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