chromium/third_party/blink/renderer/core/paint/paint_layer_scrollable_area.h

/*
 * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
 *
 * Portions are Copyright (C) 1998 Netscape Communications Corporation.
 *
 * Other contributors:
 *   Robert O'Callahan <[email protected]>
 *   David Baron <[email protected]>
 *   Christian Biesinger <[email protected]>
 *   Randall Jesup <[email protected]>
 *   Roland Mainz <[email protected]>
 *   Josh Soref <[email protected]>
 *   Boris Zbarsky <[email protected]>
 *
 * 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 THIRD_PARTY_BLINK_RENDERER_CORE_PAINT_PAINT_LAYER_SCROLLABLE_AREA_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_PAINT_PAINT_LAYER_SCROLLABLE_AREA_H_

#include "base/check_op.h"
#include "base/task/single_thread_task_runner.h"
#include "cc/input/snap_selection_strategy.h"
#include "third_party/blink/public/mojom/scroll/scroll_into_view_params.mojom-blink-forward.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/layout/scroll_anchor.h"
#include "third_party/blink/renderer/core/scroll/scrollable_area.h"
#include "third_party/blink/renderer/platform/graphics/overlay_scrollbar_clip_behavior.h"
#include "third_party/blink/renderer/platform/heap/collection_support/heap_hash_set.h"
#include "third_party/blink/renderer/platform/heap/collection_support/heap_linked_hash_set.h"
#include "third_party/blink/renderer/platform/heap/collection_support/heap_vector.h"
#include "third_party/blink/renderer/platform/heap/garbage_collected.h"
#include "third_party/blink/renderer/platform/heap/persistent.h"

namespace blink {

enum ResizerHitTestType { … };

class ComputedStyle;
class Element;
class HitTestResult;
class LayoutBox;
class LayoutCustomScrollbarPart;
struct PaintInvalidatorContext;
class PaintLayer;
class ScrollingCoordinator;
class SnappedQueryScrollSnapshot;

struct CORE_EXPORT PaintLayerScrollableAreaRareData final
    : public GarbageCollected<PaintLayerScrollableAreaRareData> { … };

// PaintLayerScrollableArea represents the scrollable area of a LayoutBox.
//
// To be scrollable, an element requires ‘overflow’ != visible. Note that this
// doesn’t imply having scrollbars as you can always programmatically scroll
// when ‘overflow’ is hidden (using JavaScript's element.scrollTo or
// scrollLeft).
//
// The size and scroll origin of the scrollable area are based on layout
// dimensions. They are recomputed after layout in |UpdateScrollDimensions|.
//
// |UpdateScrollDimensions| also determines if scrollbars need to be allocated,
// destroyed or updated as a result of layout. This is based on the value of the
// 'overflow' property. Having non-overlay scrollbars automatically allocates a
// scrollcorner (|scroll_corner_|), which is used to style the intersection of
// the two scrollbars.
//
// Note that scrollbars are placed based on the LayoutBox's computed
// 'direction'. See https://webkit.org/b/54623 for some context.
//
// The ‘resize' property allocates a resizer (|resizer_|), which is overlaid on
// top of the scroll corner. It is used to resize an element using the mouse. A
// resizer can exist when there are no scrollbars.
//
// ***** OVERLAY OVERFLOW CONTROLS *****
// Overlay overflow controls are painted on top of the box's content, including
// overlay scrollbars and resizers (regardless of whether the scrollbars are
// overlaid). As such, they don't use any space in the box. Overlay overflow
// controls are painted by
// |PaintLayerPainter::PaintOverlayOverflowControlsForFragments| after all
// scrolling contents.
class CORE_EXPORT PaintLayerScrollableArea final
    : public GarbageCollected<PaintLayerScrollableArea>,
      public ScrollableArea { … };

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_PAINT_PAINT_LAYER_SCROLLABLE_AREA_H_