StickyScrollContainer.cpp
/* -*- 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/. */
/**
* compute sticky positioning, both during reflow and when the scrolling
* container scrolls
*/
#include "StickyScrollContainer.h"
#include "mozilla/OverflowChangedTracker.h"
#include "nsIFrame.h"
#include "nsIFrameInlines.h"
#include "nsIScrollableFrame.h"
#include "nsLayoutUtils.h"
namespace mozilla {
NS_DECLARE_FRAME_PROPERTY_DELETABLE(StickyScrollContainerProperty,
StickyScrollContainer)
StickyScrollContainer::StickyScrollContainer(nsIScrollableFrame* aScrollFrame)
: mScrollFrame(aScrollFrame), mScrollPosition() {
mScrollFrame->AddScrollPositionListener(this);
}
StickyScrollContainer::~StickyScrollContainer() {
mScrollFrame->RemoveScrollPositionListener(this);
}
// static
StickyScrollContainer* StickyScrollContainer::GetStickyScrollContainerForFrame(
nsIFrame* aFrame) {
nsIScrollableFrame* scrollFrame = nsLayoutUtils::GetNearestScrollableFrame(
aFrame->GetParent(), nsLayoutUtils::SCROLLABLE_SAME_DOC |
nsLayoutUtils::SCROLLABLE_STOP_AT_PAGE |
nsLayoutUtils::SCROLLABLE_INCLUDE_HIDDEN);
if (!scrollFrame) {
// We might not find any, for instance in the case of
// <html style="position: fixed">
return nullptr;
}
nsIFrame* frame = do_QueryFrame(scrollFrame);
StickyScrollContainer* s =
frame->GetProperty(StickyScrollContainerProperty());
if (!s) {
s = new StickyScrollContainer(scrollFrame);
frame->SetProperty(StickyScrollContainerProperty(), s);
}
return s;
}
// static
void StickyScrollContainer::NotifyReparentedFrameAcrossScrollFrameBoundary(
nsIFrame* aFrame, nsIFrame* aOldParent) {
nsIScrollableFrame* oldScrollFrame = nsLayoutUtils::GetNearestScrollableFrame(
aOldParent, nsLayoutUtils::SCROLLABLE_SAME_DOC |
nsLayoutUtils::SCROLLABLE_INCLUDE_HIDDEN);
if (!oldScrollFrame) {
// XXX maybe aFrame has sticky descendants that can be sticky now, but
// we aren't going to handle that.
return;
}
StickyScrollContainer* oldSSC =
static_cast<nsIFrame*>(do_QueryFrame(oldScrollFrame))
->GetProperty(StickyScrollContainerProperty());
if (!oldSSC) {
// aOldParent had no sticky descendants, so aFrame doesn't have any sticky
// descendants, and we're done here.
return;
}
auto i = oldSSC->mFrames.Length();
while (i-- > 0) {
nsIFrame* f = oldSSC->mFrames[i];
StickyScrollContainer* newSSC = GetStickyScrollContainerForFrame(f);
if (newSSC != oldSSC) {
oldSSC->RemoveFrame(f);
if (newSSC) {
newSSC->AddFrame(f);
}
}
}
}
// static
StickyScrollContainer*
StickyScrollContainer::GetStickyScrollContainerForScrollFrame(
nsIFrame* aFrame) {
return aFrame->GetProperty(StickyScrollContainerProperty());
}
static nscoord ComputeStickySideOffset(
Side aSide, const StyleRect<LengthPercentageOrAuto>& aOffset,
nscoord aPercentBasis) {
auto& side = aOffset.Get(aSide);
if (side.IsAuto()) {
return NS_AUTOOFFSET;
}
return nsLayoutUtils::ComputeCBDependentValue(aPercentBasis, side);
}
// static
void StickyScrollContainer::ComputeStickyOffsets(nsIFrame* aFrame) {
nsIScrollableFrame* scrollableFrame =
nsLayoutUtils::GetNearestScrollableFrame(
aFrame->GetParent(), nsLayoutUtils::SCROLLABLE_SAME_DOC |
nsLayoutUtils::SCROLLABLE_INCLUDE_HIDDEN);
if (!scrollableFrame) {
// Bail.
return;
}
nsSize scrollContainerSize = scrollableFrame->GetScrolledFrame()
->GetContentRectRelativeToSelf()
.Size();
nsMargin computedOffsets;
const nsStylePosition* position = aFrame->StylePosition();
computedOffsets.left = ComputeStickySideOffset(eSideLeft, position->mOffset,
scrollContainerSize.width);
computedOffsets.right = ComputeStickySideOffset(eSideRight, position->mOffset,
scrollContainerSize.width);
computedOffsets.top = ComputeStickySideOffset(eSideTop, position->mOffset,
scrollContainerSize.height);
computedOffsets.bottom = ComputeStickySideOffset(
eSideBottom, position->mOffset, scrollContainerSize.height);
// Store the offset
nsMargin* offsets = aFrame->GetProperty(nsIFrame::ComputedOffsetProperty());
if (offsets) {
*offsets = computedOffsets;
} else {
aFrame->SetProperty(nsIFrame::ComputedOffsetProperty(),
new nsMargin(computedOffsets));
}
}
static nscoord gUnboundedNegative = nscoord_MIN / 2;
static nscoord gUnboundedExtent = nscoord_MAX;
static nscoord gUnboundedPositive = gUnboundedNegative + gUnboundedExtent;
void StickyScrollContainer::ComputeStickyLimits(nsIFrame* aFrame,
nsRect* aStick,
nsRect* aContain) const {
NS_ASSERTION(nsLayoutUtils::IsFirstContinuationOrIBSplitSibling(aFrame),
"Can't sticky position individual continuations");
aStick->SetRect(gUnboundedNegative, gUnboundedNegative, gUnboundedExtent,
gUnboundedExtent);
aContain->SetRect(gUnboundedNegative, gUnboundedNegative, gUnboundedExtent,
gUnboundedExtent);
const nsMargin* computedOffsets =
aFrame->GetProperty(nsIFrame::ComputedOffsetProperty());
if (!computedOffsets) {
// We haven't reflowed the scroll frame yet, so offsets haven't been
// computed. Bail.
return;
}
nsIFrame* scrolledFrame = mScrollFrame->GetScrolledFrame();
nsIFrame* cbFrame = aFrame->GetContainingBlock();
NS_ASSERTION(cbFrame == scrolledFrame ||
nsLayoutUtils::IsProperAncestorFrame(scrolledFrame, cbFrame),
"Scroll frame should be an ancestor of the containing block");
nsRect rect =
nsLayoutUtils::GetAllInFlowRectsUnion(aFrame, aFrame->GetParent());
// FIXME(bug 1421660): Table row groups aren't supposed to be containing
// blocks, but we treat them as such (maybe it's the right thing to do!).
// Anyway, not having this basically disables position: sticky on table cells,
// which would be really unfortunate, and doesn't match what other browsers
// do.
if (cbFrame != scrolledFrame && cbFrame->IsTableRowGroupFrame()) {
cbFrame = cbFrame->GetContainingBlock();
}
// Containing block limits for the position of aFrame relative to its parent.
// The margin box of the sticky element stays within the content box of the
// contaning-block element.
if (cbFrame == scrolledFrame) {
// cbFrame is the scrolledFrame, and it won't have continuations. Unlike the
// else clause, we consider scrollable overflow rect because and the union
// of its in-flow rects doesn't include the scrollable overflow area.
*aContain = cbFrame->ScrollableOverflowRectRelativeToSelf();
nsLayoutUtils::TransformRect(cbFrame, aFrame->GetParent(), *aContain);
} else {
*aContain = nsLayoutUtils::GetAllInFlowRectsUnion(
cbFrame, aFrame->GetParent(), nsLayoutUtils::RECTS_USE_CONTENT_BOX);
}
nsRect marginRect = nsLayoutUtils::GetAllInFlowRectsUnion(
aFrame, aFrame->GetParent(), nsLayoutUtils::RECTS_USE_MARGIN_BOX);
// Deflate aContain by the difference between the union of aFrame's
// continuations' margin boxes and the union of their border boxes, so that
// by keeping aFrame within aContain, we keep the union of the margin boxes
// within the containing block's content box.
aContain->Deflate(marginRect - rect);
// Deflate aContain by the border-box size, to form a constraint on the
// upper-left corner of aFrame and continuations.
aContain->Deflate(nsMargin(0, rect.width, rect.height, 0));
nsMargin sfPadding = scrolledFrame->GetUsedPadding();
nsPoint sfOffset = aFrame->GetParent()->GetOffsetTo(scrolledFrame);
// Top
if (computedOffsets->top != NS_AUTOOFFSET) {
aStick->SetTopEdge(mScrollPosition.y + sfPadding.top +
computedOffsets->top - sfOffset.y);
}
nsSize sfSize = scrolledFrame->GetContentRectRelativeToSelf().Size();
// Bottom
if (computedOffsets->bottom != NS_AUTOOFFSET &&
(computedOffsets->top == NS_AUTOOFFSET ||
rect.height <= sfSize.height - computedOffsets->TopBottom())) {
aStick->SetBottomEdge(mScrollPosition.y + sfPadding.top + sfSize.height -
computedOffsets->bottom - rect.height - sfOffset.y);
}
StyleDirection direction = cbFrame->StyleVisibility()->mDirection;
// Left
if (computedOffsets->left != NS_AUTOOFFSET &&
(computedOffsets->right == NS_AUTOOFFSET ||
direction == StyleDirection::Ltr ||
rect.width <= sfSize.width - computedOffsets->LeftRight())) {
aStick->SetLeftEdge(mScrollPosition.x + sfPadding.left +
computedOffsets->left - sfOffset.x);
}
// Right
if (computedOffsets->right != NS_AUTOOFFSET &&
(computedOffsets->left == NS_AUTOOFFSET ||
direction == StyleDirection::Rtl ||
rect.width <= sfSize.width - computedOffsets->LeftRight())) {
aStick->SetRightEdge(mScrollPosition.x + sfPadding.left + sfSize.width -
computedOffsets->right - rect.width - sfOffset.x);
}
// These limits are for the bounding box of aFrame's continuations. Convert
// to limits for aFrame itself.
nsPoint frameOffset = aFrame->GetPosition() - rect.TopLeft();
aStick->MoveBy(frameOffset);
aContain->MoveBy(frameOffset);
}
nsPoint StickyScrollContainer::ComputePosition(nsIFrame* aFrame) const {
nsRect stick;
nsRect contain;
ComputeStickyLimits(aFrame, &stick, &contain);
nsPoint position = aFrame->GetNormalPosition();
// For each sticky direction (top, bottom, left, right), move the frame along
// the appropriate axis, based on the scroll position, but limit this to keep
// the element's margin box within the containing block.
position.y = std::max(position.y, std::min(stick.y, contain.YMost()));
position.y = std::min(position.y, std::max(stick.YMost(), contain.y));
position.x = std::max(position.x, std::min(stick.x, contain.XMost()));
position.x = std::min(position.x, std::max(stick.XMost(), contain.x));
return position;
}
bool StickyScrollContainer::IsStuckInYDirection(nsIFrame* aFrame) const {
nsPoint position = ComputePosition(aFrame);
return position.y != aFrame->GetNormalPosition().y;
}
void StickyScrollContainer::GetScrollRanges(nsIFrame* aFrame,
nsRectAbsolute* aOuter,
nsRectAbsolute* aInner) const {
// We need to use the first in flow; continuation frames should not move
// relative to each other and should get identical scroll ranges.
// Also, ComputeStickyLimits requires this.
nsIFrame* firstCont =
nsLayoutUtils::FirstContinuationOrIBSplitSibling(aFrame);
nsRect stickRect;
nsRect containRect;
ComputeStickyLimits(firstCont, &stickRect, &containRect);
nsRectAbsolute stick = nsRectAbsolute::FromRect(stickRect);
nsRectAbsolute contain = nsRectAbsolute::FromRect(containRect);
aOuter->SetBox(gUnboundedNegative, gUnboundedNegative, gUnboundedPositive,
gUnboundedPositive);
aInner->SetBox(gUnboundedNegative, gUnboundedNegative, gUnboundedPositive,
gUnboundedPositive);
const nsPoint normalPosition = firstCont->GetNormalPosition();
// Bottom and top
if (stick.YMost() != gUnboundedPositive) {
aOuter->SetTopEdge(contain.Y() - stick.YMost());
aInner->SetTopEdge(normalPosition.y - stick.YMost());
}
if (stick.Y() != gUnboundedNegative) {
aInner->SetBottomEdge(normalPosition.y - stick.Y());
aOuter->SetBottomEdge(contain.YMost() - stick.Y());
}
// Right and left
if (stick.XMost() != gUnboundedPositive) {
aOuter->SetLeftEdge(contain.X() - stick.XMost());
aInner->SetLeftEdge(normalPosition.x - stick.XMost());
}
if (stick.X() != gUnboundedNegative) {
aInner->SetRightEdge(normalPosition.x - stick.X());
aOuter->SetRightEdge(contain.XMost() - stick.X());
}
// Make sure |inner| does not extend outside of |outer|. (The consumers of
// the Layers API, to which this information is propagated, expect this
// invariant to hold.) The calculated value of |inner| can sometimes extend
// outside of |outer|, for example due to margin collapsing, since
// GetNormalPosition() returns the actual position after margin collapsing,
// while |contain| is calculated based on the frame's GetUsedMargin() which
// is pre-collapsing.
// Note that this doesn't necessarily solve all problems stemming from
// comparing pre- and post-collapsing margins (TODO: find a proper solution).
*aInner = aInner->Intersect(*aOuter);
if (aInner->IsEmpty()) {
// This might happen if aInner didn't intersect aOuter at all initially,
// in which case aInner is empty and outside aOuter. Make sure it doesn't
// extend outside aOuter.
*aInner = aInner->MoveInsideAndClamp(*aOuter);
}
}
void StickyScrollContainer::PositionContinuations(nsIFrame* aFrame) {
NS_ASSERTION(nsLayoutUtils::IsFirstContinuationOrIBSplitSibling(aFrame),
"Should be starting from the first continuation");
bool hadProperty;
nsPoint translation =
ComputePosition(aFrame) - aFrame->GetNormalPosition(&hadProperty);
if (NS_WARN_IF(!hadProperty)) {
// If the frame was never relatively positioned, don't move its position
// dynamically. There are a variety of frames for which `position` doesn't
// really apply like frames inside svg which would get here and be sticky
// only in one direction.
return;
}
// Move all continuation frames by the same amount.
for (nsIFrame* cont = aFrame; cont;
cont = nsLayoutUtils::GetNextContinuationOrIBSplitSibling(cont)) {
cont->SetPosition(cont->GetNormalPosition() + translation);
}
}
void StickyScrollContainer::UpdatePositions(nsPoint aScrollPosition,
nsIFrame* aSubtreeRoot) {
#ifdef DEBUG
{
nsIFrame* scrollFrameAsFrame = do_QueryFrame(mScrollFrame);
NS_ASSERTION(!aSubtreeRoot || aSubtreeRoot == scrollFrameAsFrame,
"If reflowing, should be reflowing the scroll frame");
}
#endif
mScrollPosition = aScrollPosition;
OverflowChangedTracker oct;
oct.SetSubtreeRoot(aSubtreeRoot);
for (nsTArray<nsIFrame*>::size_type i = 0; i < mFrames.Length(); i++) {
nsIFrame* f = mFrames[i];
if (!nsLayoutUtils::IsFirstContinuationOrIBSplitSibling(f)) {
// This frame was added in nsIFrame::Init before we knew it wasn't
// the first ib-split-sibling.
mFrames.RemoveElementAt(i);
--i;
continue;
}
if (aSubtreeRoot) {
// Reflowing the scroll frame, so recompute offsets.
ComputeStickyOffsets(f);
}
// mFrames will only contain first continuations, because we filter in
// nsIFrame::Init.
PositionContinuations(f);
f = f->GetParent();
if (f != aSubtreeRoot) {
for (nsIFrame* cont = f; cont;
cont = nsLayoutUtils::GetNextContinuationOrIBSplitSibling(cont)) {
oct.AddFrame(cont, OverflowChangedTracker::CHILDREN_CHANGED);
}
}
}
oct.Flush();
}
void StickyScrollContainer::ScrollPositionWillChange(nscoord aX, nscoord aY) {}
void StickyScrollContainer::ScrollPositionDidChange(nscoord aX, nscoord aY) {
UpdatePositions(nsPoint(aX, aY), nullptr);
}
} // namespace mozilla
