Updates shadow when active window changes

mash/wm/shadow_controller.cc

Index: mash/wm/shadow_controller.cc
diff --git a/mash/wm/shadow_controller.cc b/mash/wm/shadow_controller.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b7f91f130149c9a99c111bcf1dbbf1aca5b7d0a9
--- /dev/null
+++ b/mash/wm/shadow_controller.cc
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+// 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 "mash/wm/shadow_controller.h"
+
+#include "components/mus/public/cpp/window.h"
+#include "components/mus/public/cpp/window_tree_connection.h"
+#include "mash/wm/property_util.h"
+#include "mash/wm/shadow.h"
+
+namespace mash {
+namespace wm {
+namespace {
+
+// Returns the first ancestor of |from| (including |from|) that has a shadow.
+mus::Window* FindAncestorWithShadow(mus::Window* from) {
+  mus::Window* result = from;
+  while (result && !GetShadow(result))
+    result = result->parent();
+  // Small shadows never change.
+  return result && GetShadow(result)->style() != Shadow::STYLE_SMALL ? result
+                                                                     : nullptr;
+}
+
+}  // namespace
+
+ShadowController::ShadowController(mus::WindowTreeConnection* window_tree)
+    : window_tree_(window_tree), active_window_(nullptr) {
+  window_tree_->AddObserver(this);
+  SetActiveWindow(FindAncestorWithShadow(window_tree_->GetFocusedWindow()));
+}
+
+ShadowController::~ShadowController() {
+  window_tree_->RemoveObserver(this);
+  if (active_window_)
+    active_window_->RemoveObserver(this);
+}
+
+void ShadowController::SetActiveWindow(mus::Window* window) {
+  if (window == active_window_)
+    return;
+
+  if (active_window_) {
+    GetShadow(active_window_)->SetStyle(Shadow::STYLE_INACTIVE);
+    active_window_->RemoveObserver(this);
+  }
+  active_window_ = window;
+  if (active_window_) {
+    GetShadow(active_window_)->SetStyle(Shadow::STYLE_ACTIVE);
+    active_window_->AddObserver(this);
+  }
+}
+
+void ShadowController::OnWindowTreeFocusChanged(mus::Window* gained_focus,
+                                                mus::Window* lost_focus) {
+  SetActiveWindow(FindAncestorWithShadow(gained_focus));
+}
+
+void ShadowController::OnWindowDestroying(mus::Window* window) {
+  DCHECK_EQ(window, active_window_);
+  SetActiveWindow(nullptr);
+}
+
+}  // namespace wm
+}  // namespace mash