gecko-dev/layout/base/nsChangeHint.h
Ehsan Akhgari bdd1cdb13d Bug 157681 - Part 2: Optimize positioned frame offset changes by moving the frame as opposed to reflowing it in case we know that the size of the frame will not change; r=dbaron
This patch adds a change hint to signal that one of the offsets on a
frame has been changed.  When processing the hint, we do one of the
following things based on the position property of the frame.

* For static frames, we ignore the offset changes completely, as they
  will not change the layout.
* For relative positioned frames, this patch refactors the
  nsHTMLReflowState::ComputeRelativeOffsets function so that it can be
  used from other callers, and it uses that to compute the new relative
  offsets, and uses the offsets computed previously to compute the new
  position of the frame.
* For absolute positioned frames, we set up a fake parent reflow state
  object, and then we create a new reflow state object for the frame in
  question.  This setup is similar to what nsFrame::BoxReflow does.
  Once we have the new reflow state object, we use it to compute the
  absolute offsets, and then we use the computed offsets to set the new
  position of the frame.  The offset computation is similar to what
  nsAbsoluteContainingBlock::ReflowAbsoluteFrame does.  In some cases
  where it is possible for the dimensions of the frame to change based
  on the offset changes, we fall back to a full reflow.
2012-06-06 00:53:48 -04:00

185 lines
6.9 KiB
C

/* -*- 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/. */
/* constants for what needs to be recomputed in response to style changes */
#ifndef nsChangeHint_h___
#define nsChangeHint_h___
#include "prtypes.h"
// Defines for various style related constants
// For hints that don't guarantee that the change will be applied to all descendant
// frames, style structs returning those hints from CalcDifference must have
// their ForceCompare() return true.
enum nsChangeHint {
// change was visual only (e.g., COLOR=)
// Invalidates all descendant frames (including following
// placeholders to out-of-flow frames).
nsChangeHint_RepaintFrame = 0x01,
// For reflow, we want flags to give us arbitrary FrameNeedsReflow behavior.
// just do a FrameNeedsReflow.
nsChangeHint_NeedReflow = 0x02,
// Invalidate intrinsic widths on the frame's ancestors. Must not be set
// without setting nsChangeHint_NeedReflow.
nsChangeHint_ClearAncestorIntrinsics = 0x04,
// Invalidate intrinsic widths on the frame's descendants. Must not be set
// without also setting nsChangeHint_ClearAncestorIntrinsics.
nsChangeHint_ClearDescendantIntrinsics = 0x08,
// Force unconditional reflow of all descendants. Must not be set without
// setting nsChangeHint_NeedReflow, but is independent of both the
// Clear*Intrinsics flags.
nsChangeHint_NeedDirtyReflow = 0x10,
// change requires view to be updated, if there is one (e.g., clip:).
// Updates all descendants (including following placeholders to out-of-flows).
nsChangeHint_SyncFrameView = 0x20,
// The currently shown mouse cursor needs to be updated
nsChangeHint_UpdateCursor = 0x40,
/**
* SVG filter/mask/clip effects need to be recomputed because the URI
* in the filter/mask/clip-path property has changed. This wipes
* out cached nsSVGPropertyBase and subclasses which hold a reference to
* the element referenced by the URI, and a mutation observer for
* the DOM subtree rooted at that element. Also, for filters they store a
* bounding-box for the filter result so that if the filter changes we can
* invalidate the old covered area.
*/
nsChangeHint_UpdateEffects = 0x80,
/**
* Visual change only, but the change can be handled entirely by
* updating the layer(s) for the frame.
* Updates all descendants (including following placeholders to out-of-flows).
*/
nsChangeHint_UpdateOpacityLayer = 0x100,
/**
* Updates all descendants. Any placeholder descendants' out-of-flows
* are also descendants of the transformed frame, so they're updated.
*/
nsChangeHint_UpdateTransformLayer = 0x200,
/**
* Change requires frame change (e.g., display:).
* This subsumes all the above. Reconstructs all frame descendants,
* including following placeholders to out-of-flows.
*/
nsChangeHint_ReconstructFrame = 0x400,
/**
* The frame's effect on its ancestors' overflow areas has changed,
* either through a change in its transform or a change in its position.
* Does not update any descendant frames.
*/
nsChangeHint_UpdateOverflow = 0x800,
/**
* The children-only transform of an SVG frame changed, requiring the
* overflow rects of the frame's immediate children to be updated.
*/
nsChangeHint_ChildrenOnlyTransform = 0x1000,
/**
* The frame's offsets have changed, while its dimensions might have
* changed as well. This hint is used for positioned frames if their
* offset changes. If we decide that the dimensions are likely to
* change, this will trigger a reflow.
*
* Note that this should probably be used in combination with
* nsChangeHint_UpdateOverflow in order to get the overflow areas of
* the ancestors updated as well.
*/
nsChangeHint_RecomputePosition = 0x2000,
/**
* We have an optimization when processing change hints which prevents
* us from visiting the descendants of a node when a hint on that node
* is being processed. This optimization does not apply in some of the
* cases where applying a hint to an element does not necessarily result
* in the same hint being handled on the descendants.
*
* If you're adding such a hint, you should add your hint to this list.
*/
nsChangeHint_NonInherited_Hints =
nsChangeHint_UpdateTransformLayer |
nsChangeHint_UpdateOpacityLayer |
nsChangeHint_UpdateOverflow |
nsChangeHint_ChildrenOnlyTransform |
nsChangeHint_RecomputePosition
};
// Redefine these operators to return nothing. This will catch any use
// of these operators on hints. We should not be using these operators
// on nsChangeHints
inline void operator<(nsChangeHint s1, nsChangeHint s2) {}
inline void operator>(nsChangeHint s1, nsChangeHint s2) {}
inline void operator!=(nsChangeHint s1, nsChangeHint s2) {}
inline void operator==(nsChangeHint s1, nsChangeHint s2) {}
inline void operator<=(nsChangeHint s1, nsChangeHint s2) {}
inline void operator>=(nsChangeHint s1, nsChangeHint s2) {}
// Operators on nsChangeHints
// Merge two hints, taking the union
inline nsChangeHint NS_CombineHint(nsChangeHint aH1, nsChangeHint aH2) {
return (nsChangeHint)(aH1 | aH2);
}
// Merge two hints, taking the union
inline nsChangeHint NS_SubtractHint(nsChangeHint aH1, nsChangeHint aH2) {
return (nsChangeHint)(aH1 & ~aH2);
}
// Merge the "src" hint into the "dst" hint
// Returns true iff the destination changed
inline bool NS_UpdateHint(nsChangeHint& aDest, nsChangeHint aSrc) {
nsChangeHint r = (nsChangeHint)(aDest | aSrc);
bool changed = (int)r != (int)aDest;
aDest = r;
return changed;
}
// Returns true iff the second hint contains all the hints of the first hint
inline bool NS_IsHintSubset(nsChangeHint aSubset, nsChangeHint aSuperSet) {
return (aSubset & aSuperSet) == aSubset;
}
// Redefine the old NS_STYLE_HINT constants in terms of the new hint structure
#define NS_STYLE_HINT_NONE \
nsChangeHint(0)
#define NS_STYLE_HINT_VISUAL \
nsChangeHint(nsChangeHint_RepaintFrame | nsChangeHint_SyncFrameView)
#define nsChangeHint_ReflowFrame \
nsChangeHint(nsChangeHint_NeedReflow | \
nsChangeHint_ClearAncestorIntrinsics | \
nsChangeHint_ClearDescendantIntrinsics | \
nsChangeHint_NeedDirtyReflow)
#define NS_STYLE_HINT_REFLOW \
nsChangeHint(NS_STYLE_HINT_VISUAL | nsChangeHint_ReflowFrame)
#define NS_STYLE_HINT_FRAMECHANGE \
nsChangeHint(NS_STYLE_HINT_REFLOW | nsChangeHint_ReconstructFrame)
/**
* |nsRestyleHint| is a bitfield for the result of
* |HasStateDependentStyle| and |HasAttributeDependentStyle|. When no
* restyling is necessary, use |nsRestyleHint(0)|.
*/
enum nsRestyleHint {
eRestyle_Self = 0x1,
eRestyle_Subtree = 0x2, /* self and descendants */
eRestyle_LaterSiblings = 0x4 /* implies "and descendants" */
};
#endif /* nsChangeHint_h___ */