text: // Copyright (c) 2012 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 "ash/wm/panels/panel_layout_manager.h"
  
  #include <algorithm>
  #include <map>
  
  #include "ash/launcher/launcher.h"
  #include "ash/screen_ash.h"
  #include "ash/shelf/shelf_types.h"
  #include "ash/shelf/shelf_widget.h"
  #include "ash/shell.h"
  #include "ash/wm/frame_painter.h"
  #include "ash/wm/property_util.h"
  #include "ash/wm/window_animations.h"
  #include "ash/wm/window_util.h"
  #include "base/auto_reset.h"
  #include "base/bind.h"
  #include "base/bind_helpers.h"
  #include "third_party/skia/include/core/SkColor.h"
  #include "third_party/skia/include/core/SkPaint.h"
  #include "third_party/skia/include/core/SkPath.h"
  #include "ui/aura/client/activation_client.h"
  #include "ui/aura/client/aura_constants.h"
  #include "ui/aura/focus_manager.h"
  #include "ui/aura/root_window.h"
  #include "ui/aura/window.h"
  #include "ui/compositor/scoped_layer_animation_settings.h"
  #include "ui/gfx/canvas.h"
  #include "ui/gfx/rect.h"
  #include "ui/gfx/vector2d.h"
  #include "ui/views/background.h"
  #include "ui/views/widget/widget.h"
  
  namespace ash {
  namespace internal {
  
  namespace {
  const int kPanelMarginEdge = 4;
  const int kPanelMarginMiddle = 8;
  const int kPanelIdealSpacing = 4;
  
  const float kMaxHeightFactor = .80f;
  const float kMaxWidthFactor = .50f;
  
  // Duration for panel animations.
  const int kPanelSlideDurationMilliseconds = 50;
  const int kCalloutFadeDurationMilliseconds = 50;
  
  // Offset used when sliding panel in/out of the launcher. Used for minimizing,
  // restoring and the initial showing of a panel.
  const int kPanelSlideInOffset = 20;
  
  // Callout arrow dimensions.
  const int kArrowWidth = 18;
  const int kArrowHeight = 9;
  
  class CalloutWidgetBackground : public views::Background {
   public:
    CalloutWidgetBackground() : alignment_(SHELF_ALIGNMENT_BOTTOM) {
    }
  
    virtual void Paint(gfx::Canvas* canvas, views::View* view) const OVERRIDE {
      SkPath path;
      switch (alignment_) {
        case SHELF_ALIGNMENT_BOTTOM:
          path.moveTo(SkIntToScalar(0), SkIntToScalar(0));
          path.lineTo(SkIntToScalar(kArrowWidth / 2),
                      SkIntToScalar(kArrowHeight));
          path.lineTo(SkIntToScalar(kArrowWidth), SkIntToScalar(0));
          break;
        case SHELF_ALIGNMENT_LEFT:
          path.moveTo(SkIntToScalar(kArrowHeight), SkIntToScalar(kArrowWidth));
          path.lineTo(SkIntToScalar(0), SkIntToScalar(kArrowWidth / 2));
          path.lineTo(SkIntToScalar(kArrowHeight), SkIntToScalar(0));
          break;
        case SHELF_ALIGNMENT_TOP:
          path.moveTo(SkIntToScalar(0), SkIntToScalar(kArrowHeight));
          path.lineTo(SkIntToScalar(kArrowWidth / 2), SkIntToScalar(0));
          path.lineTo(SkIntToScalar(kArrowWidth), SkIntToScalar(kArrowHeight));
          break;
        case SHELF_ALIGNMENT_RIGHT:
          path.moveTo(SkIntToScalar(0), SkIntToScalar(0));
          path.lineTo(SkIntToScalar(kArrowHeight),
                      SkIntToScalar(kArrowWidth / 2));
          path.lineTo(SkIntToScalar(0), SkIntToScalar(kArrowWidth));
          break;
      }
      // Hard code the arrow color for now.
      SkPaint paint;
      paint.setStyle(SkPaint::kFill_Style);
      paint.setColor(SkColorSetARGB(0xff, 0xe5, 0xe5, 0xe5));
      canvas->DrawPath(path, paint);
    }
  
    void set_alignment(ShelfAlignment alignment) {
      alignment_ = alignment;
    }
  
   private:
    ShelfAlignment alignment_;
  
    DISALLOW_COPY_AND_ASSIGN(CalloutWidgetBackground);
  };
  
  struct VisiblePanelPositionInfo {
    VisiblePanelPositionInfo()
        : min_major(0),
          max_major(0),
          major_pos(0),
          major_length(0),
          window(NULL),
          slide_in(false) {}
  
    int min_major;
    int max_major;
    int major_pos;
    int major_length;
    aura::Window* window;
    bool slide_in;
  };
  
  bool CompareWindowMajor(const VisiblePanelPositionInfo& win1,
                          const VisiblePanelPositionInfo& win2) {
    return win1.major_pos < win2.major_pos;
  }
  
  void FanOutPanels(std::vector<VisiblePanelPositionInfo>::iterator first,
                    std::vector<VisiblePanelPositionInfo>::iterator last) {
    int num_panels = last - first;
    if (num_panels == 1) {
      (*first).major_pos = std::max((*first).min_major, std::min(
          (*first).max_major, (*first).major_pos));
    }
    if (num_panels <= 1)
      return;
  
    if (num_panels == 2) {
      // If there are two adjacent overlapping windows, separate them by the
      // minimum major_length necessary.
      std::vector<VisiblePanelPositionInfo>::iterator second = first + 1;
      int separation = (*first).major_length / 2 + (*second).major_length / 2 +
                       kPanelIdealSpacing;
      int overlap = (*first).major_pos + separation - (*second).major_pos;
      (*first).major_pos = std::max((*first).min_major,
                                    (*first).major_pos - overlap / 2);
      (*second).major_pos = std::min((*second).max_major,
                                     (*first).major_pos + separation);
      // Recalculate the first panel position in case the second one was
      // constrained on the right.
      (*first).major_pos = std::max((*first).min_major,
                                    (*second).major_pos - separation);
      return;
    }
  
    // If there are more than two overlapping windows, fan them out from minimum
    // position to maximum position equally spaced.
    int delta = ((*(last - 1)).max_major - (*first).min_major) / (num_panels - 1);
    int major_pos = (*first).min_major;
    for (std::vector<VisiblePanelPositionInfo>::iterator iter = first;
        iter != last; ++iter) {
      (*iter).major_pos = std::max((*iter).min_major,
                                   std::min((*iter).max_major, major_pos));
      major_pos += delta;
    }
  }
  
  bool BoundsAdjacent(const gfx::Rect& bounds1, const gfx::Rect& bounds2) {
    return bounds1.x() == bounds2.right() ||
           bounds1.y() == bounds2.bottom() ||
           bounds1.right() == bounds2.x() ||
           bounds1.bottom() == bounds2.y();
  }
  
  gfx::Vector2d GetSlideInAnimationOffset(ShelfAlignment alignment) {
    gfx::Vector2d offset;
    switch (alignment) {
      case SHELF_ALIGNMENT_BOTTOM:
        offset.set_y(kPanelSlideInOffset);
        break;
      case SHELF_ALIGNMENT_LEFT:
        offset.set_x(-kPanelSlideInOffset);
        break;
      case SHELF_ALIGNMENT_RIGHT:
        offset.set_x(kPanelSlideInOffset);
        break;
      case SHELF_ALIGNMENT_TOP:
        offset.set_y(-kPanelSlideInOffset);
        break;
    }
    return offset;
  }
  
  }  // namespace
  
  class PanelCalloutWidget : public views::Widget {
   public:
    explicit PanelCalloutWidget(aura::Window* container)
        : background_(NULL) {
      InitWidget(container);
    }
  
    void SetAlignment(ShelfAlignment alignment) {
      gfx::Rect callout_bounds = GetWindowBoundsInScreen();
      if (alignment == SHELF_ALIGNMENT_BOTTOM ||
          alignment == SHELF_ALIGNMENT_TOP) {
        callout_bounds.set_width(kArrowWidth);
        callout_bounds.set_height(kArrowHeight);
      } else {
        callout_bounds.set_width(kArrowHeight);
        callout_bounds.set_height(kArrowWidth);
      }
      GetNativeWindow()->SetBounds(callout_bounds);
      background_->set_alignment(alignment);
    }
  
   private:
    void InitWidget(aura::Window* parent) {
      views::Widget::InitParams params;
      params.type = views::Widget::InitParams::TYPE_POPUP;
      params.transparent = true;
      params.can_activate = false;
      params.keep_on_top = true;
      params.ownership = views::Widget::InitParams::WIDGET_OWNS_NATIVE_WIDGET;
      params.parent = parent;
      params.bounds = ScreenAsh::ConvertRectToScreen(parent, gfx::Rect());
      params.bounds.set_width(kArrowWidth);
      params.bounds.set_height(kArrowHeight);
      // Why do we need this and can_activate = false?
      set_focus_on_creation(false);
      Init(params);
      DCHECK_EQ(GetNativeView()->GetRootWindow(), parent->GetRootWindow());
      views::View* content_view = new views::View;
      background_ = new CalloutWidgetBackground;
      content_view->set_background(background_);
      SetContentsView(content_view);
      GetNativeWindow()->layer()->SetOpacity(0);
    }
  
    // Weak pointer owned by this widget's content view.
    CalloutWidgetBackground* background_;
  
    DISALLOW_COPY_AND_ASSIGN(PanelCalloutWidget);
  };
  
  ////////////////////////////////////////////////////////////////////////////////
  // PanelLayoutManager public implementation:
  PanelLayoutManager::PanelLayoutManager(aura::Window* panel_container)
      : panel_container_(panel_container),
        in_layout_(false),
        dragged_panel_(NULL),
        launcher_(NULL),
        shelf_layout_manager_(NULL),
        shelf_hidden_(false),
        last_active_panel_(NULL),
        weak_factory_(this) {
    DCHECK(panel_container);
    aura::client::GetActivationClient(Shell::GetPrimaryRootWindow())->
        AddObserver(this);
    Shell::GetInstance()->AddShellObserver(this);
  }
  
  PanelLayoutManager::~PanelLayoutManager() {
    if (launcher_)
      launcher_->RemoveIconObserver(this);
    if (shelf_layout_manager_)
      shelf_layout_manager_->RemoveObserver(this);
    Shutdown();
    aura::client::GetActivationClient(Shell::GetPrimaryRootWindow())->
        RemoveObserver(this);
    Shell::GetInstance()->RemoveShellObserver(this);
  }
  
  void PanelLayoutManager::Shutdown() {
    for (PanelList::iterator iter = panel_windows_.begin();
         iter != panel_windows_.end(); ++iter) {
      delete iter->callout_widget;
    }
    panel_windows_.clear();
    if (launcher_)
      launcher_->RemoveIconObserver(this);
    launcher_ = NULL;
  }
  
  void PanelLayoutManager::StartDragging(aura::Window* panel) {
    DCHECK(!dragged_panel_);
    dragged_panel_ = panel;
    Relayout();
  }
  
  void PanelLayoutManager::FinishDragging() {
    dragged_panel_ = NULL;
    Relayout();
  }
  
  void PanelLayoutManager::SetLauncher(ash::Launcher* launcher) {
    DCHECK(!launcher_);
    DCHECK(!shelf_layout_manager_);
    launcher_ = launcher;
    launcher_->AddIconObserver(this);
    if (launcher_->shelf_widget()) {
      shelf_layout_manager_ = ash::internal::ShelfLayoutManager::ForLauncher(
          launcher_->shelf_widget()->GetNativeWindow());
      WillChangeVisibilityState(shelf_layout_manager_->visibility_state());
      shelf_layout_manager_->AddObserver(this);
    }
  }
  
  void PanelLayoutManager::ToggleMinimize(aura::Window* panel) {
    DCHECK(panel->parent() == panel_container_);
    if (panel->GetProperty(aura::client::kShowStateKey) ==
        ui::SHOW_STATE_MINIMIZED) {
      panel->SetProperty(aura::client::kShowStateKey, ui::SHOW_STATE_NORMAL);
    } else {
      panel->SetProperty(aura::client::kShowStateKey, ui::SHOW_STATE_MINIMIZED);
    }
  }
  
  ////////////////////////////////////////////////////////////////////////////////
  // PanelLayoutManager, aura::LayoutManager implementation:
  void PanelLayoutManager::OnWindowResized() {
    Relayout();
  }
  
  void PanelLayoutManager::OnWindowAddedToLayout(aura::Window* child) {
    if (child->type() == aura::client::WINDOW_TYPE_POPUP)
      return;
    PanelInfo panel_info;
    panel_info.window = child;
    panel_info.callout_widget = new PanelCalloutWidget(panel_container_);
    if (child != dragged_panel_) {
      // Set the panel to 0 opacity until it has been positioned to prevent it
      // from flashing briefly at position (0, 0).
      child->layer()->SetOpacity(0);
      panel_info.slide_in = true;
    }
    panel_windows_.push_back(panel_info);
    child->AddObserver(this);
    Relayout();
  }
  
  void PanelLayoutManager::OnWillRemoveWindowFromLayout(aura::Window* child) {
  }
  
  void PanelLayoutManager::OnWindowRemovedFromLayout(aura::Window* child) {
    if (child->type() == aura::client::WINDOW_TYPE_POPUP)
      return;
    PanelList::iterator found =
        std::find(panel_windows_.begin(), panel_windows_.end(), child);
    if (found != panel_windows_.end()) {
      delete found->callout_widget;
      panel_windows_.erase(found);
    }
    child->RemoveObserver(this);
  
    if (dragged_panel_ == child)
      dragged_panel_ = NULL;
  
    if (last_active_panel_ == child)
      last_active_panel_ = NULL;
  
    Relayout();
  }
  
  void PanelLayoutManager::OnChildWindowVisibilityChanged(aura::Window* child,
                                                          bool visible) {
    Relayout();
  }
  
  void PanelLayoutManager::SetChildBounds(aura::Window* child,
                                          const gfx::Rect& requested_bounds) {
    gfx::Rect bounds(requested_bounds);
    const gfx::Rect& max_bounds = panel_container_->GetRootWindow()->bounds();
    const int max_width = max_bounds.width() * kMaxWidthFactor;
    const int max_height = max_bounds.height() * kMaxHeightFactor;
    if (bounds.width() > max_width)
      bounds.set_width(max_width);
    if (bounds.height() > max_height)
      bounds.set_height(max_height);
  
    // Reposition dragged panel in the panel order.
    if (dragged_panel_ == child) {
      PanelList::iterator dragged_panel_iter =
        std::find(panel_windows_.begin(), panel_windows_.end(), dragged_panel_);
      DCHECK(dragged_panel_iter != panel_windows_.end());
      PanelList::iterator new_position;
      for (new_position = panel_windows_.begin();
           new_position != panel_windows_.end();
           ++new_position) {
        const gfx::Rect& bounds = (*new_position).window->bounds();
        if (bounds.x() + bounds.width()/2 <= requested_bounds.x()) break;
      }
      if (new_position != dragged_panel_iter) {
        PanelInfo dragged_panel_info = *dragged_panel_iter;
        panel_windows_.erase(dragged_panel_iter);
        panel_windows_.insert(new_position, dragged_panel_info);
      }
    }
  
    SetChildBoundsDirect(child, bounds);
    Relayout();
  }
  
  ////////////////////////////////////////////////////////////////////////////////
  // PanelLayoutManager, ash::LauncherIconObserver implementation:
  
  void PanelLayoutManager::OnLauncherIconPositionsChanged() {
    // TODO: As this is called for every animation step now. Relayout needs to be
    // updated to use current icon position instead of use the ideal bounds so
    // that the panels slide with their icons instead of jumping.
    Relayout();
  }
  
  ////////////////////////////////////////////////////////////////////////////////
  // PanelLayoutManager, ash::ShellObserver implementation:
  
  void PanelLayoutManager::OnShelfAlignmentChanged(
      aura::RootWindow* root_window) {
    if (panel_container_->GetRootWindow() == root_window)
      Relayout();
  }
  
  /////////////////////////////////////////////////////////////////////////////
  // PanelLayoutManager, WindowObserver implementation:
  
  void PanelLayoutManager::OnWindowPropertyChanged(aura::Window* window,
                                                   const void* key,
                                                   intptr_t old) {
    if (key != aura::client::kShowStateKey)
      return;
    // The window property will still be set, but no actual change will occur
    // until WillChangeVisibilityState is called when the shelf is visible again.
    if (shelf_hidden_)
      return;
    ui::WindowShowState new_state =
        window->GetProperty(aura::client::kShowStateKey);
    if (new_state == ui::SHOW_STATE_MINIMIZED)
      MinimizePanel(window);
    else
      RestorePanel(window);
  }
  
  void PanelLayoutManager::OnWindowVisibilityChanged(
      aura::Window* window, bool visible) {
    if (visible)
      window->SetProperty(aura::client::kShowStateKey, ui::SHOW_STATE_NORMAL);
  }
  
  ////////////////////////////////////////////////////////////////////////////////
  // PanelLayoutManager, aura::client::ActivationChangeObserver implementation:
  
  void PanelLayoutManager::OnWindowActivated(aura::Window* gained_active,
                                             aura::Window* lost_active) {
    // Ignore if the panel that is not managed by this was activated.
    if (gained_active &&
        gained_active->type() == aura::client::WINDOW_TYPE_PANEL &&
        gained_active->parent() == panel_container_) {
      UpdateStacking(gained_active);
      UpdateCallouts();
    }
  }
  
  ////////////////////////////////////////////////////////////////////////////////
  // PanelLayoutManager, ShelfLayoutManager::Observer implementation:
  
  void PanelLayoutManager::WillChangeVisibilityState(
      ShelfVisibilityState new_state) {
    // On entering / leaving full screen mode the shelf visibility state is
    // changed to / from SHELF_HIDDEN. In this state, panel windows should hide
    // to allow the full-screen application to use the full screen.
    shelf_hidden_ = new_state == ash::SHELF_HIDDEN;
    for (PanelList::iterator iter = panel_windows_.begin();
         iter != panel_windows_.end(); ++iter) {
      if (shelf_hidden_) {
        if (iter->window->IsVisible())
          MinimizePanel(iter->window);
      } else {
        if (iter->window->GetProperty(aura::client::kShowStateKey) !=
                ui::SHOW_STATE_MINIMIZED) {
          RestorePanel(iter->window);
        }
      }
    }
  }
  
  ////////////////////////////////////////////////////////////////////////////////
  // PanelLayoutManager private implementation:
  
  void PanelLayoutManager::MinimizePanel(aura::Window* panel) {
    views::corewm::SetWindowVisibilityAnimationType(
        panel, WINDOW_VISIBILITY_ANIMATION_TYPE_MINIMIZE);
    ui::Layer* layer = panel->layer();
    ui::ScopedLayerAnimationSettings panel_slide_settings(layer->GetAnimator());
    panel_slide_settings.SetPreemptionStrategy(
        ui::LayerAnimator::IMMEDIATELY_ANIMATE_TO_NEW_TARGET);
    panel_slide_settings.SetTransitionDuration(
        base::TimeDelta::FromMilliseconds(kPanelSlideDurationMilliseconds));
    gfx::Rect bounds(panel->bounds());
    bounds.Offset(GetSlideInAnimationOffset(
        launcher_->shelf_widget()->GetAlignment()));
    SetChildBoundsDirect(panel, bounds);
    panel->Hide();
    PanelList::iterator found =
        std::find(panel_windows_.begin(), panel_windows_.end(), panel);
    if (found != panel_windows_.end()) {
      layer->SetOpacity(0);
      // The next time the window is visible it should slide into place.
      found->slide_in = true;
    }
    if (wm::IsActiveWindow(panel))
      wm::DeactivateWindow(panel);
    Relayout();
  }
  
  void PanelLayoutManager::RestorePanel(aura::Window* panel) {
    panel->Show();
    Relayout();
  }
  
  void PanelLayoutManager::Relayout() {
    if (!launcher_ || !launcher_->shelf_widget())
      return;
  
    if (in_layout_)
      return;
    base::AutoReset<bool> auto_reset_in_layout(&in_layout_, true);
  
    ShelfAlignment alignment = launcher_->shelf_widget()->GetAlignment();
    bool horizontal = alignment == SHELF_ALIGNMENT_TOP ||
                      alignment == SHELF_ALIGNMENT_BOTTOM;
    gfx::Rect launcher_bounds = ash::ScreenAsh::ConvertRectFromScreen(
        panel_container_, launcher_->shelf_widget()->GetWindowBoundsInScreen());
    int panel_start_bounds = kPanelIdealSpacing;
    int panel_end_bounds = horizontal ?
        panel_container_->bounds().width() - kPanelIdealSpacing :
        panel_container_->bounds().height() - kPanelIdealSpacing;
    aura::Window* active_panel = NULL;
    std::vector<VisiblePanelPositionInfo> visible_panels;
    for (PanelList::iterator iter = panel_windows_.begin();
         iter != panel_windows_.end(); ++iter) {
      aura::Window* panel = iter->window;
      iter->callout_widget->SetAlignment(alignment);
  
      // Consider the dragged panel as part of the layout as long as it is
      // touching the launcher.
      if (!panel->IsVisible() ||
          (panel == dragged_panel_ &&
           !BoundsAdjacent(panel->bounds(), launcher_bounds))) {
        continue;
      }
  
      // If the shelf is currently hidden (full-screen mode), hide panel until
      // full-screen mode is exited.
      if (shelf_hidden_) {
        // The call to Hide does not set the minimize property, so the window will
        // be restored when the shelf becomes visible again.
        panel->Hide();
        continue;
      }
  
      gfx::Rect icon_bounds =
          launcher_->GetScreenBoundsOfItemIconForWindow(panel);
  
      // If both the icon width and height are 0 then there is no icon in the
      // launcher. If the launcher is hidden, one of the height or width will be
      // 0 but the position in the launcher and major dimension is still reported
      // correctly and the panel can be aligned above where the hidden icon is.
      if (icon_bounds.width() == 0 && icon_bounds.height() == 0)
        continue;
  
      if (panel->HasFocus() ||
          panel->Contains(
              aura::client::GetFocusClient(panel)->GetFocusedWindow())) {
        DCHECK(!active_panel);
        active_panel = panel;
      }
      icon_bounds = ScreenAsh::ConvertRectFromScreen(panel_container_,
                                                     icon_bounds);
      gfx::Point icon_origin = icon_bounds.origin();
      VisiblePanelPositionInfo position_info;
      int icon_start = horizontal ? icon_origin.x() : icon_origin.y();
      int icon_end = icon_start + (horizontal ? icon_bounds.width() :
                                   icon_bounds.height());
      position_info.major_length = horizontal ?
          panel->bounds().width() : panel->bounds().height();
      position_info.min_major = std::max(
          panel_start_bounds + position_info.major_length / 2,
          icon_end - position_info.major_length / 2);
      position_info.max_major = std::min(
          icon_start + position_info.major_length / 2,
          panel_end_bounds - position_info.major_length / 2);
      position_info.major_pos = (icon_start + icon_end) / 2;
      position_info.window = panel;
      position_info.slide_in = iter->slide_in;
      iter->slide_in = false;
      visible_panels.push_back(position_info);
    }
  
    // Sort panels by their X positions and fan out groups of overlapping panels.
    // The fan out method may result in new overlapping panels however given that
    // the panels start at least a full panel width apart this overlap will
    // never completely obscure a panel.
    // TODO(flackr): Rearrange panels if new overlaps are introduced.
    std::sort(visible_panels.begin(), visible_panels.end(), CompareWindowMajor);
    size_t first_overlapping_panel = 0;
    for (size_t i = 1; i < visible_panels.size(); ++i) {
      if (visible_panels[i - 1].major_pos +
          visible_panels[i - 1].major_length / 2 < visible_panels[i].major_pos -
          visible_panels[i].major_length / 2) {
        FanOutPanels(visible_panels.begin() + first_overlapping_panel,
                     visible_panels.begin() + i);
        first_overlapping_panel = i;
      }
    }
    FanOutPanels(visible_panels.begin() + first_overlapping_panel,
                 visible_panels.end());
  
    for (size_t i = 0; i < visible_panels.size(); ++i) {
      if (visible_panels[i].window == dragged_panel_)
        continue;
      bool slide_in = visible_panels[i].slide_in;
      gfx::Rect bounds = visible_panels[i].window->GetTargetBounds();
      switch (alignment) {
        case SHELF_ALIGNMENT_BOTTOM:
          bounds.set_y(launcher_bounds.y() - bounds.height());
          break;
        case SHELF_ALIGNMENT_LEFT:
          bounds.set_x(launcher_bounds.right());
          break;
        case SHELF_ALIGNMENT_RIGHT:
          bounds.set_x(launcher_bounds.x() - bounds.width());
          break;
        case SHELF_ALIGNMENT_TOP:
          bounds.set_y(launcher_bounds.bottom());
          break;
      }
      bool on_launcher = visible_panels[i].window->GetTargetBounds() == bounds;
  
      if (horizontal) {
        bounds.set_x(visible_panels[i].major_pos -
                     visible_panels[i].major_length / 2);
      } else {
        bounds.set_y(visible_panels[i].major_pos -
                     visible_panels[i].major_length / 2);
      }
  
      ui::Layer* layer = visible_panels[i].window->layer();
      if (slide_in) {
        // New windows shift up from the launcher  into position.
        gfx::Rect initial_bounds(bounds);
        initial_bounds.Offset(GetSlideInAnimationOffset(alignment));
        SetChildBoundsDirect(visible_panels[i].window, initial_bounds);
        // Set on launcher so that the panel animates into its target position.
        on_launcher = true;
      }
  
      if (on_launcher) {
        ui::ScopedLayerAnimationSettings panel_slide_settings(
            layer->GetAnimator());
        panel_slide_settings.SetPreemptionStrategy(
            ui::LayerAnimator::IMMEDIATELY_ANIMATE_TO_NEW_TARGET);
        panel_slide_settings.SetTransitionDuration(
            base::TimeDelta::FromMilliseconds(kPanelSlideDurationMilliseconds));
        SetChildBoundsDirect(visible_panels[i].window, bounds);
        if (slide_in)
          layer->SetOpacity(1);
      } else {
        // If the launcher moved don't animate, move immediately to the new
        // target location.
        SetChildBoundsDirect(visible_panels[i].window, bounds);
      }
    }
  
    UpdateStacking(active_panel);
    UpdateCallouts();
  }
  
  void PanelLayoutManager::UpdateStacking(aura::Window* active_panel) {
    if (!active_panel) {
      if (!last_active_panel_)
        return;
      active_panel = last_active_panel_;
    }
  
    // We want to to stack the panels like a deck of cards:
    // ,--,--,--,-------.--.--.
    // |  |  |  |       |  |  |
    // |  |  |  |       |  |  |
    //
    // We use the middle of each panel to figure out how to stack the panels. This
    // allows us to update the stacking when a panel is being dragged around by
    // the titlebar--even though it doesn't update the launcher icon positions, we
    // still want the visual effect.
    std::map<int, aura::Window*> window_ordering;
    for (PanelList::const_iterator it = panel_windows_.begin();
         it != panel_windows_.end(); ++it) {
      gfx::Rect bounds = it->window->bounds();
      window_ordering.insert(std::make_pair(bounds.x() + bounds.width() / 2,
                                            it->window));
    }
  
    aura::Window* previous_panel = NULL;
    for (std::map<int, aura::Window*>::const_iterator it =
         window_ordering.begin();
         it != window_ordering.end() && it->second != active_panel; ++it) {
      if (previous_panel)
        panel_container_->StackChildAbove(it->second, previous_panel);
      previous_panel = it->second;
    }
  
    previous_panel = NULL;
    for (std::map<int, aura::Window*>::const_reverse_iterator it =
         window_ordering.rbegin();
         it != window_ordering.rend() && it->second != active_panel; ++it) {
      if (previous_panel)
        panel_container_->StackChildAbove(it->second, previous_panel);
      previous_panel = it->second;
    }
  
    panel_container_->StackChildAtTop(active_panel);
    if (dragged_panel_ && dragged_panel_->parent() == panel_container_)
      panel_container_->StackChildAtTop(dragged_panel_);
    last_active_panel_ = active_panel;
  }
  
  void PanelLayoutManager::UpdateCallouts() {
    ShelfAlignment alignment = launcher_->alignment();
    bool horizontal = alignment == SHELF_ALIGNMENT_TOP ||
                      alignment == SHELF_ALIGNMENT_BOTTOM;
  
    for (PanelList::iterator iter = panel_windows_.begin();
         iter != panel_windows_.end(); ++iter) {
      aura::Window* panel = iter->window;
      views::Widget* callout_widget = iter->callout_widget;
  
      gfx::Rect current_bounds = panel->GetBoundsInScreen();
      gfx::Rect bounds = ScreenAsh::ConvertRectToScreen(panel->parent(),
                                                        panel->GetTargetBounds());
      gfx::Rect icon_bounds =
          launcher_->GetScreenBoundsOfItemIconForWindow(panel);
      if (icon_bounds.IsEmpty() || !panel->layer()->GetTargetVisibility() ||
          panel == dragged_panel_) {
        callout_widget->Hide();
        callout_widget->GetNativeWindow()->layer()->SetOpacity(0);
        continue;
      }
  
      gfx::Rect callout_bounds = callout_widget->GetWindowBoundsInScreen();
      gfx::Vector2d slide_vector = bounds.origin() - current_bounds.origin();
      int slide_distance = horizontal ? slide_vector.x() : slide_vector.y();
      int distance_until_over_panel = 0;
      if (horizontal) {
        callout_bounds.set_x(
            icon_bounds.x() + (icon_bounds.width() - callout_bounds.width()) / 2);
        distance_until_over_panel = std::max(
            current_bounds.x() - callout_bounds.x(),
            callout_bounds.right() - current_bounds.right());
      } else {
        callout_bounds.set_y(
            icon_bounds.y() + (icon_bounds.height() -
                               callout_bounds.height()) / 2);
        distance_until_over_panel = std::max(
            current_bounds.y() - callout_bounds.y(),
            callout_bounds.bottom() - current_bounds.bottom());
      }
      switch (alignment) {
        case SHELF_ALIGNMENT_BOTTOM:
          callout_bounds.set_y(bounds.bottom());
          break;
        case SHELF_ALIGNMENT_LEFT:
          callout_bounds.set_x(bounds.x() - callout_bounds.width());
          break;
        case SHELF_ALIGNMENT_RIGHT:
          callout_bounds.set_x(bounds.right());
          break;
        case SHELF_ALIGNMENT_TOP:
          callout_bounds.set_y(bounds.y() - callout_bounds.height());
          break;
      }
      callout_bounds = ScreenAsh::ConvertRectFromScreen(
          callout_widget->GetNativeWindow()->parent(),
          callout_bounds);
  
      SetChildBoundsDirect(callout_widget->GetNativeWindow(), callout_bounds);
      panel_container_->StackChildAbove(callout_widget->GetNativeWindow(),
                                        panel);
      callout_widget->Show();
  
      ui::Layer* layer = callout_widget->GetNativeWindow()->layer();
      // If the panel is not over the callout position or has just become visible
      // then fade in the callout.
      if (distance_until_over_panel > 0 || layer->GetTargetOpacity() < 1) {
        if (distance_until_over_panel > 0 &&
            slide_distance >= distance_until_over_panel) {
          layer->SetOpacity(0);
          // If the panel is not yet over the callout, then delay fading in
          // the callout until after the panel should be over it.
          int delay = kPanelSlideDurationMilliseconds *
              distance_until_over_panel / slide_distance;
          layer->SetOpacity(0);
          layer->GetAnimator()->StopAnimating();
          layer->GetAnimator()->SchedulePauseForProperties(
              base::TimeDelta::FromMilliseconds(delay),
              ui::LayerAnimationElement::OPACITY);
        }
        {
          ui::ScopedLayerAnimationSettings callout_settings(layer->GetAnimator());
          callout_settings.SetPreemptionStrategy(
              ui::LayerAnimator::REPLACE_QUEUED_ANIMATIONS);
          callout_settings.SetTransitionDuration(
              base::TimeDelta::FromMilliseconds(
                  kCalloutFadeDurationMilliseconds));
          layer->SetOpacity(1);
        }
      }
    }
  }
  
  ////////////////////////////////////////////////////////////////////////////////
  // keyboard::KeyboardControllerObserver implementation:
  
  void PanelLayoutManager::OnKeyboardBoundsChanging(
      const gfx::Rect& keyboard_bounds) {
    // This bounds change will have caused a change to the Shelf which does not
    // propogate automatically to this class, so manually recalculate bounds.
    OnWindowResized();
  }
  
  }  // namespace internal
  }  // namespace ash
  