gecko-dev/layout/generic/nsIScrollableFrame.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/*
* 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 "nsIFrame.h" // to get nsIBox, which is a typedef
class nsBoxLayoutState;
class nsIScrollPositionListener;
/**
* 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 nsQueryFrame {
public:
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 PRUint32 GetScrollbarVisibility() const = 0;
/**
* 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,
nsIRenderingContext* aRC) = 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;
/**
* 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;
/**
* 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.
*/
virtual void ScrollTo(nsPoint aScrollPosition, ScrollMode aMode) = 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 = nsnull) = 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;
/**
* Obtain the XUL box for the horizontal or vertical scrollbar, or null
* if there is no such box. Avoid using this, but may be useful for
* setting up a scrollbar mediator if you want to redirect scrollbar
* input.
*/
virtual nsIBox* GetScrollbarBox(PRBool aVertical) = 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 PRBool IsScrollingActive() = 0;
};
#endif