views/tabs/tab_strip.cc

// Copyright (c) 2011 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 "chrome/browser/ui/views/tabs/tab_strip.h"

#include <algorithm>

#include "base/compiler_specific.h"
#include "base/stl_util-inl.h"
#include "base/utf_string_conversions.h"
#include "chrome/browser/defaults.h"
#include "chrome/browser/themes/theme_service.h"
#include "chrome/browser/ui/view_ids.h"
#include "chrome/browser/ui/views/tabs/tab.h"
#include "chrome/browser/ui/views/tabs/tab_strip_controller.h"
#include "grit/generated_resources.h"
#include "grit/theme_resources.h"
#include "ui/base/accessibility/accessible_view_state.h"
#include "ui/base/animation/animation_container.h"
#include "ui/base/dragdrop/drag_drop_types.h"
#include "ui/base/l10n/l10n_util.h"
#include "ui/base/resource/resource_bundle.h"
#include "ui/gfx/canvas_skia.h"
#include "ui/gfx/path.h"
#include "ui/gfx/size.h"
#include "views/controls/image_view.h"
#include "views/widget/default_theme_provider.h"
#include "views/window/non_client_view.h"
#include "views/window/window.h"

#if defined(OS_WIN)
#include "views/widget/monitor_win.h"
#include "views/widget/widget_win.h"
#elif defined(OS_LINUX)
#include "views/widget/widget_gtk.h"
#endif

#undef min
#undef max

#if defined(COMPILER_GCC)
// Squash false positive signed overflow warning in GenerateStartAndEndWidths
// when doing 'start_tab_count < end_tab_count'.
#pragma GCC diagnostic ignored "-Wstrict-overflow"
#endif

using views::DropTargetEvent;

static const int kNewTabButtonHOffset = -5;
static const int kNewTabButtonVOffset = 5;
static const int kSuspendAnimationsTimeMs = 200;
static const int kTabHOffset = -16;
static const int kTabStripAnimationVSlop = 40;

// Size of the drop indicator.
static int drop_indicator_width;
static int drop_indicator_height;

static inline int Round(double x) {
  // Why oh why is this not in a standard header?
  return static_cast<int>(floor(x + 0.5));
}

namespace {

///////////////////////////////////////////////////////////////////////////////
// NewTabButton
//
//  A subclass of button that hit-tests to the shape of the new tab button.

class NewTabButton : public views::ImageButton {
 public:
  explicit NewTabButton(views::ButtonListener* listener)
      : views::ImageButton(listener) {
  }
  virtual ~NewTabButton() {}

 protected:
  // Overridden from views::View:
  virtual bool HasHitTestMask() const {
    // When the button is sized to the top of the tab strip we want the user to
    // be able to click on complete bounds, and so don't return a custom hit
    // mask.
    return !browser_defaults::kSizeTabButtonToTopOfTabStrip;
  }
  virtual void GetHitTestMask(gfx::Path* path) const {
    DCHECK(path);

    SkScalar w = SkIntToScalar(width());

    // These values are defined by the shape of the new tab bitmap. Should that
    // bitmap ever change, these values will need to be updated. They're so
    // custom it's not really worth defining constants for.
    path->moveTo(0, 1);
    path->lineTo(w - 7, 1);
    path->lineTo(w - 4, 4);
    path->lineTo(w, 16);
    path->lineTo(w - 1, 17);
    path->lineTo(7, 17);
    path->lineTo(4, 13);
    path->lineTo(0, 1);
    path->close();
  }

 private:
  DISALLOW_COPY_AND_ASSIGN(NewTabButton);
};

}  // namespace

///////////////////////////////////////////////////////////////////////////////
// TabStrip, public:

// static
const int TabStrip::mini_to_non_mini_gap_ = 3;

TabStrip::TabStrip(TabStripController* controller)
    : BaseTabStrip(controller, BaseTabStrip::HORIZONTAL_TAB_STRIP),
      newtab_button_(NULL),
      current_unselected_width_(Tab::GetStandardSize().width()),
      current_selected_width_(Tab::GetStandardSize().width()),
      available_width_for_tabs_(-1),
      in_tab_close_(false),
      animation_container_(new ui::AnimationContainer()) {
  Init();
}

TabStrip::~TabStrip() {
  // The animations may reference the tabs. Shut down the animation before we
  // delete the tabs.
  StopAnimating(false);

  DestroyDragController();

  // Make sure we unhook ourselves as a message loop observer so that we don't
  // crash in the case where the user closes the window after closing a tab
  // but before moving the mouse.
  RemoveMessageLoopObserver();

  // The children (tabs) may callback to us from their destructor. Delete them
  // so that if they call back we aren't in a weird state.
  RemoveAllChildViews(true);
}

void TabStrip::InitTabStripButtons() {
  newtab_button_ = new NewTabButton(this);
  if (browser_defaults::kSizeTabButtonToTopOfTabStrip) {
    newtab_button_->SetImageAlignment(views::ImageButton::ALIGN_LEFT,
                                      views::ImageButton::ALIGN_BOTTOM);
  }
  LoadNewTabButtonImage();
  newtab_button_->SetAccessibleName(
      l10n_util::GetStringUTF16(IDS_ACCNAME_NEWTAB));
  AddChildView(newtab_button_);
}

gfx::Rect TabStrip::GetNewTabButtonBounds() {
  return newtab_button_->bounds();
}

void TabStrip::MouseMovedOutOfView() {
  ResizeLayoutTabs();
}

////////////////////////////////////////////////////////////////////////////////
// TabStrip, AbstractTabStripView implementation:

bool TabStrip::IsPositionInWindowCaption(const gfx::Point& point) {
  views::View* v = GetEventHandlerForPoint(point);

  // If there is no control at this location, claim the hit was in the title
  // bar to get a move action.
  if (v == this)
    return true;

  // Check to see if the point is within the non-button parts of the new tab
  // button. The button has a non-rectangular shape, so if it's not in the
  // visual portions of the button we treat it as a click to the caption.
  gfx::Point point_in_newtab_coords(point);
  View::ConvertPointToView(this, newtab_button_, &point_in_newtab_coords);
  if (newtab_button_->bounds().Contains(point) &&
      !newtab_button_->HitTest(point_in_newtab_coords)) {
    return true;
  }

  // All other regions, including the new Tab button, should be considered part
  // of the containing Window's client area so that regular events can be
  // processed for them.
  return false;
}

void TabStrip::SetBackgroundOffset(const gfx::Point& offset) {
  for (int i = 0; i < tab_count(); ++i)
    GetTabAtTabDataIndex(i)->set_background_offset(offset);
}

////////////////////////////////////////////////////////////////////////////////
// TabStrip, BaseTabStrip implementation:

void TabStrip::PrepareForCloseAt(int model_index) {
  if (!in_tab_close_ && IsAnimating()) {
    // Cancel any current animations. We do this as remove uses the current
    // ideal bounds and we need to know ideal bounds is in a good state.
    StopAnimating(true);
  }

  int model_count = GetModelCount();
  if (model_index + 1 != model_count && model_count > 1) {
    // The user is about to close a tab other than the last tab. Set
    // available_width_for_tabs_ so that if we do a layout we don't position a
    // tab past the end of the second to last tab. We do this so that as the
    // user closes tabs with the mouse a tab continues to fall under the mouse.
    available_width_for_tabs_ = GetAvailableWidthForTabs(
        GetTabAtModelIndex(model_count - 2));
  }

  in_tab_close_ = true;
  AddMessageLoopObserver();
}

void TabStrip::RemoveTabAt(int model_index) {
  if (in_tab_close_ && model_index != GetModelCount())
    StartMouseInitiatedRemoveTabAnimation(model_index);
  else
    StartRemoveTabAnimation(model_index);
}

void TabStrip::SelectTabAt(int old_model_index, int new_model_index) {
  // We have "tiny tabs" if the tabs are so tiny that the unselected ones are
  // a different size to the selected ones.
  bool tiny_tabs = current_unselected_width_ != current_selected_width_;
  if (!IsAnimating() && (!in_tab_close_ || tiny_tabs)) {
    DoLayout();
  } else {
    SchedulePaint();
  }

  if (old_model_index >= 0) {
    GetTabAtTabDataIndex(ModelIndexToTabIndex(old_model_index))->
        StopMiniTabTitleAnimation();
  }
}

void TabStrip::TabTitleChangedNotLoading(int model_index) {
  Tab* tab = GetTabAtModelIndex(model_index);
  if (tab->data().mini && !tab->IsActive())
    tab->StartMiniTabTitleAnimation();
}

void TabStrip::StartHighlight(int model_index) {
  GetTabAtModelIndex(model_index)->StartPulse();
}

void TabStrip::StopAllHighlighting() {
  for (int i = 0; i < tab_count(); ++i)
    GetTabAtTabDataIndex(i)->StopPulse();
}

BaseTab* TabStrip::CreateTabForDragging() {
  Tab* tab = new Tab(NULL);
  // Make sure the dragged tab shares our theme provider. We need to explicitly
  // do this as during dragging there isn't a theme provider.
  tab->set_theme_provider(GetThemeProvider());
  return tab;
}

///////////////////////////////////////////////////////////////////////////////
// TabStrip, views::View overrides:

void TabStrip::PaintChildren(gfx::Canvas* canvas) {
  // Tabs are painted in reverse order, so they stack to the left.
  Tab* active_tab = NULL;
  std::vector<Tab*> tabs_dragging;
  std::vector<Tab*> selected_tabs;
  bool is_dragging = false;

  for (int i = tab_count() - 1; i >= 0; --i) {
    // We must ask the _Tab's_ model, not ourselves, because in some situations
    // the model will be different to this object, e.g. when a Tab is being
    // removed after its TabContents has been destroyed.
    Tab* tab = GetTabAtTabDataIndex(i);
    if (tab->dragging()) {
      is_dragging = true;
      if (tab->IsActive())
        active_tab = tab;
      else
        tabs_dragging.push_back(tab);
    } else if (!tab->IsActive()) {
      if (!tab->IsSelected())
        tab->Paint(canvas);
      else
        selected_tabs.push_back(tab);
    } else {
      active_tab = tab;
    }
  }

  if (GetWindow()->non_client_view()->UseNativeFrame()) {
    bool multiple_tabs_selected = (!selected_tabs.empty() ||
                                   tabs_dragging.size() > 1);
    // Make sure non-active tabs are somewhat transparent.
    SkPaint paint;
    // If there are multiple tabs selected, fade non-selected tabs more to make
    // the selected tabs more noticable.
    paint.setColor(SkColorSetARGB(
                       multiple_tabs_selected ? 150 : 200, 255, 255, 255));
    paint.setXfermodeMode(SkXfermode::kDstIn_Mode);
    paint.setStyle(SkPaint::kFill_Style);
    canvas->DrawRectInt(0, 0, width(),
        height() - 2,  // Visible region that overlaps the toolbar.
        paint);
  }

  // Now selected but not active. We don't want these dimmed if using native
  // frame, so they're painted after initial pass.
  for (size_t i = 0; i < selected_tabs.size(); ++i)
    selected_tabs[i]->Paint(canvas);

  // Next comes the active tab.
  if (active_tab && !is_dragging)
    active_tab->Paint(canvas);

  // Paint the New Tab button.
  newtab_button_->Paint(canvas);

  // And the dragged tabs.
  for (size_t i = 0; i < tabs_dragging.size(); ++i)
    tabs_dragging[i]->Paint(canvas);

  // If the active tab is being dragged, it goes last.
  if (active_tab && is_dragging)
    active_tab->Paint(canvas);
}

// Overridden to support automation. See automation_proxy_uitest.cc.
const views::View* TabStrip::GetViewByID(int view_id) const {
  if (tab_count() > 0) {
    if (view_id == VIEW_ID_TAB_LAST) {
      return GetTabAtTabDataIndex(tab_count() - 1);
    } else if ((view_id >= VIEW_ID_TAB_0) && (view_id < VIEW_ID_TAB_LAST)) {
      int index = view_id - VIEW_ID_TAB_0;
      if (index >= 0 && index < tab_count()) {
        return GetTabAtTabDataIndex(index);
      } else {
        return NULL;
      }
    }
  }

  return View::GetViewByID(view_id);
}

gfx::Size TabStrip::GetPreferredSize() {
  return gfx::Size(0, Tab::GetMinimumUnselectedSize().height());
}

void TabStrip::OnDragEntered(const DropTargetEvent& event) {
  // Force animations to stop, otherwise it makes the index calculation tricky.
  StopAnimating(true);

  UpdateDropIndex(event);
}

int TabStrip::OnDragUpdated(const DropTargetEvent& event) {
  UpdateDropIndex(event);
  return GetDropEffect(event);
}

void TabStrip::OnDragExited() {
  SetDropIndex(-1, false);
}

int TabStrip::OnPerformDrop(const DropTargetEvent& event) {
  if (!drop_info_.get())
    return ui::DragDropTypes::DRAG_NONE;

  const int drop_index = drop_info_->drop_index;
  const bool drop_before = drop_info_->drop_before;

  // Hide the drop indicator.
  SetDropIndex(-1, false);

  GURL url;
  string16 title;
  if (!event.data().GetURLAndTitle(&url, &title) || !url.is_valid())
    return ui::DragDropTypes::DRAG_NONE;

  controller()->PerformDrop(drop_before, drop_index, url);

  return GetDropEffect(event);
}

void TabStrip::GetAccessibleState(ui::AccessibleViewState* state) {
  state->role = ui::AccessibilityTypes::ROLE_PAGETABLIST;
}

views::View* TabStrip::GetEventHandlerForPoint(const gfx::Point& point) {
  // Return any view that isn't a Tab or this TabStrip immediately. We don't
  // want to interfere.
  views::View* v = View::GetEventHandlerForPoint(point);
  if (v && v != this && v->GetClassName() != Tab::kViewClassName)
    return v;

  // The display order doesn't necessarily match the child list order, so we
  // walk the display list hit-testing Tabs. Since the active tab always
  // renders on top of adjacent tabs, it needs to be hit-tested before any
  // left-adjacent Tab, so we look ahead for it as we walk.
  for (int i = 0; i < tab_count(); ++i) {
    Tab* next_tab = i < (tab_count() - 1) ? GetTabAtTabDataIndex(i + 1) : NULL;
    if (next_tab && next_tab->IsActive() && IsPointInTab(next_tab, point))
      return next_tab;
    Tab* tab = GetTabAtTabDataIndex(i);
    if (IsPointInTab(tab, point))
      return tab;
  }

  // No need to do any floating view stuff, we don't use them in the TabStrip.
  return this;
}

void TabStrip::OnThemeChanged() {
  LoadNewTabButtonImage();
}

BaseTab* TabStrip::CreateTab() {
  Tab* tab = new Tab(this);
  tab->set_animation_container(animation_container_.get());
  return tab;
}

void TabStrip::StartInsertTabAnimation(int model_index) {
  PrepareForAnimation();

  // The TabStrip can now use its entire width to lay out Tabs.
  in_tab_close_ = false;
  available_width_for_tabs_ = -1;

  GenerateIdealBounds();

  int tab_data_index = ModelIndexToTabIndex(model_index);
  BaseTab* tab = base_tab_at_tab_index(tab_data_index);
  if (model_index == 0) {
    tab->SetBounds(0, ideal_bounds(tab_data_index).y(), 0,
                   ideal_bounds(tab_data_index).height());
  } else {
    BaseTab* last_tab = base_tab_at_tab_index(tab_data_index - 1);
    tab->SetBounds(last_tab->bounds().right() + kTabHOffset,
                   ideal_bounds(tab_data_index).y(), 0,
                   ideal_bounds(tab_data_index).height());
  }

  AnimateToIdealBounds();
}

void TabStrip::AnimateToIdealBounds() {
  for (int i = 0; i < tab_count(); ++i) {
    Tab* tab = GetTabAtTabDataIndex(i);
    if (!tab->closing() && !tab->dragging())
      bounds_animator().AnimateViewTo(tab, ideal_bounds(i));
  }

  bounds_animator().AnimateViewTo(newtab_button_, newtab_button_bounds_);
}

bool TabStrip::ShouldHighlightCloseButtonAfterRemove() {
  return in_tab_close_;
}

void TabStrip::DoLayout() {
  BaseTabStrip::DoLayout();

  newtab_button_->SetBoundsRect(newtab_button_bounds_);
}

void TabStrip::LayoutDraggedTabsAt(const std::vector<BaseTab*>& tabs,
                                   BaseTab* active_tab,
                                   const gfx::Point& location,
                                   bool initial_drag) {
  std::vector<gfx::Rect> bounds;
  CalculateBoundsForDraggedTabs(tabs, &bounds);
  DCHECK_EQ(tabs.size(), bounds.size());
  int active_tab_model_index = GetModelIndexOfBaseTab(active_tab);
  int active_tab_index = static_cast<int>(
      std::find(tabs.begin(), tabs.end(), active_tab) - tabs.begin());
  for (size_t i = 0; i < tabs.size(); ++i) {
    BaseTab* tab = tabs[i];
    gfx::Rect new_bounds = bounds[i];
    new_bounds.Offset(location.x(), location.y());
    int consecutive_index =
        active_tab_model_index - (active_tab_index - static_cast<int>(i));
    // If this is the initial layout during a drag and the tabs aren't
    // consecutive animate the view into position. Do the same if the tab is
    // already animating (which means we previously caused it to animate).
    if ((initial_drag &&
         GetModelIndexOfBaseTab(tabs[i]) != consecutive_index) ||
        bounds_animator().IsAnimating(tabs[i])) {
      bounds_animator().SetTargetBounds(tabs[i], new_bounds);
    } else {
      tab->SetBoundsRect(new_bounds);
    }
  }
}

void TabStrip::CalculateBoundsForDraggedTabs(const std::vector<BaseTab*>& tabs,
                                             std::vector<gfx::Rect>* bounds) {
  int x = 0;
  for (size_t i = 0; i < tabs.size(); ++i) {
    BaseTab* tab = tabs[i];
    if (i > 0 && tab->data().mini != tabs[i - 1]->data().mini)
      x += mini_to_non_mini_gap_;
    gfx::Rect new_bounds = tab->bounds();
    new_bounds.set_origin(gfx::Point(x, 0));
    bounds->push_back(new_bounds);
    x += tab->width() + kTabHOffset;
  }
}

int TabStrip::GetSizeNeededForTabs(const std::vector<BaseTab*>& tabs) {
  int width = 0;
  for (size_t i = 0; i < tabs.size(); ++i) {
    BaseTab* tab = tabs[i];
    width += tab->width();
    if (i > 0 && tab->data().mini != tabs[i - 1]->data().mini)
      width += mini_to_non_mini_gap_;
  }
  if (tabs.size() > 0)
    width += kTabHOffset * static_cast<int>(tabs.size() - 1);
  return width;
}

void TabStrip::ViewHierarchyChanged(bool is_add,
                                    views::View* parent,
                                    views::View* child) {
  if (is_add && child == this)
    InitTabStripButtons();
}

///////////////////////////////////////////////////////////////////////////////
// TabStrip, views::BaseButton::ButtonListener implementation:

void TabStrip::ButtonPressed(views::Button* sender, const views::Event& event) {
  if (sender == newtab_button_)
    controller()->CreateNewTab();
}

///////////////////////////////////////////////////////////////////////////////
// TabStrip, private:

void TabStrip::Init() {
  SetID(VIEW_ID_TAB_STRIP);
  newtab_button_bounds_.SetRect(0, 0, kNewTabButtonWidth, kNewTabButtonHeight);
  if (browser_defaults::kSizeTabButtonToTopOfTabStrip) {
    newtab_button_bounds_.set_height(
        kNewTabButtonHeight + kNewTabButtonVOffset);
  }
  if (drop_indicator_width == 0) {
    // Direction doesn't matter, both images are the same size.
    SkBitmap* drop_image = GetDropArrowImage(true);
    drop_indicator_width = drop_image->width();
    drop_indicator_height = drop_image->height();
  }
}

void TabStrip::LoadNewTabButtonImage() {
  ui::ThemeProvider* tp = GetThemeProvider();

  // If we don't have a theme provider yet, it means we do not have a
  // root view, and are therefore in a test.
  bool in_test = false;
  if (tp == NULL) {
    tp = new views::DefaultThemeProvider();
    in_test = true;
  }

  SkBitmap* bitmap = tp->GetBitmapNamed(IDR_NEWTAB_BUTTON);
  SkColor color = tp->GetColor(ThemeService::COLOR_BUTTON_BACKGROUND);
  SkBitmap* background = tp->GetBitmapNamed(
      IDR_THEME_WINDOW_CONTROL_BACKGROUND);

  newtab_button_->SetImage(views::CustomButton::BS_NORMAL, bitmap);
  newtab_button_->SetImage(views::CustomButton::BS_PUSHED,
                           tp->GetBitmapNamed(IDR_NEWTAB_BUTTON_P));
  newtab_button_->SetImage(views::CustomButton::BS_HOT,
                           tp->GetBitmapNamed(IDR_NEWTAB_BUTTON_H));
  newtab_button_->SetBackground(color, background,
                                tp->GetBitmapNamed(IDR_NEWTAB_BUTTON_MASK));
  if (in_test)
    delete tp;
}

Tab* TabStrip::GetTabAtTabDataIndex(int tab_data_index) const {
  return static_cast<Tab*>(base_tab_at_tab_index(tab_data_index));
}

Tab* TabStrip::GetTabAtModelIndex(int model_index) const {
  return GetTabAtTabDataIndex(ModelIndexToTabIndex(model_index));
}

void TabStrip::GetCurrentTabWidths(double* unselected_width,
                                   double* selected_width) const {
  *unselected_width = current_unselected_width_;
  *selected_width = current_selected_width_;
}

void TabStrip::GetDesiredTabWidths(int tab_count,
                                   int mini_tab_count,
                                   double* unselected_width,
                                   double* selected_width) const {
  DCHECK(tab_count >= 0 && mini_tab_count >= 0 && mini_tab_count <= tab_count);
  const double min_unselected_width = Tab::GetMinimumUnselectedSize().width();
  const double min_selected_width = Tab::GetMinimumSelectedSize().width();

  *unselected_width = min_unselected_width;
  *selected_width = min_selected_width;

  if (tab_count == 0) {
    // Return immediately to avoid divide-by-zero below.
    return;
  }

  // Determine how much space we can actually allocate to tabs.
  int available_width;
  if (available_width_for_tabs_ < 0) {
    available_width = width();
    available_width -= (kNewTabButtonHOffset + newtab_button_bounds_.width());
  } else {
    // Interesting corner case: if |available_width_for_tabs_| > the result
    // of the calculation in the conditional arm above, the strip is in
    // overflow.  We can either use the specified width or the true available
    // width here; the first preserves the consistent "leave the last tab under
    // the user's mouse so they can close many tabs" behavior at the cost of
    // prolonging the glitchy appearance of the overflow state, while the second
    // gets us out of overflow as soon as possible but forces the user to move
    // their mouse for a few tabs' worth of closing.  We choose visual
    // imperfection over behavioral imperfection and select the first option.
    available_width = available_width_for_tabs_;
  }

  if (mini_tab_count > 0) {
    available_width -= mini_tab_count * (Tab::GetMiniWidth() + kTabHOffset);
    tab_count -= mini_tab_count;
    if (tab_count == 0) {
      *selected_width = *unselected_width = Tab::GetStandardSize().width();
      return;
    }
    // Account for gap between the last mini-tab and first non-mini-tab.
    available_width -= mini_to_non_mini_gap_;
  }

  // Calculate the desired tab widths by dividing the available space into equal
  // portions.  Don't let tabs get larger than the "standard width" or smaller
  // than the minimum width for each type, respectively.
  const int total_offset = kTabHOffset * (tab_count - 1);
  const double desired_tab_width = std::min((static_cast<double>(
      available_width - total_offset) / static_cast<double>(tab_count)),
      static_cast<double>(Tab::GetStandardSize().width()));
  *unselected_width = std::max(desired_tab_width, min_unselected_width);
  *selected_width = std::max(desired_tab_width, min_selected_width);

  // When there are multiple tabs, we'll have one selected and some unselected
  // tabs.  If the desired width was between the minimum sizes of these types,
  // try to shrink the tabs with the smaller minimum.  For example, if we have
  // a strip of width 10 with 4 tabs, the desired width per tab will be 2.5.  If
  // selected tabs have a minimum width of 4 and unselected tabs have a minimum
  // width of 1, the above code would set *unselected_width = 2.5,
  // *selected_width = 4, which results in a total width of 11.5.  Instead, we
  // want to set *unselected_width = 2, *selected_width = 4, for a total width
  // of 10.
  if (tab_count > 1) {
    if ((min_unselected_width < min_selected_width) &&
        (desired_tab_width < min_selected_width)) {
      // Unselected width = (total width - selected width) / (num_tabs - 1)
      *unselected_width = std::max(static_cast<double>(
          available_width - total_offset - min_selected_width) /
          static_cast<double>(tab_count - 1), min_unselected_width);
    } else if ((min_unselected_width > min_selected_width) &&
               (desired_tab_width < min_unselected_width)) {
      // Selected width = (total width - (unselected width * (num_tabs - 1)))
      *selected_width = std::max(available_width - total_offset -
          (min_unselected_width * (tab_count - 1)), min_selected_width);
    }
  }
}

void TabStrip::ResizeLayoutTabs() {
  // We've been called back after the TabStrip has been emptied out (probably
  // just prior to the window being destroyed). We need to do nothing here or
  // else GetTabAt below will crash.
  if (tab_count() == 0)
    return;

  // It is critically important that this is unhooked here, otherwise we will
  // keep spying on messages forever.
  RemoveMessageLoopObserver();

  in_tab_close_ = false;
  available_width_for_tabs_ = -1;
  int mini_tab_count = GetMiniTabCount();
  if (mini_tab_count == tab_count()) {
    // Only mini-tabs, we know the tab widths won't have changed (all
    // mini-tabs have the same width), so there is nothing to do.
    return;
  }
  Tab* first_tab  = GetTabAtTabDataIndex(mini_tab_count);
  double unselected, selected;
  GetDesiredTabWidths(tab_count(), mini_tab_count, &unselected, &selected);
  // TODO: this is always selected, should it be 'selected : unselected'?
  int w = Round(first_tab->IsActive() ? selected : selected);

  // We only want to run the animation if we're not already at the desired
  // size.
  if (abs(first_tab->width() - w) > 1)
    StartResizeLayoutAnimation();
}

void TabStrip::AddMessageLoopObserver() {
  if (!mouse_watcher_.get()) {
    mouse_watcher_.reset(
        new views::MouseWatcher(this, this,
                                gfx::Insets(0, 0, kTabStripAnimationVSlop, 0)));
  }
  mouse_watcher_->Start();
}

void TabStrip::RemoveMessageLoopObserver() {
  mouse_watcher_.reset(NULL);
}

gfx::Rect TabStrip::GetDropBounds(int drop_index,
                                  bool drop_before,
                                  bool* is_beneath) {
  DCHECK(drop_index != -1);
  int center_x;
  if (drop_index < tab_count()) {
    Tab* tab = GetTabAtTabDataIndex(drop_index);
    if (drop_before)
      center_x = tab->x() - (kTabHOffset / 2);
    else
      center_x = tab->x() + (tab->width() / 2);
  } else {
    Tab* last_tab = GetTabAtTabDataIndex(drop_index - 1);
    center_x = last_tab->x() + last_tab->width() + (kTabHOffset / 2);
  }

  // Mirror the center point if necessary.
  center_x = GetMirroredXInView(center_x);

  // Determine the screen bounds.
  gfx::Point drop_loc(center_x - drop_indicator_width / 2,
                      -drop_indicator_height);
  ConvertPointToScreen(this, &drop_loc);
  gfx::Rect drop_bounds(drop_loc.x(), drop_loc.y(), drop_indicator_width,
                        drop_indicator_height);

  // If the rect doesn't fit on the monitor, push the arrow to the bottom.
#if defined(OS_WIN)
  gfx::Rect monitor_bounds = views::GetMonitorBoundsForRect(drop_bounds);
  *is_beneath = (monitor_bounds.IsEmpty() ||
                 !monitor_bounds.Contains(drop_bounds));
#else
  *is_beneath = false;
  NOTIMPLEMENTED();
#endif
  if (*is_beneath)
    drop_bounds.Offset(0, drop_bounds.height() + height());

  return drop_bounds;
}

void TabStrip::UpdateDropIndex(const DropTargetEvent& event) {
  // If the UI layout is right-to-left, we need to mirror the mouse
  // coordinates since we calculate the drop index based on the
  // original (and therefore non-mirrored) positions of the tabs.
  const int x = GetMirroredXInView(event.x());
  // We don't allow replacing the urls of mini-tabs.
  for (int i = GetMiniTabCount(); i < tab_count(); ++i) {
    Tab* tab = GetTabAtTabDataIndex(i);
    const int tab_max_x = tab->x() + tab->width();
    const int hot_width = tab->width() / 3;
    if (x < tab_max_x) {
      if (x < tab->x() + hot_width)
        SetDropIndex(i, true);
      else if (x >= tab_max_x - hot_width)
        SetDropIndex(i + 1, true);
      else
        SetDropIndex(i, false);
      return;
    }
  }

  // The drop isn't over a tab, add it to the end.
  SetDropIndex(tab_count(), true);
}

void TabStrip::SetDropIndex(int tab_data_index, bool drop_before) {
  if (tab_data_index == -1) {
    if (drop_info_.get())
      drop_info_.reset(NULL);
    return;
  }

  if (drop_info_.get() && drop_info_->drop_index == tab_data_index &&
      drop_info_->drop_before == drop_before) {
    return;
  }

  bool is_beneath;
  gfx::Rect drop_bounds = GetDropBounds(tab_data_index, drop_before,
                                        &is_beneath);

  if (!drop_info_.get()) {
    drop_info_.reset(new DropInfo(tab_data_index, drop_before, !is_beneath));
  } else {
    drop_info_->drop_index = tab_data_index;
    drop_info_->drop_before = drop_before;
    if (is_beneath == drop_info_->point_down) {
      drop_info_->point_down = !is_beneath;
      drop_info_->arrow_view->SetImage(
          GetDropArrowImage(drop_info_->point_down));
    }
  }

  // Reposition the window. Need to show it too as the window is initially
  // hidden.
  drop_info_->arrow_window->SetBounds(drop_bounds);
  drop_info_->arrow_window->Show();
}

int TabStrip::GetDropEffect(const views::DropTargetEvent& event) {
  const int source_ops = event.source_operations();
  if (source_ops & ui::DragDropTypes::DRAG_COPY)
    return ui::DragDropTypes::DRAG_COPY;
  if (source_ops & ui::DragDropTypes::DRAG_LINK)
    return ui::DragDropTypes::DRAG_LINK;
  return ui::DragDropTypes::DRAG_MOVE;
}

// static
SkBitmap* TabStrip::GetDropArrowImage(bool is_down) {
  return ResourceBundle::GetSharedInstance().GetBitmapNamed(
      is_down ? IDR_TAB_DROP_DOWN : IDR_TAB_DROP_UP);
}

// TabStrip::DropInfo ----------------------------------------------------------

TabStrip::DropInfo::DropInfo(int drop_index, bool drop_before, bool point_down)
    : drop_index(drop_index),
      drop_before(drop_before),
      point_down(point_down) {
  arrow_view = new views::ImageView;
  arrow_view->SetImage(GetDropArrowImage(point_down));

  views::Widget::CreateParams params(views::Widget::CreateParams::TYPE_POPUP);
  params.keep_on_top = true;
  params.transparent = true;
  params.accept_events = false;
  params.can_activate = false;
  arrow_window = views::Widget::CreateWidget(params);
  arrow_window->Init(
      NULL,
      gfx::Rect(0, 0, drop_indicator_width, drop_indicator_height));
  arrow_window->SetContentsView(arrow_view);
}

TabStrip::DropInfo::~DropInfo() {
  // Close eventually deletes the window, which deletes arrow_view too.
  arrow_window->Close();
}

///////////////////////////////////////////////////////////////////////////////

// Called from:
// - BasicLayout
// - Tab insertion/removal
// - Tab reorder
void TabStrip::GenerateIdealBounds() {
  int non_closing_tab_count = 0;
  int mini_tab_count = 0;
  for (int i = 0; i < tab_count(); ++i) {
    BaseTab* tab = base_tab_at_tab_index(i);
    if (!tab->closing()) {
      ++non_closing_tab_count;
      if (tab->data().mini)
        mini_tab_count++;
    }
  }

  double unselected, selected;
  GetDesiredTabWidths(non_closing_tab_count, mini_tab_count, &unselected,
                      &selected);

  current_unselected_width_ = unselected;
  current_selected_width_ = selected;

  // NOTE: This currently assumes a tab's height doesn't differ based on
  // selected state or the number of tabs in the strip!
  int tab_height = Tab::GetStandardSize().height();
  double tab_x = 0;
  bool last_was_mini = false;
  for (int i = 0; i < tab_count(); ++i) {
    Tab* tab = GetTabAtTabDataIndex(i);
    if (!tab->closing()) {
      double tab_width = unselected;
      if (tab->data().mini) {
        tab_width = Tab::GetMiniWidth();
      } else {
        if (last_was_mini) {
          // Give a bigger gap between mini and non-mini tabs.
          tab_x += mini_to_non_mini_gap_;
        }
        if (tab->IsActive())
          tab_width = selected;
      }
      double end_of_tab = tab_x + tab_width;
      int rounded_tab_x = Round(tab_x);
      set_ideal_bounds(i,
          gfx::Rect(rounded_tab_x, 0, Round(end_of_tab) - rounded_tab_x,
                    tab_height));
      tab_x = end_of_tab + kTabHOffset;
      last_was_mini = tab->data().mini;
    }
  }

  // Update bounds of new tab button.
  int new_tab_x;
  int new_tab_y = browser_defaults::kSizeTabButtonToTopOfTabStrip ?
      0 : kNewTabButtonVOffset;
  if (abs(Round(unselected) - Tab::GetStandardSize().width()) > 1 &&
      !in_tab_close_) {
    // We're shrinking tabs, so we need to anchor the New Tab button to the
    // right edge of the TabStrip's bounds, rather than the right edge of the
    // right-most Tab, otherwise it'll bounce when animating.
    new_tab_x = width() - newtab_button_bounds_.width();
  } else {
    new_tab_x = Round(tab_x - kTabHOffset) + kNewTabButtonHOffset;
  }
  newtab_button_bounds_.set_origin(gfx::Point(new_tab_x, new_tab_y));
}

void TabStrip::StartResizeLayoutAnimation() {
  PrepareForAnimation();
  GenerateIdealBounds();
  AnimateToIdealBounds();
}

void TabStrip::StartMiniTabAnimation() {
  in_tab_close_ = false;
  available_width_for_tabs_ = -1;

  PrepareForAnimation();

  GenerateIdealBounds();
  AnimateToIdealBounds();
}

void TabStrip::StartMouseInitiatedRemoveTabAnimation(int model_index) {
  // The user initiated the close. We want to persist the bounds of all the
  // existing tabs, so we manually shift ideal_bounds then animate.
  int tab_data_index = ModelIndexToTabIndex(model_index);
  DCHECK(tab_data_index != tab_count());
  BaseTab* tab_closing = base_tab_at_tab_index(tab_data_index);
  int delta = tab_closing->width() + kTabHOffset;
  if (tab_closing->data().mini && model_index + 1 < GetModelCount() &&
      !GetBaseTabAtModelIndex(model_index + 1)->data().mini) {
    delta += mini_to_non_mini_gap_;
  }

  for (int i = tab_data_index + 1; i < tab_count(); ++i) {
    BaseTab* tab = base_tab_at_tab_index(i);
    if (!tab->closing()) {
      gfx::Rect bounds = ideal_bounds(i);
      bounds.set_x(bounds.x() - delta);
      set_ideal_bounds(i, bounds);
    }
  }

  newtab_button_bounds_.set_x(newtab_button_bounds_.x() - delta);

  PrepareForAnimation();

  // Mark the tab as closing.
  tab_closing->set_closing(true);

  AnimateToIdealBounds();

  gfx::Rect tab_bounds = tab_closing->bounds();
  if (type() == HORIZONTAL_TAB_STRIP)
    tab_bounds.set_width(0);
  else
    tab_bounds.set_height(0);
  bounds_animator().AnimateViewTo(tab_closing, tab_bounds);

  // Register delegate to do cleanup when done, BoundsAnimator takes
  // ownership of RemoveTabDelegate.
  bounds_animator().SetAnimationDelegate(tab_closing,
                                         CreateRemoveTabDelegate(tab_closing),
                                         true);
}

int TabStrip::GetMiniTabCount() const {
  int mini_count = 0;
  for (int i = 0; i < tab_count(); ++i) {
    if (base_tab_at_tab_index(i)->data().mini)
      mini_count++;
    else
      return mini_count;
  }
  return mini_count;
}

int TabStrip::GetAvailableWidthForTabs(Tab* last_tab) const {
  return last_tab->x() + last_tab->width();
}

bool TabStrip::IsPointInTab(Tab* tab,
                            const gfx::Point& point_in_tabstrip_coords) {
  gfx::Point point_in_tab_coords(point_in_tabstrip_coords);
  View::ConvertPointToView(this, tab, &point_in_tab_coords);
  return tab->HitTest(point_in_tab_coords);
}