gecko-dev/layout/generic/nsIScrollableFrame.h

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