зеркало из https://github.com/mozilla/gecko-dev.git
79 строки
3.1 KiB
C++
79 строки
3.1 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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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 <memory>
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#include "mozilla/ScrollTypes.h"
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#include "mozilla/ScrollSnapTargetId.h"
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#include "mozilla/Maybe.h"
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class nsIContent;
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class nsIFrame;
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struct nsPoint;
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struct nsRect;
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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| and |aScrollRange| are characteristics of the scroll frame for
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* 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<SnapTarget> GetSnapPointForDestination(
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const layers::ScrollSnapInfo& aSnapInfo, ScrollUnit aUnit,
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ScrollSnapFlags aSnapFlags, const nsRect& aScrollRange,
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const nsPoint& aStartPos, const nsPoint& aDestination);
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/**
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* Similar to above GetSnapPointForDestination but for re-snapping.
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*
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* |aCurrentPosition| are the snap point(s) last time when we scrolled.
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* |aLastSnapTargetIds| are the snap point(s) last time when we scrolled if
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* exists.
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* |aFocusedContent| is the focused content in the document if exists.
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* Other parameters are same as GetSnapPointForDestination.
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*/
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static mozilla::Maybe<mozilla::SnapTarget> GetSnapPointForResnap(
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const layers::ScrollSnapInfo& aSnapInfo, const nsRect& aScrollRange,
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const nsPoint& aCurrentPosition,
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const UniquePtr<ScrollSnapTargetIds>& aLastSnapTargetIds,
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const nsIContent* aFocusedContent);
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static ScrollSnapTargetId GetTargetIdFor(const nsIFrame* aFrame);
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// Post a pending re-snap request if the given |aFrame| is one of the snap
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// points on the last scroll operation.
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static void PostPendingResnapIfNeededFor(nsIFrame* aFrame);
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// Similar to above PostPendingResnapIfNeededFor but post a pending re-snap
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// request even if the given |aFrame| is not one of the last snap point.
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// This is basically used for cases there was no valid snap point on the last
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// scroll operation but the given |aFrame| might be a valid snap point now,
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// e.g changing the scroll-snap-align property from `none` to something.
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static void PostPendingResnapFor(nsIFrame* aFrame);
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};
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} // namespace mozilla
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#endif // mozilla_layout_ScrollSnap_h_
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