gecko-dev/layout/generic/ScrollAnchorContainer.cpp

599 строки
22 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */
#include "ScrollAnchorContainer.h"
#include "GeckoProfiler.h"
#include "mozilla/dom/Text.h"
#include "mozilla/StaticPrefs.h"
#include "mozilla/ToString.h"
#include "nsGfxScrollFrame.h"
#include "nsLayoutUtils.h"
#define ANCHOR_LOG(...)
// #define ANCHOR_LOG(...) printf_stderr("ANCHOR: " __VA_ARGS__)
namespace mozilla {
namespace layout {
ScrollAnchorContainer::ScrollAnchorContainer(ScrollFrameHelper* aScrollFrame)
: mScrollFrame(aScrollFrame),
mAnchorNode(nullptr),
mLastAnchorOffset(0),
mAnchorNodeIsDirty(true),
mApplyingAnchorAdjustment(false),
mSuppressAnchorAdjustment(false) {}
ScrollAnchorContainer::~ScrollAnchorContainer() {}
ScrollAnchorContainer* ScrollAnchorContainer::FindFor(nsIFrame* aFrame) {
aFrame = aFrame->GetParent();
if (!aFrame) {
return nullptr;
}
nsIScrollableFrame* nearest = nsLayoutUtils::GetNearestScrollableFrame(
aFrame, nsLayoutUtils::SCROLLABLE_SAME_DOC |
nsLayoutUtils::SCROLLABLE_INCLUDE_HIDDEN);
if (nearest) {
return nearest->Anchor();
}
return nullptr;
}
nsIFrame* ScrollAnchorContainer::Frame() const { return mScrollFrame->mOuter; }
nsIScrollableFrame* ScrollAnchorContainer::ScrollableFrame() const {
return Frame()->GetScrollTargetFrame();
}
/**
* Set the appropriate frame flags for a frame that has become or is no longer
* an anchor node.
*/
static void SetAnchorFlags(const nsIFrame* aScrolledFrame,
nsIFrame* aAnchorNode, bool aInScrollAnchorChain) {
nsIFrame* frame = aAnchorNode;
while (frame && frame != aScrolledFrame) {
MOZ_ASSERT(
frame == aAnchorNode || !frame->IsScrollFrame(),
"We shouldn't select an anchor node inside a nested scroll frame.");
frame->SetInScrollAnchorChain(aInScrollAnchorChain);
frame = frame->GetParent();
}
MOZ_ASSERT(frame,
"The anchor node should be a descendant of the scroll frame");
// If needed, invalidate the frame so that we start/stop highlighting the
// anchor
if (StaticPrefs::layout_css_scroll_anchoring_highlight()) {
for (nsIFrame* frame = aAnchorNode->FirstContinuation(); !!frame;
frame = frame->GetNextContinuation()) {
frame->InvalidateFrame();
}
}
}
/**
* Compute the scrollable overflow rect [1] of aCandidate relative to
* aScrollFrame with all transforms applied.
*
* The specification is ambiguous about what can be selected as a scroll anchor,
* which makes the scroll anchoring bounding rect partially undefined [2]. This
* code attempts to match the implementation in Blink.
*
* An additional unspecified behavior is that any scrollable overflow before the
* border start edge in the block axis of aScrollFrame should be clamped. This
* is to prevent absolutely positioned descendant elements from being able to
* trigger scroll adjustments [3].
*
* [1]
* https://drafts.csswg.org/css-scroll-anchoring-1/#scroll-anchoring-bounding-rect
* [2] https://github.com/w3c/csswg-drafts/issues/3478
* [3] https://bugzilla.mozilla.org/show_bug.cgi?id=1519541
*/
static nsRect FindScrollAnchoringBoundingRect(const nsIFrame* aScrollFrame,
nsIFrame* aCandidate) {
MOZ_ASSERT(nsLayoutUtils::IsProperAncestorFrame(aScrollFrame, aCandidate));
if (!!Text::FromNodeOrNull(aCandidate->GetContent())) {
// This is a frame for a text node. The spec says we need to accumulate the
// union of all line boxes in the coordinate space of the scroll frame
// accounting for transforms.
//
// To do this, we translate and accumulate the overflow rect for each text
// continuation to the coordinate space of the nearest ancestor block
// frame. Then we transform the resulting rect into the coordinate space of
// the scroll frame.
//
// Transforms aren't allowed on non-replaced inline boxes, so we can assume
// that these text node continuations will have the same transform as their
// nearest block ancestor. And it should be faster to transform their union
// rather than individually transforming each overflow rect
//
// XXX for fragmented blocks, blockAncestor will be an ancestor only to the
// text continuations in the first block continuation. GetOffsetTo
// should continue to work, but is it correct with transforms or a
// performance hazard?
nsIFrame* blockAncestor =
nsLayoutUtils::FindNearestBlockAncestor(aCandidate);
MOZ_ASSERT(
nsLayoutUtils::IsProperAncestorFrame(aScrollFrame, blockAncestor));
nsRect bounding;
for (nsIFrame* continuation = aCandidate->FirstContinuation(); continuation;
continuation = continuation->GetNextContinuation()) {
nsRect overflowRect =
continuation->GetScrollableOverflowRectRelativeToSelf();
overflowRect += continuation->GetOffsetTo(blockAncestor);
bounding = bounding.Union(overflowRect);
}
return nsLayoutUtils::TransformFrameRectToAncestor(blockAncestor, bounding,
aScrollFrame);
}
nsRect borderRect = aCandidate->GetRectRelativeToSelf();
nsRect overflowRect = aCandidate->GetScrollableOverflowRectRelativeToSelf();
NS_ASSERTION(overflowRect.Contains(borderRect),
"overflow rect must include border rect, and the clamping logic "
"here depends on that");
// Clamp the scrollable overflow rect to the border start edge on the block
// axis of the scroll frame
WritingMode writingMode = aScrollFrame->GetWritingMode();
switch (writingMode.GetBlockDir()) {
case WritingMode::eBlockTB: {
overflowRect.SetBoxY(borderRect.Y(), overflowRect.YMost());
break;
}
case WritingMode::eBlockLR: {
overflowRect.SetBoxX(borderRect.X(), overflowRect.XMost());
break;
}
case WritingMode::eBlockRL: {
overflowRect.SetBoxX(overflowRect.X(), borderRect.XMost());
break;
}
}
nsRect transformed = nsLayoutUtils::TransformFrameRectToAncestor(
aCandidate, overflowRect, aScrollFrame);
return transformed;
}
/**
* Compute the offset between the scrollable overflow rect start edge of
* aCandidate and the scroll-port start edge of aScrollFrame, in the block axis
* of aScrollFrame.
*/
static nscoord FindScrollAnchoringBoundingOffset(
const ScrollFrameHelper* aScrollFrame, nsIFrame* aCandidate) {
WritingMode writingMode = aScrollFrame->mOuter->GetWritingMode();
nsRect physicalBounding =
FindScrollAnchoringBoundingRect(aScrollFrame->mOuter, aCandidate);
LogicalRect logicalBounding(writingMode, physicalBounding,
aScrollFrame->mScrolledFrame->GetSize());
return logicalBounding.BStart(writingMode);
}
void ScrollAnchorContainer::SelectAnchor() {
MOZ_ASSERT(mScrollFrame->mScrolledFrame);
MOZ_ASSERT(mAnchorNodeIsDirty);
if (!StaticPrefs::layout_css_scroll_anchoring_enabled()) {
return;
}
AUTO_PROFILER_LABEL("ScrollAnchorContainer::SelectAnchor", LAYOUT);
ANCHOR_LOG(
"Selecting anchor for %p with scroll-port=%s.\n", this,
mozilla::ToString(mScrollFrame->GetVisualOptimalViewingRect()).c_str());
const nsStyleDisplay* disp = Frame()->StyleDisplay();
// Don't select a scroll anchor if the scroll frame has `overflow-anchor:
// none`.
bool overflowAnchor =
disp->mOverflowAnchor == mozilla::StyleOverflowAnchor::Auto;
// Or if the scroll frame has not been scrolled from the logical origin. This
// is not in the specification [1], but Blink does this.
//
// [1] https://github.com/w3c/csswg-drafts/issues/3319
bool isScrolled = mScrollFrame->GetLogicalScrollPosition() != nsPoint();
// Or if there is perspective that could affect the scrollable overflow rect
// for descendant frames. This is not in the specification as Blink doesn't
// share this behavior with perspective [1].
//
// [1] https://github.com/w3c/csswg-drafts/issues/3322
bool hasPerspective = Frame()->ChildrenHavePerspective();
// Select a new scroll anchor
nsIFrame* oldAnchor = mAnchorNode;
if (overflowAnchor && isScrolled && !hasPerspective) {
ANCHOR_LOG("Beginning candidate selection.\n");
mAnchorNode = FindAnchorIn(mScrollFrame->mScrolledFrame);
} else {
if (!overflowAnchor) {
ANCHOR_LOG("Skipping candidate selection for `overflow-anchor: none`\n");
}
if (!isScrolled) {
ANCHOR_LOG("Skipping candidate selection for not being scrolled\n");
}
if (hasPerspective) {
ANCHOR_LOG(
"Skipping candidate selection for scroll frame with perspective\n");
}
mAnchorNode = nullptr;
}
// Update the anchor flags if needed
if (oldAnchor != mAnchorNode) {
ANCHOR_LOG("Anchor node has changed from (%p) to (%p).\n", oldAnchor,
mAnchorNode);
// Unset all flags for the old scroll anchor
if (oldAnchor) {
SetAnchorFlags(mScrollFrame->mScrolledFrame, oldAnchor, false);
}
// Set all flags for the new scroll anchor
if (mAnchorNode) {
// Anchor selection will never select a descendant of a different scroll
// frame, so we can set flags without conflicting with other scroll
// anchor containers.
SetAnchorFlags(mScrollFrame->mScrolledFrame, mAnchorNode, true);
}
} else {
ANCHOR_LOG("Anchor node has remained (%p).\n", mAnchorNode);
}
// Calculate the position to use for scroll adjustments
if (mAnchorNode) {
mLastAnchorOffset =
FindScrollAnchoringBoundingOffset(mScrollFrame, mAnchorNode);
ANCHOR_LOG("Using last anchor offset = %d.\n", mLastAnchorOffset);
} else {
mLastAnchorOffset = 0;
}
mAnchorNodeIsDirty = false;
}
void ScrollAnchorContainer::UserScrolled() {
if (mApplyingAnchorAdjustment) {
return;
}
InvalidateAnchor();
}
void ScrollAnchorContainer::SuppressAdjustments() {
ANCHOR_LOG("Received a scroll anchor suppression for %p.\n", this);
mSuppressAnchorAdjustment = true;
}
void ScrollAnchorContainer::InvalidateAnchor() {
ANCHOR_LOG("Invalidating scroll anchor %p for %p.\n", mAnchorNode, this);
if (mAnchorNode) {
SetAnchorFlags(mScrollFrame->mScrolledFrame, mAnchorNode, false);
}
mAnchorNode = nullptr;
mAnchorNodeIsDirty = true;
mLastAnchorOffset = 0;
if (!StaticPrefs::layout_css_scroll_anchoring_enabled()) {
return;
}
Frame()->PresShell()->PostPendingScrollAnchorSelection(this);
}
void ScrollAnchorContainer::Destroy() {
if (mAnchorNode) {
SetAnchorFlags(mScrollFrame->mScrolledFrame, mAnchorNode, false);
}
mAnchorNode = nullptr;
mAnchorNodeIsDirty = false;
mLastAnchorOffset = 0;
}
void ScrollAnchorContainer::ApplyAdjustments() {
if (!mAnchorNode || mAnchorNodeIsDirty) {
mSuppressAnchorAdjustment = false;
ANCHOR_LOG("Ignoring post-reflow (anchor=%p, dirty=%d, container=%p).\n",
mAnchorNode, mAnchorNodeIsDirty, this);
return;
}
nscoord current =
FindScrollAnchoringBoundingOffset(mScrollFrame, mAnchorNode);
nscoord logicalAdjustment = current - mLastAnchorOffset;
WritingMode writingMode = Frame()->GetWritingMode();
ANCHOR_LOG("Anchor has moved from %d to %d.\n", mLastAnchorOffset, current);
if (logicalAdjustment == 0) {
ANCHOR_LOG("Ignoring zero delta anchor adjustment for %p.\n", this);
mSuppressAnchorAdjustment = false;
return;
}
if (mSuppressAnchorAdjustment) {
ANCHOR_LOG("Applying anchor adjustment suppression for %p.\n", this);
mSuppressAnchorAdjustment = false;
InvalidateAnchor();
return;
}
ANCHOR_LOG("Applying anchor adjustment of %d in %s for %p and anchor %p.\n",
logicalAdjustment, writingMode.DebugString(), this, mAnchorNode);
nsPoint physicalAdjustment;
switch (writingMode.GetBlockDir()) {
case WritingMode::eBlockTB: {
physicalAdjustment.y = logicalAdjustment;
break;
}
case WritingMode::eBlockLR: {
physicalAdjustment.x = logicalAdjustment;
break;
}
case WritingMode::eBlockRL: {
physicalAdjustment.x = -logicalAdjustment;
break;
}
}
MOZ_ASSERT(!mApplyingAnchorAdjustment);
// We should use AutoRestore here, but that doesn't work with bitfields
mApplyingAnchorAdjustment = true;
mScrollFrame->ScrollTo(mScrollFrame->GetScrollPosition() + physicalAdjustment,
ScrollMode::eInstant, nsGkAtoms::relative);
mApplyingAnchorAdjustment = false;
nsPresContext* pc = Frame()->PresContext();
Document* doc = pc->Document();
doc->UpdateForScrollAnchorAdjustment(logicalAdjustment);
// The anchor position may not be in the same relative position after
// adjustment. Update ourselves so we have consistent state.
mLastAnchorOffset =
FindScrollAnchoringBoundingOffset(mScrollFrame, mAnchorNode);
}
ScrollAnchorContainer::ExamineResult
ScrollAnchorContainer::ExamineAnchorCandidate(nsIFrame* aFrame) const {
#ifdef DEBUG_FRAME_DUMP
nsCString tag = aFrame->ListTag();
ANCHOR_LOG("\tVisiting frame=%s (%p).\n", tag.get(), aFrame);
#else
ANCHOR_LOG("\t\tVisiting frame=%p.\n", aFrame);
#endif
bool isText = !!Text::FromNodeOrNull(aFrame->GetContent());
bool isContinuation = !!aFrame->GetPrevContinuation();
if (isText && isContinuation) {
ANCHOR_LOG("\t\tExcluding continuation text node.\n");
return ExamineResult::Exclude;
}
// Check if the author has opted out of scroll anchoring for this frame
// and its descendants.
const nsStyleDisplay* disp = aFrame->StyleDisplay();
if (disp->mOverflowAnchor == mozilla::StyleOverflowAnchor::None) {
ANCHOR_LOG("\t\tExcluding `overflow-anchor: none`.\n");
return ExamineResult::Exclude;
}
// Sticky positioned elements can move with the scroll frame, making them
// unsuitable scroll anchors. This isn't in the specification yet [1], but
// matches Blink's implementation.
//
// [1] https://github.com/w3c/csswg-drafts/issues/3319
if (aFrame->IsStickyPositioned()) {
ANCHOR_LOG("\t\tExcluding `position: sticky`.\n");
return ExamineResult::Exclude;
}
// The frame for a <br> element has a non-zero area, but Blink treats them
// as if they have no area, so exclude them specially.
if (aFrame->IsBrFrame()) {
ANCHOR_LOG("\t\tExcluding <br>.\n");
return ExamineResult::Exclude;
}
// Exclude frames that aren't accessible to content.
bool isChrome =
aFrame->GetContent() && aFrame->GetContent()->ChromeOnlyAccess();
bool isPseudo = aFrame->Style()->IsPseudoElement();
if (isChrome && !isPseudo) {
ANCHOR_LOG("\t\tExcluding chrome only content.\n");
return ExamineResult::Exclude;
}
// See if this frame could have its own anchor node. We could check
// IsScrollFrame(), but that would miss nsListControlFrame which is not a
// scroll frame, but still inherits from nsHTMLScrollFrame.
nsIScrollableFrame* scrollable = do_QueryFrame(aFrame);
// We don't allow scroll anchors to be selected inside of scrollable frames as
// it's not clear how an anchor adjustment should apply to multiple scrollable
// frames. Blink allows this to happen, but they're not sure why [1].
//
// We also don't allow scroll anchors to be selected inside of SVG as it uses
// a different layout model than CSS, and the specification doesn't say it
// should apply.
//
// [1] https://github.com/w3c/csswg-drafts/issues/3477
bool canDescend = !scrollable && !aFrame->IsSVGOuterSVGFrame();
// Check what kind of frame this is
bool isBlockOutside = aFrame->IsBlockOutside();
bool isAnonBox = aFrame->Style()->IsAnonBox() && !isText;
bool isInlineOutside = aFrame->IsInlineOutside() && !isText;
// If the frame is anonymous or inline-outside, search its descendants for a
// scroll anchor.
if ((isAnonBox || isInlineOutside) && canDescend) {
ANCHOR_LOG(
"\t\tSearching descendants of anon or inline box (a=%d, i=%d).\n",
isAnonBox, isInlineOutside);
return ExamineResult::PassThrough;
}
// If the frame is not block-outside or a text node then exclude it.
if (!isBlockOutside && !isText) {
ANCHOR_LOG("\t\tExcluding non block-outside or text node (b=%d, t=%d).\n",
isBlockOutside, isText);
return ExamineResult::Exclude;
}
// Find the scroll anchoring bounding rect.
nsRect rect = FindScrollAnchoringBoundingRect(Frame(), aFrame);
ANCHOR_LOG("\t\trect = [%d %d x %d %d].\n", rect.x, rect.y, rect.width,
rect.height);
// Check if this frame is visible in the scroll port. This will exclude rects
// with zero sized area. The specification is ambiguous about this [1], but
// this matches Blink's implementation.
//
// [1] https://github.com/w3c/csswg-drafts/issues/3483
nsRect visibleRect;
if (!visibleRect.IntersectRect(rect,
mScrollFrame->GetVisualOptimalViewingRect())) {
return ExamineResult::Exclude;
}
// At this point, if canDescend is true, we should only have visible
// non-anonymous frames that are either:
// 1. block-outside
// 2. text nodes
//
// It's not clear what the scroll anchoring bounding rect of elements that are
// block-outside should be when they are fragmented. For text nodes that are
// fragmented, it's specified that we need to consider the union of its line
// boxes.
//
// So for text nodes we handle them by including the union of line boxes in
// the bounding rect of the primary frame, and not selecting any
// continuations.
//
// For block-outside elements we choose to consider the bounding rect of each
// frame individually, allowing ourselves to descend into any frame, but only
// selecting a frame if it's not a continuation.
if (canDescend && isContinuation) {
ANCHOR_LOG("\t\tSearching descendants of a continuation.\n");
return ExamineResult::PassThrough;
}
// If this frame is fully visible, then select it as the scroll anchor.
if (visibleRect.IsEqualEdges(rect)) {
ANCHOR_LOG("\t\tFully visible, taking.\n");
return ExamineResult::Accept;
}
// If we can't descend into this frame, then select it as the scroll anchor.
if (!canDescend) {
ANCHOR_LOG("\t\tIntersects a frame that we can't descend into, taking.\n");
return ExamineResult::Accept;
}
// It must be partially visible and we can descend into this frame. Examine
// its children for a better scroll anchor or fall back to this one.
ANCHOR_LOG("\t\tIntersects valid candidate, checking descendants.\n");
return ExamineResult::Traverse;
}
nsIFrame* ScrollAnchorContainer::FindAnchorIn(nsIFrame* aFrame) const {
// Visit the child lists of this frame
for (nsIFrame::ChildListIterator lists(aFrame); !lists.IsDone();
lists.Next()) {
// Skip child lists that contain out-of-flow frames, we'll visit them by
// following placeholders in the in-flow lists so that we visit these
// frames in DOM order.
// XXX do we actually need to exclude kOverflowOutOfFlowList too?
if (lists.CurrentID() == FrameChildListID::kAbsoluteList ||
lists.CurrentID() == FrameChildListID::kFixedList ||
lists.CurrentID() == FrameChildListID::kFloatList ||
lists.CurrentID() == FrameChildListID::kOverflowOutOfFlowList) {
continue;
}
// Search the child list, and return if we selected an anchor
if (nsIFrame* anchor = FindAnchorInList(lists.CurrentList())) {
return anchor;
}
}
// The spec requires us to do an extra pass to visit absolutely positioned
// frames a second time after all the children of their containing block have
// been visited.
//
// It's not clear why this is needed [1], but it matches Blink's
// implementation, and is needed for a WPT test.
//
// [1] https://github.com/w3c/csswg-drafts/issues/3465
const nsFrameList& absPosList =
aFrame->GetChildList(FrameChildListID::kAbsoluteList);
if (nsIFrame* anchor = FindAnchorInList(absPosList)) {
return anchor;
}
return nullptr;
}
nsIFrame* ScrollAnchorContainer::FindAnchorInList(
const nsFrameList& aFrameList) const {
for (nsIFrame* child : aFrameList) {
// If this is a placeholder, try to follow it to the out of flow frame.
nsIFrame* realFrame = nsPlaceholderFrame::GetRealFrameFor(child);
if (child != realFrame) {
// If the out of flow frame is not a descendant of our scroll frame,
// then it must have a different containing block and cannot be an
// anchor node.
if (!nsLayoutUtils::IsProperAncestorFrame(Frame(), realFrame)) {
ANCHOR_LOG(
"\t\tSkipping out of flow frame that is not a descendant of the "
"scroll frame.\n");
continue;
}
ANCHOR_LOG("\t\tFollowing placeholder to out of flow frame.\n");
child = realFrame;
}
// Perform the candidate examination algorithm
ExamineResult examine = ExamineAnchorCandidate(child);
// See the comment before the definition of `ExamineResult` in
// `ScrollAnchorContainer.h` for an explanation of this behavior.
switch (examine) {
case ExamineResult::Exclude: {
continue;
}
case ExamineResult::PassThrough: {
nsIFrame* candidate = FindAnchorIn(child);
if (!candidate) {
continue;
}
return candidate;
}
case ExamineResult::Traverse: {
nsIFrame* candidate = FindAnchorIn(child);
if (!candidate) {
return child;
}
return candidate;
}
case ExamineResult::Accept: {
return child;
}
}
}
return nullptr;
}
} // namespace layout
} // namespace mozilla