The Tor Browser: layout/generic/nsIScrollableFrame.h@b8a032363ba2 (annotated)

layout/generic/nsIScrollableFrame.h@b8a032363ba2 (annotated)

layout/generic/nsIScrollableFrame.h

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- 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

The Tor Browser / annotate

layout/generic/nsIScrollableFrame.h@b8a032363ba2 (annotated)

layout/generic/nsIScrollableFrame.h