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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+/**
+ * compute sticky positioning, both during reflow and when the scrolling
+ * container scrolls
+ */
+
+#ifndef StickyScrollContainer_h
+#define StickyScrollContainer_h
+
+#include "nsPoint.h"
+#include "nsRectAbsolute.h"
+#include "nsTArray.h"
+#include "nsIScrollPositionListener.h"
+
+struct nsRect;
+class nsIFrame;
+class nsIScrollableFrame;
+
+namespace mozilla {
+
+class StickyScrollContainer final : public nsIScrollPositionListener {
+ public:
+ /**
+ * Find (and create if necessary) the StickyScrollContainer associated with
+ * the scroll container of the given frame, if a scroll container exists.
+ */
+ static StickyScrollContainer* GetStickyScrollContainerForFrame(
+ nsIFrame* aFrame);
+
+ /**
+ * Find the StickyScrollContainer associated with the given scroll frame,
+ * if it exists.
+ */
+ static StickyScrollContainer* GetStickyScrollContainerForScrollFrame(
+ nsIFrame* aScrollFrame);
+
+ /**
+ * aFrame may have moved into or out of a scroll frame's frame subtree.
+ */
+ static void NotifyReparentedFrameAcrossScrollFrameBoundary(
+ nsIFrame* aFrame, nsIFrame* aOldParent);
+
+ void AddFrame(nsIFrame* aFrame) { mFrames.AppendElement(aFrame); }
+ void RemoveFrame(nsIFrame* aFrame) { mFrames.RemoveElement(aFrame); }
+
+ nsIScrollableFrame* ScrollFrame() const { return mScrollFrame; }
+
+ // Compute the offsets for a sticky position element
+ static void ComputeStickyOffsets(nsIFrame* aFrame);
+
+ /**
+ * Compute the position of a sticky positioned frame, based on information
+ * stored in its properties along with our scroll frame and scroll position.
+ */
+ nsPoint ComputePosition(nsIFrame* aFrame) const;
+
+ /**
+ * Compute where a frame should not scroll with the page, represented by the
+ * difference of two rectangles.
+ */
+ void GetScrollRanges(nsIFrame* aFrame, nsRectAbsolute* aOuter,
+ nsRectAbsolute* aInner) const;
+
+ /**
+ * Compute and set the position of a frame and its following continuations.
+ */
+ void PositionContinuations(nsIFrame* aFrame);
+
+ /**
+ * Compute and set the position of all sticky frames, given the current
+ * scroll position of the scroll frame. If not in reflow, aSubtreeRoot should
+ * be null; otherwise, overflow-area updates will be limited to not affect
+ * aSubtreeRoot or its ancestors.
+ */
+ void UpdatePositions(nsPoint aScrollPosition, nsIFrame* aSubtreeRoot);
+
+ // nsIScrollPositionListener
+ virtual void ScrollPositionWillChange(nscoord aX, nscoord aY) override;
+ virtual void ScrollPositionDidChange(nscoord aX, nscoord aY) override;
+
+ ~StickyScrollContainer();
+
+ const nsTArray<nsIFrame*>& GetFrames() const { return mFrames; }
+
+ /**
+ * Returns true if the frame is "stuck" in the y direction, ie it's acting
+ * like fixed position. aFrame should be in GetFrames().
+ */
+ bool IsStuckInYDirection(nsIFrame* aFrame) const;
+
+ private:
+ explicit StickyScrollContainer(nsIScrollableFrame* aScrollFrame);
+
+ /**
+ * Compute two rectangles that determine sticky positioning: |aStick|, based
+ * on the scroll container, and |aContain|, based on the containing block.
+ * Sticky positioning keeps the frame position (its upper-left corner) always
+ * within |aContain| and secondarily within |aStick|.
+ */
+ void ComputeStickyLimits(nsIFrame* aFrame, nsRect* aStick,
+ nsRect* aContain) const;
+
+ nsIScrollableFrame* const mScrollFrame;
+ nsTArray<nsIFrame*> mFrames;
+ nsPoint mScrollPosition;
+};
+
+} // namespace mozilla
+
+#endif /* StickyScrollContainer_h */