third_party/WebKit/Source/platform/scroll/ScrollAlignment.h

/*
 * Copyright (C) 2003, 2009 Apple Inc.  All rights reserved.
 *
 * Portions are Copyright (C) 1998 Netscape Communications Corporation.
 *
 * Other contributors:
 *   Robert O'Callahan <roc+@cs.cmu.edu>
 *   David Baron <dbaron@fas.harvard.edu>
 *   Christian Biesinger <cbiesinger@web.de>
 *   Randall Jesup <rjesup@wgate.com>
 *   Roland Mainz <roland.mainz@informatik.med.uni-giessen.de>
 *   Josh Soref <timeless@mac.com>
 *   Boris Zbarsky <bzbarsky@mit.edu>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
 *
 * Alternatively, the contents of this file may be used under the terms
 * of either the Mozilla Public License Version 1.1, found at
 * http://www.mozilla.org/MPL/ (the "MPL") or the GNU General Public
 * License Version 2.0, found at http://www.fsf.org/copyleft/gpl.html
 * (the "GPL"), in which case the provisions of the MPL or the GPL are
 * applicable instead of those above.  If you wish to allow use of your
 * version of this file only under the terms of one of those two
 * licenses (the MPL or the GPL) and not to allow others to use your
 * version of this file under the LGPL, indicate your decision by
 * deletingthe provisions above and replace them with the notice and
 * other provisions required by the MPL or the GPL, as the case may be.
 * If you do not delete the provisions above, a recipient may use your
 * version of this file under any of the LGPL, the MPL or the GPL.
 */

#ifndef ScrollAlignment_h
#define ScrollAlignment_h

#include "platform/PlatformExport.h"
#include "platform/scroll/ScrollTypes.h"
#include "platform/wtf/Allocator.h"

namespace blink {

enum ScrollAlignmentBehavior {
  kScrollAlignmentNoScroll,
  kScrollAlignmentCenter,
  kScrollAlignmentTop,
  kScrollAlignmentBottom,
  kScrollAlignmentLeft,
  kScrollAlignmentRight,
  kScrollAlignmentClosestEdge
};

class LayoutRect;

struct PLATFORM_EXPORT ScrollAlignment {
  STACK_ALLOCATED();
  static ScrollAlignmentBehavior GetVisibleBehavior(const ScrollAlignment& s) {
    return s.rect_visible_;
  }
  static ScrollAlignmentBehavior GetPartialBehavior(const ScrollAlignment& s) {
    return s.rect_partial_;
  }
  static ScrollAlignmentBehavior GetHiddenBehavior(const ScrollAlignment& s) {
    return s.rect_hidden_;
  }

  // Returns the scroll offset the scroller needs to scroll to in order to put
  // |expose_rect| into |visible_scroll_snapport_rect| aligned by |align_x| and
  // |align_y|.
  // The coordinates for |visible_scroll_snapport_rect|, |expose_rect| and
  // |current_scroll_position| are based on the scroller's scroll_origin
  // Note that the |current_scroll_offset| is not the location of
  // |visible_scroll_snapport_rect|, as |visible_scroll_snapport_rect| is the
  // visible rect contracted by its scroll-padding.
  // FIXME: This function should probably go somewhere else but where?
  static ScrollOffset GetScrollOffsetToExpose(
      const LayoutRect& visible_scroll_snapport_rect,
      const LayoutRect& expose_rect,
      const ScrollAlignment& align_x,
      const ScrollAlignment& align_y,
      const ScrollOffset& current_scroll_offset);

  static const ScrollAlignment kAlignCenterIfNeeded;
  static const ScrollAlignment kAlignToEdgeIfNeeded;
  static const ScrollAlignment kAlignCenterAlways;
  static const ScrollAlignment kAlignTopAlways;
  static const ScrollAlignment kAlignBottomAlways;
  static const ScrollAlignment kAlignLeftAlways;
  static const ScrollAlignment kAlignRightAlways;

  ScrollAlignmentBehavior rect_visible_;
  ScrollAlignmentBehavior rect_hidden_;
  ScrollAlignmentBehavior rect_partial_;
};

inline bool PLATFORM_EXPORT operator==(const ScrollAlignment& lhs,
                                       const ScrollAlignment& rhs) {
  return lhs.rect_visible_ == rhs.rect_visible_ &&
         lhs.rect_hidden_ == rhs.rect_hidden_ &&
         lhs.rect_partial_ == rhs.rect_partial_;
}

}  // namespace blink

#endif  // ScrollAlignment_h