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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef mozilla_layout_ScrollSnap_h_
#define mozilla_layout_ScrollSnap_h_
#include "nsIScrollableFrame.h"
namespace mozilla {
namespace layers {
struct ScrollSnapInfo;
}
struct ScrollSnapUtils {
/**
* GetSnapPointForDestination determines which point to snap to after
* scrolling. |aStartPos| gives the position before scrolling and
* |aDestination| gives the position after scrolling, with no snapping.
* Behaviour is dependent on the value of |aUnit|.
* |aSnapInfo|, |aScrollPortSize|, and |aScrollRange| are characteristics
* of the scroll frame for which snapping is being performed.
* If a suitable snap point could be found, it is returned. Otherwise, an
* empty Maybe is returned.
* IMPORTANT NOTE: This function is designed to be called both on and off
* the main thread. If modifying its implementation, be sure
* not to touch main-thread-only data structures without
* appropriate locking.
*/
static Maybe<nsPoint> GetSnapPointForDestination(
const layers::ScrollSnapInfo& aSnapInfo,
nsIScrollableFrame::ScrollUnit aUnit,
const nsSize& aScrollPortSize,
const nsRect& aScrollRange,
const nsPoint& aStartPos,
const nsPoint& aDestination);
};
} // namespace mozilla
#endif // mozilla_layout_ScrollSnap_h_
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