views/controls/scroll_view.cc - chromium/src - Git at Google

 // 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 "views/controls/scroll_view.h"

 #include "base/logging.h"
 #include "views/controls/scrollbar/native_scroll_bar.h"
 #include "views/widget/root_view.h"

 namespace views {

 const char* const ScrollView::kViewClassName = "views/ScrollView";

 // Viewport contains the contents View of the ScrollView.
 class Viewport : public View {
  public:
   Viewport() {}
   virtual ~Viewport() {}

   virtual std::string GetClassName() const {
     return "views/Viewport";
   }

   virtual void ScrollRectToVisible(const gfx::Rect& rect) {
     if (!has_children() || !parent())
       return;

     View* contents = child_at(0);
     gfx::Rect scroll_rect(rect);
     scroll_rect.Offset(-contents->x(), -contents->y());
     static_cast<ScrollView*>(parent())->ScrollContentsRegionToBeVisible(
         scroll_rect);
   }

  private:
   DISALLOW_COPY_AND_ASSIGN(Viewport);
 };


 ScrollView::ScrollView() {
   Init(new NativeScrollBar(true), new NativeScrollBar(false), NULL);
 }

 ScrollView::ScrollView(ScrollBar* horizontal_scrollbar,
                        ScrollBar* vertical_scrollbar,
                        View* resize_corner) {
   Init(horizontal_scrollbar, vertical_scrollbar, resize_corner);
 }

 ScrollView::~ScrollView() {
   // If scrollbars are currently not used, delete them
   if (!horiz_sb_->parent())
     delete horiz_sb_;

   if (!vert_sb_->parent())
     delete vert_sb_;

   if (resize_corner_ && !resize_corner_->parent())
     delete resize_corner_;
 }

 void ScrollView::SetContents(View* a_view) {
   if (contents_ && contents_ != a_view) {
     viewport_->RemoveChildView(contents_);
     delete contents_;
     contents_ = NULL;
   }

   if (a_view) {
     contents_ = a_view;
     viewport_->AddChildView(contents_);
   }

   Layout();
 }

 View* ScrollView::GetContents() const {
   return contents_;
 }

 void ScrollView::Init(ScrollBar* horizontal_scrollbar,
                       ScrollBar* vertical_scrollbar,
                       View* resize_corner) {
   DCHECK(horizontal_scrollbar && vertical_scrollbar);

   contents_ = NULL;
   horiz_sb_ = horizontal_scrollbar;
   vert_sb_ = vertical_scrollbar;
   resize_corner_ = resize_corner;

   viewport_ = new Viewport();
   AddChildView(viewport_);

   // Don't add the scrollbars as children until we discover we need them
   // (ShowOrHideScrollBar).
   horiz_sb_->SetVisible(false);
   horiz_sb_->set_controller(this);
   vert_sb_->SetVisible(false);
   vert_sb_->set_controller(this);
   if (resize_corner_)
     resize_corner_->SetVisible(false);
 }

 // Make sure that a single scrollbar is created and visible as needed
 void ScrollView::SetControlVisibility(View* control, bool should_show) {
   if (!control)
     return;
   if (should_show) {
     if (!control->IsVisible()) {
       AddChildView(control);
       control->SetVisible(true);
     }
   } else {
     RemoveChildView(control);
     control->SetVisible(false);
   }
 }

 void ScrollView::ComputeScrollBarsVisibility(const gfx::Size& vp_size,
                                              const gfx::Size& content_size,
                                              bool* horiz_is_shown,
                                              bool* vert_is_shown) const {
   // Try to fit both ways first, then try vertical bar only, then horizontal
   // bar only, then defaults to both shown.
   if (content_size.width() <= vp_size.width() &&
       content_size.height() <= vp_size.height()) {
     *horiz_is_shown = false;
     *vert_is_shown = false;
   } else if (content_size.width() <= vp_size.width() - GetScrollBarWidth()) {
     *horiz_is_shown = false;
     *vert_is_shown = true;
   } else if (content_size.height() <= vp_size.height() - GetScrollBarHeight()) {
     *horiz_is_shown = true;
     *vert_is_shown = false;
   } else {
     *horiz_is_shown = true;
     *vert_is_shown = true;
   }
 }

 void ScrollView::Layout() {
   // Most views will want to auto-fit the available space. Most of them want to
   // use the all available width (without overflowing) and only overflow in
   // height. Examples are HistoryView, MostVisitedView, DownloadTabView, etc.
   // Other views want to fit in both ways. An example is PrintView. To make both
   // happy, assume a vertical scrollbar but no horizontal scrollbar. To
   // override this default behavior, the inner view has to calculate the
   // available space, used ComputeScrollBarsVisibility() to use the same
   // calculation that is done here and sets its bound to fit within.
   gfx::Rect viewport_bounds = GetLocalBounds();
   // Realign it to 0 so it can be used as-is for SetBounds().
   viewport_bounds.set_origin(gfx::Point(0, 0));
   // viewport_size is the total client space available.
   gfx::Size viewport_size = viewport_bounds.size();
   if (viewport_bounds.IsEmpty()) {
     // There's nothing to layout.
     return;
   }

   // Assumes a vertical scrollbar since most the current views are designed for
   // this.
   int horiz_sb_height = GetScrollBarHeight();
   int vert_sb_width = GetScrollBarWidth();
   viewport_bounds.set_width(viewport_bounds.width() - vert_sb_width);
   // Update the bounds right now so the inner views can fit in it.
   viewport_->SetBoundsRect(viewport_bounds);

   // Give contents_ a chance to update its bounds if it depends on the
   // viewport.
   if (contents_)
     contents_->Layout();

   bool should_layout_contents = false;
   bool horiz_sb_required = false;
   bool vert_sb_required = false;
   if (contents_) {
     gfx::Size content_size = contents_->size();
     ComputeScrollBarsVisibility(viewport_size,
                                 content_size,
                                 &horiz_sb_required,
                                 &vert_sb_required);
   }
   bool resize_corner_required = resize_corner_ && horiz_sb_required &&
                                 vert_sb_required;
   // Take action.
   SetControlVisibility(horiz_sb_, horiz_sb_required);
   SetControlVisibility(vert_sb_, vert_sb_required);
   SetControlVisibility(resize_corner_, resize_corner_required);

   // Non-default.
   if (horiz_sb_required) {
     viewport_bounds.set_height(
         std::max(0, viewport_bounds.height() - horiz_sb_height));
     should_layout_contents = true;
   }
   // Default.
   if (!vert_sb_required) {
     viewport_bounds.set_width(viewport_bounds.width() + vert_sb_width);
     should_layout_contents = true;
   }

   if (horiz_sb_required) {
     horiz_sb_->SetBounds(0,
                          viewport_bounds.bottom(),
                          viewport_bounds.right(),
                          horiz_sb_height);
   }
   if (vert_sb_required) {
     vert_sb_->SetBounds(viewport_bounds.right(),
                         0,
                         vert_sb_width,
                         viewport_bounds.bottom());
   }
   if (resize_corner_required) {
     // Show the resize corner.
     resize_corner_->SetBounds(viewport_bounds.right(),
                               viewport_bounds.bottom(),
                               vert_sb_width,
                               horiz_sb_height);
   }

   // Update to the real client size with the visible scrollbars.
   viewport_->SetBoundsRect(viewport_bounds);
   if (should_layout_contents && contents_)
     contents_->Layout();

   CheckScrollBounds();
   SchedulePaint();
   UpdateScrollBarPositions();
 }

 int ScrollView::CheckScrollBounds(int viewport_size,
                                   int content_size,
                                   int current_pos) {
   int max = std::max(content_size - viewport_size, 0);
   if (current_pos < 0)
     current_pos = 0;
   else if (current_pos > max)
     current_pos = max;
   return current_pos;
 }

 void ScrollView::CheckScrollBounds() {
   if (contents_) {
     int x, y;

     x = CheckScrollBounds(viewport_->width(),
                           contents_->width(),
                           -contents_->x());
     y = CheckScrollBounds(viewport_->height(),
                           contents_->height(),
                           -contents_->y());

     // This is no op if bounds are the same
     contents_->SetBounds(-x, -y, contents_->width(), contents_->height());
   }
 }

 gfx::Rect ScrollView::GetVisibleRect() const {
   if (!contents_)
     return gfx::Rect();

   const int x =
       (horiz_sb_ && horiz_sb_->IsVisible()) ? horiz_sb_->GetPosition() : 0;
   const int y =
       (vert_sb_ && vert_sb_->IsVisible()) ? vert_sb_->GetPosition() : 0;
   return gfx::Rect(x, y, viewport_->width(), viewport_->height());
 }

 void ScrollView::ScrollContentsRegionToBeVisible(const gfx::Rect& rect) {
   if (!contents_ || ((!horiz_sb_ || !horiz_sb_->IsVisible()) &&
                      (!vert_sb_ || !vert_sb_->IsVisible()))) {
     return;
   }

   // Figure out the maximums for this scroll view.
   const int contents_max_x =
       std::max(viewport_->width(), contents_->width());
   const int contents_max_y =
       std::max(viewport_->height(), contents_->height());

   // Make sure x and y are within the bounds of [0,contents_max_*].
   int x = std::max(0, std::min(contents_max_x, rect.x()));
   int y = std::max(0, std::min(contents_max_y, rect.y()));

   // Figure out how far and down the rectangle will go taking width
   // and height into account.  This will be "clipped" by the viewport.
   const int max_x = std::min(contents_max_x,
                              x + std::min(rect.width(), viewport_->width()));
   const int max_y = std::min(contents_max_y,
                              y + std::min(rect.height(), viewport_->height()));

   // See if the rect is already visible. Note the width is (max_x - x)
   // and the height is (max_y - y) to take into account the clipping of
   // either viewport or the content size.
   const gfx::Rect vis_rect = GetVisibleRect();
   if (vis_rect.Contains(gfx::Rect(x, y, max_x - x, max_y - y)))
     return;

   // Shift contents_'s X and Y so that the region is visible. If we
   // need to shift up or left from where we currently are then we need
   // to get it so that the content appears in the upper/left
   // corner. This is done by setting the offset to -X or -Y.  For down
   // or right shifts we need to make sure it appears in the
   // lower/right corner. This is calculated by taking max_x or max_y
   // and scaling it back by the size of the viewport.
   const int new_x =
       (vis_rect.x() > x) ? x : std::max(0, max_x - viewport_->width());
   const int new_y =
       (vis_rect.y() > y) ? y : std::max(0, max_y - viewport_->height());

   contents_->SetX(-new_x);
   contents_->SetY(-new_y);
   UpdateScrollBarPositions();
 }

 void ScrollView::UpdateScrollBarPositions() {
   if (!contents_) {
     return;
   }

   if (horiz_sb_->IsVisible()) {
     int vw = viewport_->width();
     int cw = contents_->width();
     int origin = contents_->x();
     horiz_sb_->Update(vw, cw, -origin);
   }
   if (vert_sb_->IsVisible()) {
     int vh = viewport_->height();
     int ch = contents_->height();
     int origin = contents_->y();
     vert_sb_->Update(vh, ch, -origin);
   }
 }

 // TODO(ACW): We should really use ScrollWindowEx as needed
 void ScrollView::ScrollToPosition(ScrollBar* source, int position) {
   if (!contents_)
     return;

   if (source == horiz_sb_ && horiz_sb_->IsVisible()) {
     int vw = viewport_->width();
     int cw = contents_->width();
     int origin = contents_->x();
     if (-origin != position) {
       int max_pos = std::max(0, cw - vw);
       if (position < 0)
         position = 0;
       else if (position > max_pos)
         position = max_pos;
       contents_->SetX(-position);
       contents_->SchedulePaintInRect(contents_->GetVisibleBounds());
     }
   } else if (source == vert_sb_ && vert_sb_->IsVisible()) {
     int vh = viewport_->height();
     int ch = contents_->height();
     int origin = contents_->y();
     if (-origin != position) {
       int max_pos = std::max(0, ch - vh);
       if (position < 0)
         position = 0;
       else if (position > max_pos)
         position = max_pos;
       contents_->SetY(-position);
       contents_->SchedulePaintInRect(contents_->GetVisibleBounds());
     }
   }
 }

 int ScrollView::GetScrollIncrement(ScrollBar* source, bool is_page,
                                    bool is_positive) {
   bool is_horizontal = source->IsHorizontal();
   int amount = 0;
   View* view = GetContents();
   if (view) {
     if (is_page)
       amount = view->GetPageScrollIncrement(this, is_horizontal, is_positive);
     else
       amount = view->GetLineScrollIncrement(this, is_horizontal, is_positive);
     if (amount > 0)
       return amount;
   }
   // No view, or the view didn't return a valid amount.
   if (is_page)
     return is_horizontal ? viewport_->width() : viewport_->height();
   return is_horizontal ? viewport_->width() / 5 : viewport_->height() / 5;
 }

 bool ScrollView::OnKeyPressed(const KeyEvent& event) {
   bool processed = false;

   // Give vertical scrollbar priority
   if (vert_sb_->IsVisible()) {
     processed = vert_sb_->OnKeyPressed(event);
   }

   if (!processed && horiz_sb_->IsVisible()) {
     processed = horiz_sb_->OnKeyPressed(event);
   }
   return processed;
 }

 bool ScrollView::OnMouseWheel(const MouseWheelEvent& e) {
   bool processed = false;
   // Give vertical scrollbar priority
   if (vert_sb_->IsVisible()) {
     processed = vert_sb_->OnMouseWheel(e);
   }
   if (!processed && horiz_sb_->IsVisible()) {
     processed = horiz_sb_->OnMouseWheel(e);
   }
   return processed;
 }

 std::string ScrollView::GetClassName() const {
   return kViewClassName;
 }

 int ScrollView::GetScrollBarWidth() const {
   return vert_sb_->GetLayoutSize();
 }

 int ScrollView::GetScrollBarHeight() const {
   return horiz_sb_->GetLayoutSize();
 }

 // VariableRowHeightScrollHelper ----------------------------------------------

 VariableRowHeightScrollHelper::VariableRowHeightScrollHelper(
     Controller* controller) : controller_(controller) {
 }

 VariableRowHeightScrollHelper::~VariableRowHeightScrollHelper() {
 }

 int VariableRowHeightScrollHelper::GetPageScrollIncrement(
     ScrollView* scroll_view, bool is_horizontal, bool is_positive) {
   if (is_horizontal)
     return 0;
   // y coordinate is most likely negative.
   int y = abs(scroll_view->GetContents()->y());
   int vis_height = scroll_view->GetContents()->parent()->height();
   if (is_positive) {
     // Align the bottom most row to the top of the view.
     int bottom = std::min(scroll_view->GetContents()->height() - 1,
                           y + vis_height);
     RowInfo bottom_row_info = GetRowInfo(bottom);
     // If 0, ScrollView will provide a default value.
     return std::max(0, bottom_row_info.origin - y);
   } else {
     // Align the row on the previous page to to the top of the view.
     int last_page_y = y - vis_height;
     RowInfo last_page_info = GetRowInfo(std::max(0, last_page_y));
     if (last_page_y != last_page_info.origin)
       return std::max(0, y - last_page_info.origin - last_page_info.height);
     return std::max(0, y - last_page_info.origin);
   }
 }

 int VariableRowHeightScrollHelper::GetLineScrollIncrement(
     ScrollView* scroll_view, bool is_horizontal, bool is_positive) {
   if (is_horizontal)
     return 0;
   // y coordinate is most likely negative.
   int y = abs(scroll_view->GetContents()->y());
   RowInfo row = GetRowInfo(y);
   if (is_positive) {
     return row.height - (y - row.origin);
   } else if (y == row.origin) {
     row = GetRowInfo(std::max(0, row.origin - 1));
     return y - row.origin;
   } else {
     return y - row.origin;
   }
 }

 VariableRowHeightScrollHelper::RowInfo
     VariableRowHeightScrollHelper::GetRowInfo(int y) {
   return controller_->GetRowInfo(y);
 }

 // FixedRowHeightScrollHelper -----------------------------------------------

 FixedRowHeightScrollHelper::FixedRowHeightScrollHelper(int top_margin,
                                                        int row_height)
     : VariableRowHeightScrollHelper(NULL),
       top_margin_(top_margin),
       row_height_(row_height) {
   DCHECK_GT(row_height, 0);
 }

 VariableRowHeightScrollHelper::RowInfo
     FixedRowHeightScrollHelper::GetRowInfo(int y) {
   if (y < top_margin_)
     return RowInfo(0, top_margin_);
   return RowInfo((y - top_margin_) / row_height_ * row_height_ + top_margin_,
                  row_height_);
 }

 }  // namespace views
	// 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 "views/controls/scroll_view.h"

	#include "base/logging.h"
	#include "views/controls/scrollbar/native_scroll_bar.h"
	#include "views/widget/root_view.h"

	namespace views {

	const char* const ScrollView::kViewClassName = "views/ScrollView";

	// Viewport contains the contents View of the ScrollView.
	class Viewport : public View {
	public:
	Viewport() {}
	virtual ~Viewport() {}

	virtual std::string GetClassName() const {
	return "views/Viewport";
	}

	virtual void ScrollRectToVisible(const gfx::Rect& rect) {
	if (!has_children() \|\| !parent())
	return;

	View* contents = child_at(0);
	gfx::Rect scroll_rect(rect);
	scroll_rect.Offset(-contents->x(), -contents->y());
	static_cast<ScrollView*>(parent())->ScrollContentsRegionToBeVisible(
	scroll_rect);
	}

	private:
	DISALLOW_COPY_AND_ASSIGN(Viewport);
	};


	ScrollView::ScrollView() {
	Init(new NativeScrollBar(true), new NativeScrollBar(false), NULL);
	}

	ScrollView::ScrollView(ScrollBar* horizontal_scrollbar,
	ScrollBar* vertical_scrollbar,
	View* resize_corner) {
	Init(horizontal_scrollbar, vertical_scrollbar, resize_corner);
	}

	ScrollView::~ScrollView() {
	// If scrollbars are currently not used, delete them
	if (!horiz_sb_->parent())
	delete horiz_sb_;

	if (!vert_sb_->parent())
	delete vert_sb_;

	if (resize_corner_ && !resize_corner_->parent())
	delete resize_corner_;
	}

	void ScrollView::SetContents(View* a_view) {
	if (contents_ && contents_ != a_view) {
	viewport_->RemoveChildView(contents_);
	delete contents_;
	contents_ = NULL;
	}

	if (a_view) {
	contents_ = a_view;
	viewport_->AddChildView(contents_);
	}

	Layout();
	}

	View* ScrollView::GetContents() const {
	return contents_;
	}

	void ScrollView::Init(ScrollBar* horizontal_scrollbar,
	ScrollBar* vertical_scrollbar,
	View* resize_corner) {
	DCHECK(horizontal_scrollbar && vertical_scrollbar);

	contents_ = NULL;
	horiz_sb_ = horizontal_scrollbar;
	vert_sb_ = vertical_scrollbar;
	resize_corner_ = resize_corner;

	viewport_ = new Viewport();
	AddChildView(viewport_);

	// Don't add the scrollbars as children until we discover we need them
	// (ShowOrHideScrollBar).
	horiz_sb_->SetVisible(false);
	horiz_sb_->set_controller(this);
	vert_sb_->SetVisible(false);
	vert_sb_->set_controller(this);
	if (resize_corner_)
	resize_corner_->SetVisible(false);
	}

	// Make sure that a single scrollbar is created and visible as needed
	void ScrollView::SetControlVisibility(View* control, bool should_show) {
	if (!control)
	return;
	if (should_show) {
	if (!control->IsVisible()) {
	AddChildView(control);
	control->SetVisible(true);
	}
	} else {
	RemoveChildView(control);
	control->SetVisible(false);
	}
	}

	void ScrollView::ComputeScrollBarsVisibility(const gfx::Size& vp_size,
	const gfx::Size& content_size,
	bool* horiz_is_shown,
	bool* vert_is_shown) const {
	// Try to fit both ways first, then try vertical bar only, then horizontal
	// bar only, then defaults to both shown.
	if (content_size.width() <= vp_size.width() &&
	content_size.height() <= vp_size.height()) {
	*horiz_is_shown = false;
	*vert_is_shown = false;
	} else if (content_size.width() <= vp_size.width() - GetScrollBarWidth()) {
	*horiz_is_shown = false;
	*vert_is_shown = true;
	} else if (content_size.height() <= vp_size.height() - GetScrollBarHeight()) {
	*horiz_is_shown = true;
	*vert_is_shown = false;
	} else {
	*horiz_is_shown = true;
	*vert_is_shown = true;
	}
	}

	void ScrollView::Layout() {
	// Most views will want to auto-fit the available space. Most of them want to
	// use the all available width (without overflowing) and only overflow in
	// height. Examples are HistoryView, MostVisitedView, DownloadTabView, etc.
	// Other views want to fit in both ways. An example is PrintView. To make both
	// happy, assume a vertical scrollbar but no horizontal scrollbar. To
	// override this default behavior, the inner view has to calculate the
	// available space, used ComputeScrollBarsVisibility() to use the same
	// calculation that is done here and sets its bound to fit within.
	gfx::Rect viewport_bounds = GetLocalBounds();
	// Realign it to 0 so it can be used as-is for SetBounds().
	viewport_bounds.set_origin(gfx::Point(0, 0));
	// viewport_size is the total client space available.
	gfx::Size viewport_size = viewport_bounds.size();
	if (viewport_bounds.IsEmpty()) {
	// There's nothing to layout.
	return;
	}

	// Assumes a vertical scrollbar since most the current views are designed for
	// this.
	int horiz_sb_height = GetScrollBarHeight();
	int vert_sb_width = GetScrollBarWidth();
	viewport_bounds.set_width(viewport_bounds.width() - vert_sb_width);
	// Update the bounds right now so the inner views can fit in it.
	viewport_->SetBoundsRect(viewport_bounds);

	// Give contents_ a chance to update its bounds if it depends on the
	// viewport.
	if (contents_)
	contents_->Layout();

	bool should_layout_contents = false;
	bool horiz_sb_required = false;
	bool vert_sb_required = false;
	if (contents_) {
	gfx::Size content_size = contents_->size();
	ComputeScrollBarsVisibility(viewport_size,
	content_size,
	&horiz_sb_required,
	&vert_sb_required);
	}
	bool resize_corner_required = resize_corner_ && horiz_sb_required &&
	vert_sb_required;
	// Take action.
	SetControlVisibility(horiz_sb_, horiz_sb_required);
	SetControlVisibility(vert_sb_, vert_sb_required);
	SetControlVisibility(resize_corner_, resize_corner_required);

	// Non-default.
	if (horiz_sb_required) {
	viewport_bounds.set_height(
	std::max(0, viewport_bounds.height() - horiz_sb_height));
	should_layout_contents = true;
	}
	// Default.
	if (!vert_sb_required) {
	viewport_bounds.set_width(viewport_bounds.width() + vert_sb_width);
	should_layout_contents = true;
	}

	if (horiz_sb_required) {
	horiz_sb_->SetBounds(0,
	viewport_bounds.bottom(),
	viewport_bounds.right(),
	horiz_sb_height);
	}
	if (vert_sb_required) {
	vert_sb_->SetBounds(viewport_bounds.right(),
	0,
	vert_sb_width,
	viewport_bounds.bottom());
	}
	if (resize_corner_required) {
	// Show the resize corner.
	resize_corner_->SetBounds(viewport_bounds.right(),
	viewport_bounds.bottom(),
	vert_sb_width,
	horiz_sb_height);
	}

	// Update to the real client size with the visible scrollbars.
	viewport_->SetBoundsRect(viewport_bounds);
	if (should_layout_contents && contents_)
	contents_->Layout();

	CheckScrollBounds();
	SchedulePaint();
	UpdateScrollBarPositions();
	}

	int ScrollView::CheckScrollBounds(int viewport_size,
	int content_size,
	int current_pos) {
	int max = std::max(content_size - viewport_size, 0);
	if (current_pos < 0)
	current_pos = 0;
	else if (current_pos > max)
	current_pos = max;
	return current_pos;
	}

	void ScrollView::CheckScrollBounds() {
	if (contents_) {
	int x, y;

	x = CheckScrollBounds(viewport_->width(),
	contents_->width(),
	-contents_->x());
	y = CheckScrollBounds(viewport_->height(),
	contents_->height(),
	-contents_->y());

	// This is no op if bounds are the same
	contents_->SetBounds(-x, -y, contents_->width(), contents_->height());
	}
	}

	gfx::Rect ScrollView::GetVisibleRect() const {
	if (!contents_)
	return gfx::Rect();

	const int x =
	(horiz_sb_ && horiz_sb_->IsVisible()) ? horiz_sb_->GetPosition() : 0;
	const int y =
	(vert_sb_ && vert_sb_->IsVisible()) ? vert_sb_->GetPosition() : 0;
	return gfx::Rect(x, y, viewport_->width(), viewport_->height());
	}

	void ScrollView::ScrollContentsRegionToBeVisible(const gfx::Rect& rect) {
	if (!contents_ \|\| ((!horiz_sb_ \|\| !horiz_sb_->IsVisible()) &&
	(!vert_sb_ \|\| !vert_sb_->IsVisible()))) {
	return;
	}

	// Figure out the maximums for this scroll view.
	const int contents_max_x =
	std::max(viewport_->width(), contents_->width());
	const int contents_max_y =
	std::max(viewport_->height(), contents_->height());

	// Make sure x and y are within the bounds of [0,contents_max_*].
	int x = std::max(0, std::min(contents_max_x, rect.x()));
	int y = std::max(0, std::min(contents_max_y, rect.y()));

	// Figure out how far and down the rectangle will go taking width
	// and height into account. This will be "clipped" by the viewport.
	const int max_x = std::min(contents_max_x,
	x + std::min(rect.width(), viewport_->width()));
	const int max_y = std::min(contents_max_y,
	y + std::min(rect.height(), viewport_->height()));

	// See if the rect is already visible. Note the width is (max_x - x)
	// and the height is (max_y - y) to take into account the clipping of
	// either viewport or the content size.
	const gfx::Rect vis_rect = GetVisibleRect();
	if (vis_rect.Contains(gfx::Rect(x, y, max_x - x, max_y - y)))
	return;

	// Shift contents_'s X and Y so that the region is visible. If we
	// need to shift up or left from where we currently are then we need
	// to get it so that the content appears in the upper/left
	// corner. This is done by setting the offset to -X or -Y. For down
	// or right shifts we need to make sure it appears in the
	// lower/right corner. This is calculated by taking max_x or max_y
	// and scaling it back by the size of the viewport.
	const int new_x =
	(vis_rect.x() > x) ? x : std::max(0, max_x - viewport_->width());
	const int new_y =
	(vis_rect.y() > y) ? y : std::max(0, max_y - viewport_->height());

	contents_->SetX(-new_x);
	contents_->SetY(-new_y);
	UpdateScrollBarPositions();
	}

	void ScrollView::UpdateScrollBarPositions() {
	if (!contents_) {
	return;
	}

	if (horiz_sb_->IsVisible()) {
	int vw = viewport_->width();
	int cw = contents_->width();
	int origin = contents_->x();
	horiz_sb_->Update(vw, cw, -origin);
	}
	if (vert_sb_->IsVisible()) {
	int vh = viewport_->height();
	int ch = contents_->height();
	int origin = contents_->y();
	vert_sb_->Update(vh, ch, -origin);
	}
	}

	// TODO(ACW): We should really use ScrollWindowEx as needed
	void ScrollView::ScrollToPosition(ScrollBar* source, int position) {
	if (!contents_)
	return;

	if (source == horiz_sb_ && horiz_sb_->IsVisible()) {
	int vw = viewport_->width();
	int cw = contents_->width();
	int origin = contents_->x();
	if (-origin != position) {
	int max_pos = std::max(0, cw - vw);
	if (position < 0)
	position = 0;
	else if (position > max_pos)
	position = max_pos;
	contents_->SetX(-position);
	contents_->SchedulePaintInRect(contents_->GetVisibleBounds());
	}
	} else if (source == vert_sb_ && vert_sb_->IsVisible()) {
	int vh = viewport_->height();
	int ch = contents_->height();
	int origin = contents_->y();
	if (-origin != position) {
	int max_pos = std::max(0, ch - vh);
	if (position < 0)
	position = 0;
	else if (position > max_pos)
	position = max_pos;
	contents_->SetY(-position);
	contents_->SchedulePaintInRect(contents_->GetVisibleBounds());
	}
	}
	}

	int ScrollView::GetScrollIncrement(ScrollBar* source, bool is_page,
	bool is_positive) {
	bool is_horizontal = source->IsHorizontal();
	int amount = 0;
	View* view = GetContents();
	if (view) {
	if (is_page)
	amount = view->GetPageScrollIncrement(this, is_horizontal, is_positive);
	else
	amount = view->GetLineScrollIncrement(this, is_horizontal, is_positive);
	if (amount > 0)
	return amount;
	}
	// No view, or the view didn't return a valid amount.
	if (is_page)
	return is_horizontal ? viewport_->width() : viewport_->height();
	return is_horizontal ? viewport_->width() / 5 : viewport_->height() / 5;
	}

	bool ScrollView::OnKeyPressed(const KeyEvent& event) {
	bool processed = false;

	// Give vertical scrollbar priority
	if (vert_sb_->IsVisible()) {
	processed = vert_sb_->OnKeyPressed(event);
	}

	if (!processed && horiz_sb_->IsVisible()) {
	processed = horiz_sb_->OnKeyPressed(event);
	}
	return processed;
	}

	bool ScrollView::OnMouseWheel(const MouseWheelEvent& e) {
	bool processed = false;
	// Give vertical scrollbar priority
	if (vert_sb_->IsVisible()) {
	processed = vert_sb_->OnMouseWheel(e);
	}
	if (!processed && horiz_sb_->IsVisible()) {
	processed = horiz_sb_->OnMouseWheel(e);
	}
	return processed;
	}

	std::string ScrollView::GetClassName() const {
	return kViewClassName;
	}

	int ScrollView::GetScrollBarWidth() const {
	return vert_sb_->GetLayoutSize();
	}

	int ScrollView::GetScrollBarHeight() const {
	return horiz_sb_->GetLayoutSize();
	}

	// VariableRowHeightScrollHelper ----------------------------------------------

	VariableRowHeightScrollHelper::VariableRowHeightScrollHelper(
	Controller* controller) : controller_(controller) {
	}

	VariableRowHeightScrollHelper::~VariableRowHeightScrollHelper() {
	}

	int VariableRowHeightScrollHelper::GetPageScrollIncrement(
	ScrollView* scroll_view, bool is_horizontal, bool is_positive) {
	if (is_horizontal)
	return 0;
	// y coordinate is most likely negative.
	int y = abs(scroll_view->GetContents()->y());
	int vis_height = scroll_view->GetContents()->parent()->height();
	if (is_positive) {
	// Align the bottom most row to the top of the view.
	int bottom = std::min(scroll_view->GetContents()->height() - 1,
	y + vis_height);
	RowInfo bottom_row_info = GetRowInfo(bottom);
	// If 0, ScrollView will provide a default value.
	return std::max(0, bottom_row_info.origin - y);
	} else {
	// Align the row on the previous page to to the top of the view.
	int last_page_y = y - vis_height;
	RowInfo last_page_info = GetRowInfo(std::max(0, last_page_y));
	if (last_page_y != last_page_info.origin)
	return std::max(0, y - last_page_info.origin - last_page_info.height);
	return std::max(0, y - last_page_info.origin);
	}
	}

	int VariableRowHeightScrollHelper::GetLineScrollIncrement(
	ScrollView* scroll_view, bool is_horizontal, bool is_positive) {
	if (is_horizontal)
	return 0;
	// y coordinate is most likely negative.
	int y = abs(scroll_view->GetContents()->y());
	RowInfo row = GetRowInfo(y);
	if (is_positive) {
	return row.height - (y - row.origin);
	} else if (y == row.origin) {
	row = GetRowInfo(std::max(0, row.origin - 1));
	return y - row.origin;
	} else {
	return y - row.origin;
	}
	}

	VariableRowHeightScrollHelper::RowInfo
	VariableRowHeightScrollHelper::GetRowInfo(int y) {
	return controller_->GetRowInfo(y);
	}

	// FixedRowHeightScrollHelper -----------------------------------------------

	FixedRowHeightScrollHelper::FixedRowHeightScrollHelper(int top_margin,
	int row_height)
	: VariableRowHeightScrollHelper(NULL),
	top_margin_(top_margin),
	row_height_(row_height) {
	DCHECK_GT(row_height, 0);
	}

	VariableRowHeightScrollHelper::RowInfo
	FixedRowHeightScrollHelper::GetRowInfo(int y) {
	if (y < top_margin_)
	return RowInfo(0, top_margin_);
	return RowInfo((y - top_margin_) / row_height_ * row_height_ + top_margin_,
	row_height_);
	}

	} // namespace views