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285 lines
11 KiB
C++
285 lines
11 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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/*
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* interface that provides scroll APIs implemented by scrollable frames
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*/
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#ifndef nsIScrollFrame_h___
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#define nsIScrollFrame_h___
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#include "nsCoord.h"
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#include "ScrollbarStyles.h"
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#include "mozilla/gfx/Point.h"
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#include "nsIScrollbarOwner.h"
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#include "Units.h"
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#define NS_DEFAULT_VERTICAL_SCROLL_DISTANCE 3
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#define NS_DEFAULT_HORIZONTAL_SCROLL_DISTANCE 5
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class nsBoxLayoutState;
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class nsIScrollPositionListener;
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class nsIFrame;
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class nsPresContext;
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class nsIContent;
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class nsRenderingContext;
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class nsIAtom;
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/**
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* Interface for frames that are scrollable. This interface exposes
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* APIs for examining scroll state, observing changes to scroll state,
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* and triggering scrolling.
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*/
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class nsIScrollableFrame : public nsIScrollbarOwner {
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public:
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typedef mozilla::CSSIntPoint CSSIntPoint;
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NS_DECL_QUERYFRAME_TARGET(nsIScrollableFrame)
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/**
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* Get the frame for the content that we are scrolling within
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* this scrollable frame.
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*/
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virtual nsIFrame* GetScrolledFrame() const = 0;
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/**
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* Get the styles (NS_STYLE_OVERFLOW_SCROLL, NS_STYLE_OVERFLOW_HIDDEN,
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* or NS_STYLE_OVERFLOW_AUTO) governing the horizontal and vertical
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* scrollbars for this frame.
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*/
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virtual mozilla::ScrollbarStyles GetScrollbarStyles() const = 0;
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enum { HORIZONTAL = 0x01, VERTICAL = 0x02 };
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/**
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* Return the scrollbars which are visible. It's OK to call this during reflow
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* of the scrolled contents, in which case it will reflect the current
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* assumptions about scrollbar visibility.
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*/
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virtual uint32_t GetScrollbarVisibility() const = 0;
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/**
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* Returns the directions in which scrolling is perceived to be allowed.
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* A direction is perceived to be allowed if there is a visible scrollbar
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* for that direction or if the scroll range is at least one device pixel.
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*/
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uint32_t GetPerceivedScrollingDirections() const;
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/**
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* Return the actual sizes of all possible scrollbars. Returns 0 for scrollbar
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* positions that don't have a scrollbar or where the scrollbar is not visible.
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* Do not call this while this frame's descendants are being reflowed, it won't be
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* accurate.
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*/
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virtual nsMargin GetActualScrollbarSizes() const = 0;
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/**
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* Return the sizes of all scrollbars assuming that any scrollbars that could
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* be visible due to overflowing content, are. This can be called during reflow
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* of the scrolled contents.
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*/
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virtual nsMargin GetDesiredScrollbarSizes(nsBoxLayoutState* aState) = 0;
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/**
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* Return the sizes of all scrollbars assuming that any scrollbars that could
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* be visible due to overflowing content, are. This can be called during reflow
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* of the scrolled contents.
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*/
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virtual nsMargin GetDesiredScrollbarSizes(nsPresContext* aPresContext,
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nsRenderingContext* aRC) = 0;
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/**
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* Return the width for non-disappearing scrollbars.
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*/
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virtual nscoord GetNondisappearingScrollbarWidth(nsPresContext* aPresContext,
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nsRenderingContext* aRC) = 0;
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/**
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* GetScrolledRect is designed to encapsulate deciding which
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* directions of overflow should be reachable by scrolling and which
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* should not. Callers should NOT depend on it having any particular
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* behavior (although nsXULScrollFrame currently does).
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*
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* This should only be called when the scrolled frame has been
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* reflowed with the scroll port size given in mScrollPort.
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*
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* Currently it allows scrolling down and to the right for
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* nsHTMLScrollFrames with LTR directionality and for all
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* nsXULScrollFrames, and allows scrolling down and to the left for
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* nsHTMLScrollFrames with RTL directionality.
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*/
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virtual nsRect GetScrolledRect() const = 0;
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/**
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* Get the area of the scrollport relative to the origin of this frame's
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* border-box.
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* This is the area of this frame minus border and scrollbars.
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*/
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virtual nsRect GetScrollPortRect() const = 0;
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/**
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* Get the offset of the scrollport origin relative to the scrolled
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* frame origin. Typically the position will be non-negative.
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* This will always be a multiple of device pixels.
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*/
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virtual nsPoint GetScrollPosition() const = 0;
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/**
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* As GetScrollPosition(), but uses the top-right as origin for RTL frames.
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*/
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virtual nsPoint GetLogicalScrollPosition() const = 0;
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/**
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* Get the area that must contain the scroll position. Typically
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* (but not always, e.g. for RTL content) x and y will be 0, and
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* width or height will be nonzero if the content can be scrolled in
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* that direction. Since scroll positions must be a multiple of
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* device pixels, the range extrema will also be a multiple of
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* device pixels.
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*/
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virtual nsRect GetScrollRange() const = 0;
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/**
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* Get the size of the scroll port to use when clamping the scroll
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* position.
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*/
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virtual nsSize GetScrollPositionClampingScrollPortSize() const = 0;
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/**
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* Return how much we would try to scroll by in each direction if
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* asked to scroll by one "line" vertically and horizontally.
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*/
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virtual nsSize GetLineScrollAmount() const = 0;
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/**
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* Return how much we would try to scroll by in each direction if
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* asked to scroll by one "page" vertically and horizontally.
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*/
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virtual nsSize GetPageScrollAmount() const = 0;
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/**
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* When a scroll operation is requested, we ask for instant, smooth or normal
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* scrolling. SMOOTH will only be smooth if smooth scrolling is actually
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* enabled. INSTANT is always synchronous, NORMAL can be asynchronous.
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* If an INSTANT request happens while a smooth or async scroll is already in
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* progress, the async scroll is interrupted and we instantly scroll to the
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* destination.
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*/
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enum ScrollMode { INSTANT, SMOOTH, NORMAL };
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/**
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* @note This method might destroy the frame, pres shell and other objects.
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* Clamps aScrollPosition to GetScrollRange and sets the scroll position
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* to that value.
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* @param aRange If non-null, specifies area which contains aScrollPosition
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* and can be used for choosing a performance-optimized scroll position.
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* Any point within this area can be chosen.
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* The choosen point will be as close as possible to aScrollPosition.
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*/
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virtual void ScrollTo(nsPoint aScrollPosition, ScrollMode aMode,
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const nsRect* aRange = nullptr) = 0;
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/**
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* @note This method might destroy the frame, pres shell and other objects.
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* Scrolls to a particular position in integer CSS pixels.
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* Keeps the exact current horizontal or vertical position if the current
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* position, rounded to CSS pixels, matches aScrollPosition. If
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* aScrollPosition.x/y is different from the current CSS pixel position,
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* makes sure we only move in the direction given by the difference.
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* Ensures that GetScrollPositionCSSPixels (the scroll position after
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* rounding to CSS pixels) will be exactly aScrollPosition.
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* The scroll mode is INSTANT.
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*/
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virtual void ScrollToCSSPixels(const CSSIntPoint& aScrollPosition) = 0;
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/**
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* @note This method might destroy the frame, pres shell and other objects.
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* Scrolls to a particular position in float CSS pixels.
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* This does not guarantee that GetScrollPositionCSSPixels equals
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* aScrollPosition afterward. It tries to scroll as close to
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* aScrollPosition as possible while scrolling by an integer
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* number of layer pixels (so the operation is fast and looks clean).
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* The scroll mode is INSTANT.
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*/
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virtual void ScrollToCSSPixelsApproximate(const mozilla::CSSPoint& aScrollPosition,
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nsIAtom *aOrigin = nullptr) = 0;
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/**
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* Returns the scroll position in integer CSS pixels, rounded to the nearest
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* pixel.
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*/
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virtual CSSIntPoint GetScrollPositionCSSPixels() = 0;
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/**
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* When scrolling by a relative amount, we can choose various units.
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*/
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enum ScrollUnit { DEVICE_PIXELS, LINES, PAGES, WHOLE };
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/**
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* @note This method might destroy the frame, pres shell and other objects.
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* Modifies the current scroll position by aDelta units given by aUnit,
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* clamping it to GetScrollRange. If WHOLE is specified as the unit,
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* content is scrolled all the way in the direction(s) given by aDelta.
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* @param aOverflow if non-null, returns the amount that scrolling
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* was clamped by in each direction (how far we moved the scroll position
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* to bring it back into the legal range). This is never negative. The
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* values are in device pixels.
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*/
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virtual void ScrollBy(nsIntPoint aDelta, ScrollUnit aUnit, ScrollMode aMode,
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nsIntPoint* aOverflow = nullptr, nsIAtom *aOrigin = nullptr) = 0;
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/**
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* @note This method might destroy the frame, pres shell and other objects.
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* This tells the scroll frame to try scrolling to the scroll
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* position that was restored from the history. This must be called
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* at least once after state has been restored. It is called by the
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* scrolled frame itself during reflow, but sometimes state can be
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* restored after reflows are done...
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* XXX should we take an aMode parameter here? Currently it's instant.
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*/
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virtual void ScrollToRestoredPosition() = 0;
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/**
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* Add a scroll position listener. This listener must be removed
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* before it is destroyed.
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*/
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virtual void AddScrollPositionListener(nsIScrollPositionListener* aListener) = 0;
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/**
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* Remove a scroll position listener.
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*/
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virtual void RemoveScrollPositionListener(nsIScrollPositionListener* aListener) = 0;
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/**
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* Internal method used by scrollbars to notify their scrolling
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* container of changes.
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*/
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virtual void CurPosAttributeChanged(nsIContent* aChild) = 0;
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/**
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* Allows the docshell to request that the scroll frame post an event
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* after being restored from history.
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*/
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NS_IMETHOD PostScrolledAreaEventForCurrentArea() = 0;
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/**
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* Returns true if this scrollframe is being "actively scrolled".
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* This basically means that we should allocate resources in the
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* expectation that scrolling is going to happen.
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*/
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virtual bool IsScrollingActive() = 0;
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/**
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* Call this when the layer(s) induced by active scrolling are being
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* completely redrawn.
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*/
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virtual void ResetScrollPositionForLayerPixelAlignment() = 0;
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/**
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* Was the current presentation state for this frame restored from history?
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*/
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virtual bool DidHistoryRestore() = 0;
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/**
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* Clear the flag so that DidHistoryRestore() returns false until the next
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* RestoreState call.
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* @see nsIStatefulFrame::RestoreState
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*/
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virtual void ClearDidHistoryRestore() = 0;
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/**
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* Determine if the passed in rect is nearly visible according to the image
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* visibility heuristics for how close it is to the visible scrollport.
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*/
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virtual bool IsRectNearlyVisible(const nsRect& aRect) = 0;
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/**
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* Returns the origin passed in to the last ScrollToImpl call that took
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* effect.
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*/
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virtual nsIAtom* OriginOfLastScroll() = 0;
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/**
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* Clears the "origin of last scroll" property stored in this frame.
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*/
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virtual void ResetOriginOfLastScroll() = 0;
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};
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#endif
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