diff -r 000000000000 -r 6474c204b198 layout/generic/nsIScrollableFrame.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/layout/generic/nsIScrollableFrame.h Wed Dec 31 06:09:35 2014 +0100 @@ -0,0 +1,312 @@ +/* -*- 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 "nsCoord.h" +#include "ScrollbarStyles.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; +class nsPresContext; +class nsIContent; +class nsRenderingContext; +class nsIAtom; + +/** + * 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; + + /** + * 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 mozilla::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; + /** + * Get the element resolution. + */ + virtual gfxSize GetResolution() const = 0; + /** + * Set the element resolution. + */ + virtual void SetResolution(const gfxSize& aResolution) = 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 }; + /** + * @note This method might destroy the frame, pres shell and other objects. + * 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; + /** + * @note This method might destroy the frame, pres shell and other objects. + * 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; + /** + * @note This method might destroy the frame, pres shell and other objects. + * 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, + nsIAtom *aOrigin = nullptr) = 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 }; + /** + * @note This method might destroy the frame, pres shell and other objects. + * 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; + /** + * @note This method might destroy the frame, pres shell and other objects. + * 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; + /** + * Returns true if the scrollframe is currently processing an async + * or smooth scroll. + */ + virtual bool IsProcessingAsyncScroll() = 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() const = 0; + /** + * Was the current resolution set by the user or just default initialized? + */ + virtual bool IsResolutionSet() const = 0; + /** + * Clear the flag so that DidHistoryRestore() returns false until the next + * RestoreState call. + * @see nsIStatefulFrame::RestoreState + */ + virtual void ClearDidHistoryRestore() = 0; + /** + * Determine if the passed in rect is nearly visible according to the image + * visibility heuristics for how close it is to the visible scrollport. + */ + virtual bool IsRectNearlyVisible(const nsRect& aRect) = 0; + /** + * Returns the origin passed in to the last ScrollToImpl call that took + * effect. + */ + virtual nsIAtom* OriginOfLastScroll() = 0; + /** + * Returns the current generation counter for the scroll. This counter + * increments every time the scroll position is set. + */ + virtual uint32_t CurrentScrollGeneration() = 0; + /** + * Clears the "origin of last scroll" property stored in this frame, if + * the generation counter passed in matches the current scroll generation + * counter. + */ + virtual void ResetOriginIfScrollAtGeneration(uint32_t aGeneration) = 0; + /** + * Determine whether it is desirable to be able to asynchronously scroll this + * scroll frame. + */ + virtual bool WantAsyncScroll() const = 0; +}; + +#endif