include "components/mus/ws/window_manager_state.h"
 
 namespace mus {
 namespace ws {
 
 UserDisplayManager::UserDisplayManager(ws::DisplayManager* display_manager,
                                        const UserId& user_id)
-    : display_manager_(display_manager), user_id_(user_id) {
+    : display_manager_(display_manager),
+      user_id_(user_id),
+      current_cursor_location_(0),
+      cursor_location_memory_(nullptr) {
   for (const WindowManagerState* wms : GetWindowManagerStatesForUser()) {
     if (wms->got_frame_decoration_values()) {
       got_valid_frame_decorations_ = true;
       break;
     }
   }
 }
 
 UserDisplayManager::~UserDisplayManager() {}
 
@@ skipping 28 matching lines @@
   }
 
   display_manager_observers_.ForAllPtrs(
       [this, &display](mojom::DisplayManagerObserver* observer) {
         observer->OnDisplayRemoved(display->id());
       });
   if (test_observer_)
     test_observer_->OnDisplayRemoved(display->id());
 }
 
+void UserDisplayManager::OnMouseCursorLocationChanged(const gfx::Point& point) {
+  current_cursor_location_ =
+      static_cast<base::subtle::Atomic32>(
+          (point.x() & 0xFFFF) << 16 | (point.y() & 0xFFFF));

[sky, 2016/04/27 23:55:57]

Seems like this loses the sign bit, but again, I could be wrong. How about a
test with a negative x/y?

[Elliot Glaysher, 2016/04/28 00:14:01]

Added unit test to user_display_manager_unittest.cc, which exercises this code.
(I'm not sure how to test the WindowTreeClientImpl code.)

+  if (cursor_location_memory_) {
+    base::subtle::NoBarrier_Store(cursor_location_memory_,
+                                  current_cursor_location_);
+  }
+}
+
+mojo::ScopedSharedBufferHandle UserDisplayManager::GetCursorLocationMemory() {
+  if (!cursor_location_memory_) {
+    // Create our shared memory segment to share the cursor state with our
+    // window clients.
+    MojoResult result = mojo::CreateSharedBuffer(nullptr,
+                                                 sizeof(base::subtle::Atomic32),
+                                                 &cursor_location_handle_);
+    if (result != MOJO_RESULT_OK)
+      return mojo::ScopedSharedBufferHandle();
+    DCHECK(cursor_location_handle_.is_valid());
+
+    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)
+      return mojo::ScopedSharedBufferHandle();
+    DCHECK(cursor_location_memory_);
+
+    base::subtle::NoBarrier_Store(cursor_location_memory_,
+                                  current_cursor_location_);
+  }
+
+  mojo::ScopedSharedBufferHandle duped;
+  MojoDuplicateBufferHandleOptions options = {
+    sizeof(MojoDuplicateBufferHandleOptions),
+    MOJO_DUPLICATE_BUFFER_HANDLE_OPTIONS_FLAG_READ_ONLY
+  };
+  MojoResult result = mojo::DuplicateBuffer(cursor_location_handle_.get(),
+                                            &options, &duped);
+  if (result != MOJO_RESULT_OK)
+    return mojo::ScopedSharedBufferHandle();
+  DCHECK(duped.is_valid());
+
+  return duped;
+}
+
+
 std::set<const WindowManagerState*>
 UserDisplayManager::GetWindowManagerStatesForUser() const {
   std::set<const WindowManagerState*> result;
   for (const Display* display : display_manager_->displays()) {
     const WindowManagerState* wms =
         display->GetWindowManagerStateForUser(user_id_);
     if (wms && wms->got_frame_decoration_values())
       result.insert(wms);
   }
   return result;
@@ skipping 40 matching lines @@
 
 void UserDisplayManager::AddObserver(
     mojom::DisplayManagerObserverPtr observer) {
   mojom::DisplayManagerObserver* observer_impl = observer.get();
   display_manager_observers_.AddPtr(std::move(observer));
   OnObserverAdded(observer_impl);
 }
 
 }  // namespace ws
 }  // namespace mus