Reorder the NativeViews attached to a view via kViewHostKey according to the position of the view

ui/views/widget/window_reorderer.cc

+// Copyright (c) 2013 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/views/widget/window_reorderer.h"
+
+#include <map>
+#include <vector>
+
+#include "ui/aura/window.h"
+#include "ui/views/view.h"
+#include "ui/views/view_constants_aura.h"
+
+namespace views {
+
+namespace {
+
+// Sets |hosted_windows| to a mapping of the views with an associated window to
+// the window that they are associated to. Only views associated to a child of
+// |parent_window| are returned.
+void GetViewsWithAssociatedWindow(
+    const aura::Window& parent_window,
+    std::map<views::View*, aura::Window*>* hosted_windows) {
+  const std::vector<aura::Window*>& child_windows = parent_window.children();
+  for (size_t i = 0; i < child_windows.size(); ++i) {
+    aura::Window* child = child_windows[i];
+    View* host_view = child->GetProperty(kHostViewKey);
+    if (host_view)
+      (*hosted_windows)[host_view] = child;
+  }
+}
+
+// Sets |order| to the list of views whose layer / associated window's layer
+// is a child of |parent_layer|. |order| is sorted in ascending z-order of
+// the views.
+// |hosts| are the views with an associated window whose layer is a child of
+// |parent_layer|.
+void GetOrderOfViewsWithLayers(
+    views::View* view,
+    ui::Layer* parent_layer,
+    const std::map<views::View*, aura::Window*>& hosts,
+    std::vector<views::View*>* order) {
+  DCHECK(view);
+  DCHECK(parent_layer);
+  DCHECK(order);
+  if (view->layer() && view->layer()->parent() == parent_layer) {
+    order->push_back(view);
+    // |hosts| may contain a child of |view|.
+  } else if (hosts.find(view) != hosts.end()) {
+    order->push_back(view);
+  }
+
+  for (int i = 0; i < view->child_count(); ++i)
+    GetOrderOfViewsWithLayers(view->child_at(i), parent_layer, hosts, order);
+}
+
+}  // namespace
+
+// Class which reorders windows as a result of the kHostViewKey property being
+// set on the window.
+class WindowReorderer::AssociationObserver : public aura::WindowObserver {
+ public:
+  explicit AssociationObserver(WindowReorderer* reorderer);
+  virtual ~AssociationObserver();
+
+  // Start/stop observing changes in the kHostViewKey property on |window|.
+  void StartObserving(aura::Window* window);
+  void StopObserving(aura::Window* window);
+
+ private:
+  // aura::WindowObserver overrides:
+  virtual void OnWindowPropertyChanged(aura::Window* window,
+                                      const void* key,
+                                      intptr_t old) OVERRIDE;
+  virtual void OnWindowDestroying(aura::Window* window) OVERRIDE;
+
+  // Not owned.
+  WindowReorderer* reorderer_;
+
+  std::set<aura::Window*> windows_;
+
+  DISALLOW_COPY_AND_ASSIGN(AssociationObserver);
+};
+
+WindowReorderer::AssociationObserver::AssociationObserver(
+    WindowReorderer* reorderer)
+    : reorderer_(reorderer) {
+}
+
+WindowReorderer::AssociationObserver::~AssociationObserver() {
+  while (!windows_.empty())
+    StopObserving(*windows_.begin());
+}
+
+void WindowReorderer::AssociationObserver::StartObserving(
+    aura::Window* window) {
+  windows_.insert(window);
+  window->AddObserver(this);
+}
+
+void WindowReorderer::AssociationObserver::StopObserving(
+    aura::Window* window) {
+  windows_.erase(window);
+  window->RemoveObserver(this);
+}
+
+void WindowReorderer::AssociationObserver::OnWindowPropertyChanged(
+    aura::Window* window,
+    const void* key,
+    intptr_t old) {
+  if (key == kHostViewKey)
+    reorderer_->ReorderChildWindows();
+}
+
+void WindowReorderer::AssociationObserver::OnWindowDestroying(
+    aura::Window* window) {
+  windows_.erase(window);
+  window->RemoveObserver(this);
+}
+
+WindowReorderer::WindowReorderer(aura::Window* parent_window,
+                                 View* root_view)
+    : parent_window_(parent_window),
+      root_view_(root_view),
+      association_observer_(new AssociationObserver(this)) {
+  parent_window_->AddObserver(this);
+  const std::vector<aura::Window*>& windows = parent_window_->children();
+  for (size_t i = 0; i < windows.size(); ++i)
+    association_observer_->StartObserving(windows[i]);
+  ReorderChildWindows();
+}
+
+WindowReorderer::~WindowReorderer() {
+  if (parent_window_) {
+    parent_window_->RemoveObserver(this);
+    // |association_observer_| stops observing any windows it is observing upon
+    // destruction.
+  }
+}
+
+void WindowReorderer::ReorderChildWindows() {
+  if (!parent_window_)
+    return;
+
+  std::map<View*, aura::Window*> hosted_windows;
+  GetViewsWithAssociatedWindow(*parent_window_, &hosted_windows);
+
+  if (hosted_windows.empty()) {
+    // Exit early if there are no views with associated windows.
+    // View::ReorderLayers() should have already reordered the layers owned by
+    // views.
+    return;
+  }
+
+  // Compute the desired z-order of the layers based on the order of the views
+  // with layers and views with associated windows in the view tree.
+  std::vector<View*> view_with_layer_order;
+  GetOrderOfViewsWithLayers(root_view_, parent_window_->layer(), hosted_windows,
+      &view_with_layer_order);
+
+  // For the sake of simplicity, reorder both the layers owned by views and the
+  // layers of windows associated with a view. Iterate through
+  // |view_with_layer_order| backwards and stack windows at the bottom so that
+  // windows not associated to a view are stacked above windows with an
+  // associated view.
+  for (std::vector<View*>::reverse_iterator it = view_with_layer_order.rbegin();
+       it != view_with_layer_order.rend(); ++it) {
+    View* view = *it;
+    ui::Layer* layer = view->layer();
+    aura::Window* window = NULL;
+
+    std::map<View*, aura::Window*>::iterator hosted_window_it =
+        hosted_windows.find(view);
+    if (hosted_window_it != hosted_windows.end()) {
+      window = hosted_window_it->second;
+      layer = window->layer();
+    }
+
+    DCHECK(layer);
+    if (window)
+      parent_window_->StackChildAtBottom(window);
+    parent_window_->layer()->StackAtBottom(layer);
+  }
+}
+
+void WindowReorderer::OnWindowAdded(aura::Window* new_window) {
+  association_observer_->StartObserving(new_window);
+  ReorderChildWindows();
+}
+
+void WindowReorderer::OnWillRemoveWindow(aura::Window* window) {
+  association_observer_->StopObserving(window);
+}
+
+void WindowReorderer::OnWindowDestroying(aura::Window* window) {
+  parent_window_->RemoveObserver(this);
+  parent_window_ = NULL;
+  association_observer_.reset();
+}
+
+}  // namespace views