Source code

Revision control

Copy as Markdown

Other Tools

/* -*- 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 */
#include "APZCCallbackHelper.h"
#include "APZEventState.h" // for PrecedingPointerDown
#include "gfxPlatform.h" // For gfxPlatform::UseTiling
#include "mozilla/AsyncEventDispatcher.h"
#include "mozilla/EventForwards.h"
#include "mozilla/dom/CustomEvent.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/MouseEventBinding.h"
#include "mozilla/dom/BrowserParent.h"
#include "mozilla/dom/ScriptSettings.h"
#include "mozilla/IntegerPrintfMacros.h"
#include "mozilla/layers/RepaintRequest.h"
#include "mozilla/layers/WebRenderLayerManager.h"
#include "mozilla/layers/WebRenderBridgeChild.h"
#include "mozilla/DisplayPortUtils.h"
#include "mozilla/PresShell.h"
#include "mozilla/ScrollContainerFrame.h"
#include "mozilla/ToString.h"
#include "mozilla/ViewportUtils.h"
#include "nsContainerFrame.h"
#include "nsContentUtils.h"
#include "nsIContent.h"
#include "nsIDOMWindowUtils.h"
#include "mozilla/dom/Document.h"
#include "nsIInterfaceRequestorUtils.h"
#include "nsLayoutUtils.h"
#include "nsPrintfCString.h"
#include "nsPIDOMWindow.h"
#include "nsRefreshDriver.h"
#include "nsString.h"
#include "nsView.h"
static mozilla::LazyLogModule sApzHlpLog("apz.helper");
#define APZCCH_LOG(...) MOZ_LOG(sApzHlpLog, LogLevel::Debug, (__VA_ARGS__))
static mozilla::LazyLogModule sDisplayportLog("apz.displayport");
namespace mozilla {
namespace layers {
using dom::BrowserParent;
uint64_t APZCCallbackHelper::sLastTargetAPZCNotificationInputBlock =
static ScreenMargin RecenterDisplayPort(const ScreenMargin& aDisplayPort) {
ScreenMargin margins = aDisplayPort;
margins.right = margins.left = margins.LeftRight() / 2; = margins.bottom = margins.TopBottom() / 2;
return margins;
static PresShell* GetPresShell(const nsIContent* aContent) {
if (dom::Document* doc = aContent->GetComposedDoc()) {
return doc->GetPresShell();
return nullptr;
static CSSPoint ScrollFrameTo(ScrollContainerFrame* aFrame,
const RepaintRequest& aRequest,
bool& aSuccessOut) {
aSuccessOut = false;
CSSPoint targetScrollPosition = aRequest.GetLayoutScrollOffset();
if (!aFrame) {
return targetScrollPosition;
CSSPoint geckoScrollPosition =
// If the repaint request was triggered due to a previous main-thread scroll
// offset update sent to the APZ, then we don't need to do another scroll here
// and we can just return.
if (!aRequest.GetScrollOffsetUpdated()) {
return geckoScrollPosition;
// If this frame is overflow:hidden, then the expectation is that it was
// sized in a way that respects its scrollable boundaries. For the root
// frame, this means that it cannot be scrolled in such a way that it moves
// the layout viewport. For a non-root frame, this means that it cannot be
// scrolled at all.
// In either case, |targetScrollPosition| should be the same as
// |geckoScrollPosition| here.
// However, this is slightly racy. We query the overflow property of the
// scroll frame at the time the repaint request arrives at the main thread
// (i.e., right now), but APZ made the decision of whether or not to allow
// scrolling based on the information it had at the time it processed the
// scroll event. The overflow property could have changed at some time
// between the two events and so APZ may have computed a scrollable region
// that is larger than what is actually allowed.
// Currently, we allow the scroll position to change even though the frame is
// overflow:hidden (that is, we take |targetScrollPosition|). If this turns
// out to be problematic, an alternative solution would be to ignore the
// scroll position change (that is, use |geckoScrollPosition|).
if (aFrame->GetScrollStyles().mVertical == StyleOverflow::Hidden &&
targetScrollPosition.y != geckoScrollPosition.y) {
"APZCCH: targetScrollPosition.y (%f) != geckoScrollPosition.y (%f)",
targetScrollPosition.y.value, geckoScrollPosition.y.value)
if (aFrame->GetScrollStyles().mHorizontal == StyleOverflow::Hidden &&
targetScrollPosition.x != geckoScrollPosition.x) {
"APZCCH: targetScrollPosition.x (%f) != geckoScrollPosition.x (%f)",
targetScrollPosition.x.value, geckoScrollPosition.x.value)
// If the scrollable frame is currently in the middle of an async or smooth
// scroll then we don't want to interrupt it (see bug 961280).
// Also if the scrollable frame got a scroll request from a higher priority
// origin since the last layers update, then we don't want to push our scroll
// request because we'll clobber that one, which is bad.
bool scrollInProgress = APZCCallbackHelper::IsScrollInProgress(aFrame);
if (!scrollInProgress) {
ScrollSnapTargetIds snapTargetIds = aRequest.GetLastSnapTargetIds();
geckoScrollPosition = CSSPoint::FromAppUnits(aFrame->GetScrollPosition());
aSuccessOut = true;
// Return the final scroll position after setting it so that anything that
// relies on it can have an accurate value. Note that even if we set it above
// re-querying it is a good idea because it may have gotten clamped or
// rounded.
return geckoScrollPosition;
* Scroll the scroll frame associated with |aContent| to the scroll position
* requested in |aRequest|.
* Any difference between the requested and actual scroll positions is used to
* update the callback-transform stored on the content, and return a new
* display port.
static DisplayPortMargins ScrollFrame(nsIContent* aContent,
const RepaintRequest& aRequest) {
// Scroll the window to the desired spot
ScrollContainerFrame* sf =
if (sf) {
if (sf->IsRootScrollFrameOfDocument()) {
if (!APZCCallbackHelper::IsScrollInProgress(sf)) {
APZCCH_LOG("Setting VV offset to %s\n",
if (sf->SetVisualViewportOffset(
/* aRepaint = */ false)) {
// sf can't be destroyed if SetVisualViewportOffset returned true.
// sf might have been destroyed by the call to SetVisualViewportOffset, so
// re-get it.
sf = nsLayoutUtils::FindScrollContainerFrameFor(aRequest.GetScrollId());
bool scrollUpdated = false;
auto displayPortMargins = DisplayPortMargins::ForScrollContainerFrame(
sf, aRequest.GetDisplayPortMargins());
CSSPoint apzScrollOffset = aRequest.GetVisualScrollOffset();
CSSPoint actualScrollOffset = ScrollFrameTo(sf, aRequest, scrollUpdated);
CSSPoint scrollDelta = apzScrollOffset - actualScrollOffset;
if (scrollUpdated) {
if (aRequest.IsScrollInfoLayer()) {
// In cases where the APZ scroll offset is different from the content
// scroll offset, we want to interpret the margins as relative to the APZ
// scroll offset except when the frame is not scrollable by APZ.
// Therefore, if the layer is a scroll info layer, we leave the margins
// as-is and they will be interpreted as relative to the content scroll
// offset.
if (nsIFrame* frame = aContent->GetPrimaryFrame()) {
} else {
// Correct the display port due to the difference between the requested
// and actual scroll offsets.
displayPortMargins =
apzScrollOffset, actualScrollOffset);
} else if (aRequest.IsRootContent() &&
apzScrollOffset != aRequest.GetLayoutScrollOffset()) {
// APZ uses the visual viewport's offset to calculate where to place the
// display port, so the display port is misplaced when a pinch zoom occurs.
// We need to force a display port adjustment in the following paint to
// account for a difference between the requested and actual scroll
// offsets in repaints requested by
// AsyncPanZoomController::NotifyLayersUpdated.
displayPortMargins = DisplayPortMargins::FromAPZ(
aRequest.GetDisplayPortMargins(), apzScrollOffset, actualScrollOffset);
} else {
// For whatever reason we couldn't update the scroll offset on the scroll
// frame, which means the data APZ used for its displayport calculation is
// stale. Fall back to a sane default behaviour. Note that we don't
// tile-align the recentered displayport because tile-alignment depends on
// the scroll position, and the scroll position here is out of our control.
// See bug 966507 comment 21 for a more detailed explanation.
displayPortMargins = DisplayPortMargins::ForScrollContainerFrame(
sf, RecenterDisplayPort(aRequest.GetDisplayPortMargins()));
// APZ transforms inputs assuming we applied the exact scroll offset it
// requested (|apzScrollOffset|). Since we may not have, record the difference
// between what APZ asked for and what we actually applied, and apply it to
// input events to compensate.
// Note that if the main-thread had a change in its scroll position, we don't
// want to record that difference here, because it can be large and throw off
// input events by a large amount. It is also going to be transient, because
// any main-thread scroll position change will be synced to APZ and we will
// get another repaint request when APZ confirms. In the interval while this
// is happening we can just leave the callback transform as it was.
bool mainThreadScrollChanged =
sf && sf->CurrentScrollGeneration() != aRequest.GetScrollGeneration() &&
if (aContent && !mainThreadScrollChanged) {
new CSSPoint(scrollDelta),
return displayPortMargins;
static void SetDisplayPortMargins(PresShell* aPresShell, nsIContent* aContent,
const DisplayPortMargins& aDisplayPortMargins,
CSSSize aDisplayPortBase) {
if (!aContent) {
bool hadDisplayPort = DisplayPortUtils::HasDisplayPort(aContent);
if (MOZ_LOG_TEST(sDisplayportLog, LogLevel::Debug)) {
if (!hadDisplayPort) {
mozilla::layers::ScrollableLayerGuid::ViewID viewID =
nsLayoutUtils::FindIDFor(aContent, &viewID);
sDisplayportLog, LogLevel::Debug,
("APZCCH installing displayport margins %s on scrollId=%" PRIu64 "\n",
ToString(aDisplayPortMargins).c_str(), viewID));
aContent, aPresShell, aDisplayPortMargins,
hadDisplayPort ? DisplayPortUtils::ClearMinimalDisplayPortProperty::No
: DisplayPortUtils::ClearMinimalDisplayPortProperty::Yes,
if (!hadDisplayPort) {
nsRect base(0, 0, aDisplayPortBase.width * AppUnitsPerCSSPixel(),
aDisplayPortBase.height * AppUnitsPerCSSPixel());
DisplayPortUtils::SetDisplayPortBaseIfNotSet(aContent, base);
static void SetPaintRequestTime(nsIContent* aContent,
const TimeStamp& aPaintRequestTime) {
new TimeStamp(aPaintRequestTime),
void APZCCallbackHelper::NotifyLayerTransforms(
const nsTArray<MatrixMessage>& aTransforms) {
for (const MatrixMessage& msg : aTransforms) {
BrowserParent* parent =
if (parent) {
void APZCCallbackHelper::UpdateRootFrame(const RepaintRequest& aRequest) {
if (aRequest.GetScrollId() == ScrollableLayerGuid::NULL_SCROLL_ID) {
RefPtr<nsIContent> content =
if (!content) {
RefPtr<PresShell> presShell = GetPresShell(content);
if (!presShell || aRequest.GetPresShellId() != presShell->GetPresShellId()) {
APZCCH_LOG("Handling request %s\n", ToString(aRequest).c_str());
if (nsLayoutUtils::AllowZoomingForDocument(presShell->GetDocument()) &&
aRequest.GetAsyncZoom().scale != 1.0) {
// If zooming is disabled then we don't really want to let APZ fiddle
// with these things. In theory setting the resolution here should be a
// no-op, but setting the visual viewport size is bad because it can cause a
// stale value to be returned by window.innerWidth/innerHeight (see bug
// 1187792).
float presShellResolution = presShell->GetResolution();
// If the pres shell resolution has changed on the content side side
// the time this repaint request was fired, consider this request out of
// date and drop it; setting a zoom based on the out-of-date resolution can
// have the effect of getting us stuck with the stale resolution.
// One might think that if the last ResolutionChangeOrigin was apz then the
// pres shell resolutions should match but
// that is not the case. We can get multiple repaint requests that has the
// same pres shell resolution (because apz didn't receive a content layers
// update inbetween) if the first has async zoom we apply that and chance
// the content pres shell resolution and thus when handling the second
// repaint request the pres shell resolution won't match. So that's why we
// also check if the last resolution change origin was apz (aka 'us').
if (!FuzzyEqualsMultiplicative(presShellResolution,
aRequest.GetPresShellResolution()) &&
presShell->GetLastResolutionChangeOrigin() !=
ResolutionChangeOrigin::Apz) {
// The pres shell resolution is updated by the the async zoom since the
// last paint.
// We want to calculate the new presshell resolution as
// |aRequest.GetPresShellResolution() * aRequest.GetAsyncZoom()| but that
// calculation can lead to small inaccuracies due to limited floating point
// precision. Specifically,
// clang-format off
// asyncZoom = zoom / layerPixelsPerCSSPixel
// = zoom / (devPixelsPerCSSPixel * cumulativeResolution)
// clang-format on
// Since this is a root frame we generally do not allow css transforms to
// scale it, so it is very likely that cumulativeResolution ==
// presShellResoluion. So
// clang-format off
// newPresShellResoluion = presShellResoluion * asyncZoom
// = presShellResoluion * zoom / (devPixelsPerCSSPixel * presShellResoluion)
// = zoom / devPixelsPerCSSPixel
// clang-format on
// However, we want to keep the calculation general and so we do not assume
// presShellResoluion == cumulativeResolution, but rather factor those
// values out so they cancel and the floating point division has a very high
// probability of being exactly 1.
presShellResolution =
(aRequest.GetPresShellResolution() /
aRequest.GetCumulativeResolution().scale) *
(aRequest.GetZoom() / aRequest.GetDevPixelsPerCSSPixel()).scale;
// Changing the resolution will trigger a reflow which will cause the
// main-thread scroll position to be realigned in layer pixels. This
// (subpixel) scroll mutation can trigger a scroll update to APZ which
// is undesirable. Instead of having that happen as part of the post-reflow
// code, we force it to happen here with ScrollOrigin::Apz so that it
// doesn't trigger a scroll update to APZ.
ScrollContainerFrame* sf =
CSSPoint currentScrollPosition =
ScrollSnapTargetIds snapTargetIds = aRequest.GetLastSnapTargetIds();
// Do this as late as possible since scrolling can flush layout. It also
// adjusts the display port margins, so do it before we set those.
DisplayPortMargins displayPortMargins = ScrollFrame(content, aRequest);
SetDisplayPortMargins(presShell, content, displayPortMargins,
SetPaintRequestTime(content, aRequest.GetPaintRequestTime());
void APZCCallbackHelper::UpdateSubFrame(const RepaintRequest& aRequest) {
if (aRequest.GetScrollId() == ScrollableLayerGuid::NULL_SCROLL_ID) {
RefPtr<nsIContent> content =
if (!content) {
// We don't currently support zooming for subframes, so nothing extra
// needs to be done beyond the tasks common to this and UpdateRootFrame.
DisplayPortMargins displayPortMargins = ScrollFrame(content, aRequest);
if (RefPtr<PresShell> presShell = GetPresShell(content)) {
SetDisplayPortMargins(presShell, content, displayPortMargins,
SetPaintRequestTime(content, aRequest.GetPaintRequestTime());
bool APZCCallbackHelper::GetOrCreateScrollIdentifiers(
nsIContent* aContent, uint32_t* aPresShellIdOut,
ScrollableLayerGuid::ViewID* aViewIdOut) {
if (!aContent) {
return false;
*aViewIdOut = nsLayoutUtils::FindOrCreateIDFor(aContent);
if (PresShell* presShell = GetPresShell(aContent)) {
*aPresShellIdOut = presShell->GetPresShellId();
return true;
return false;
void APZCCallbackHelper::InitializeRootDisplayport(PresShell* aPresShell) {
// Create a view-id and set a zero-margin displayport for the root element
// of the root document in the chrome process. This ensures that the scroll
// frame for this element gets an APZC, which in turn ensures that all content
// in the chrome processes is covered by an APZC.
// The displayport is zero-margin because this element is generally not
// actually scrollable (if it is, APZC will set proper margins when it's
// scrolled).
if (!aPresShell) {
nsIContent* content = aPresShell->GetDocument()->GetDocumentElement();
if (!content) {
uint32_t presShellId;
ScrollableLayerGuid::ViewID viewId;
if (APZCCallbackHelper::GetOrCreateScrollIdentifiers(content, &presShellId,
&viewId)) {
sDisplayportLog, LogLevel::Debug,
("Initializing root displayport on scrollId=%" PRIu64 "\n", viewId));
Maybe<nsRect> baseRect =
if (baseRect) {
DisplayPortUtils::SetDisplayPortBaseIfNotSet(content, *baseRect);
content, aPresShell, DisplayPortMargins::Empty(content),
DisplayPortUtils::ClearMinimalDisplayPortProperty::Yes, 0);
nsPresContext* APZCCallbackHelper::GetPresContextForContent(
nsIContent* aContent) {
dom::Document* doc = aContent->GetComposedDoc();
if (!doc) {
return nullptr;
PresShell* presShell = doc->GetPresShell();
if (!presShell) {
return nullptr;
return presShell->GetPresContext();
PresShell* APZCCallbackHelper::GetRootContentDocumentPresShellForContent(
nsIContent* aContent) {
nsPresContext* context = GetPresContextForContent(aContent);
if (!context) {
return nullptr;
context = context->GetInProcessRootContentDocumentPresContext();
if (!context) {
return nullptr;
return context->PresShell();
nsEventStatus APZCCallbackHelper::DispatchWidgetEvent(WidgetGUIEvent& aEvent) {
nsEventStatus status = nsEventStatus_eConsumeNoDefault;
if (aEvent.mWidget) {
aEvent.mWidget->DispatchEvent(&aEvent, status);
return status;
nsEventStatus APZCCallbackHelper::DispatchSynthesizedMouseEvent(
EventMessage aMsg, const LayoutDevicePoint& aRefPoint, Modifiers aModifiers,
int32_t aClickCount, PrecedingPointerDown aPrecedingPointerDownState,
nsIWidget* aWidget) {
MOZ_ASSERT(aMsg == eMouseMove || aMsg == eMouseDown || aMsg == eMouseUp ||
aMsg == eMouseLongTap);
WidgetMouseEvent event(true, aMsg, aWidget, WidgetMouseEvent::eReal);
event.mRefPoint = LayoutDeviceIntPoint::Truncate(aRefPoint.x, aRefPoint.y);
event.mButton = MouseButton::ePrimary;
event.mButtons = aMsg == eMouseDown ? MouseButtonsFlag::ePrimaryFlag
: MouseButtonsFlag::eNoButtons;
event.mInputSource = dom::MouseEvent_Binding::MOZ_SOURCE_TOUCH;
if (aMsg == eMouseLongTap) {
event.mFlags.mOnlyChromeDispatch = true;
// If the preceding `pointerdown` was canceled by content, we should not
// dispatch the compatibility mouse events into the content, but they are
// required to dispatch `click`, `dblclick` and `auxclick` events by
// EventStateManager. Therefore, we need to dispatch them only to chrome.
else if (aPrecedingPointerDownState ==
PrecedingPointerDown::ConsumedByContent) {
event.mFlags.mOnlyChromeDispatch = true;
if (aMsg != eMouseMove) {
event.mClickCount = aClickCount;
event.mModifiers = aModifiers;
// Real touch events will generate corresponding pointer events. We set
// convertToPointer to false to prevent the synthesized mouse events generate
// pointer events again.
event.convertToPointer = false;
return DispatchWidgetEvent(event);
PreventDefaultResult APZCCallbackHelper::DispatchMouseEvent(
PresShell* aPresShell, const nsString& aType, const CSSPoint& aPoint,
int32_t aButton, int32_t aClickCount, int32_t aModifiers,
unsigned short aInputSourceArg, uint32_t aPointerId) {
NS_ENSURE_TRUE(aPresShell, PreventDefaultResult::ByContent);
PreventDefaultResult preventDefaultResult;
aPresShell, aType, aPoint.x, aPoint.y, aButton,
nsIDOMWindowUtils::MOUSE_BUTTONS_NOT_SPECIFIED, aClickCount, aModifiers,
/* aIgnoreRootScrollFrame = */ false, 0, aInputSourceArg, aPointerId,
false, &preventDefaultResult, false,
/* aIsWidgetEventSynthesized = */ false);
return preventDefaultResult;
void APZCCallbackHelper::FireSingleTapEvent(
const LayoutDevicePoint& aPoint, Modifiers aModifiers, int32_t aClickCount,
PrecedingPointerDown aPrecedingPointerDownState, nsIWidget* aWidget) {
if (aWidget->Destroyed()) {
APZCCH_LOG("Dispatching single-tap component events to %s\n",
DispatchSynthesizedMouseEvent(eMouseMove, aPoint, aModifiers, aClickCount,
aPrecedingPointerDownState, aWidget);
DispatchSynthesizedMouseEvent(eMouseDown, aPoint, aModifiers, aClickCount,
aPrecedingPointerDownState, aWidget);
DispatchSynthesizedMouseEvent(eMouseUp, aPoint, aModifiers, aClickCount,
aPrecedingPointerDownState, aWidget);
static dom::Element* GetDisplayportElementFor(
ScrollContainerFrame* aScrollContainerFrame) {
if (!aScrollContainerFrame) {
return nullptr;
nsIFrame* scrolledFrame = aScrollContainerFrame->GetScrolledFrame();
if (!scrolledFrame) {
return nullptr;
// |scrolledFrame| should at this point be the root content frame of the
// nearest ancestor scrollable frame. The element corresponding to this
// frame should be the one with the displayport set on it, so find that
// element and return it.
nsIContent* content = scrolledFrame->GetContent();
MOZ_ASSERT(content->IsElement()); // roc says this must be true
return content->AsElement();
static dom::Element* GetRootDocumentElementFor(nsIWidget* aWidget) {
// This returns the root element that ChromeProcessController sets the
// displayport on during initialization.
if (nsView* view = nsView::GetViewFor(aWidget)) {
if (PresShell* presShell = view->GetPresShell()) {
return presShell->GetDocument()->GetDocumentElement();
return nullptr;
namespace {
using FrameForPointOption = nsLayoutUtils::FrameForPointOption;
// Determine the scrollable target frame for the given point and add it to
// the target list. If the frame doesn't have a displayport, set one.
// Return whether or not the frame had a displayport that has already been
// painted (in this case, the caller can send the SetTargetAPZC notification
// right away, rather than waiting for a transaction to propagate the
// displayport to APZ first).
static bool PrepareForSetTargetAPZCNotification(
nsIWidget* aWidget, const LayersId& aLayersId, nsIFrame* aRootFrame,
const LayoutDeviceIntPoint& aRefPoint,
nsTArray<ScrollableLayerGuid>* aTargets) {
ScrollableLayerGuid guid(aLayersId, 0, ScrollableLayerGuid::NULL_SCROLL_ID);
RelativeTo relativeTo{aRootFrame, ViewportType::Visual};
nsPoint point = nsLayoutUtils::GetEventCoordinatesRelativeTo(
aWidget, aRefPoint, relativeTo);
nsIFrame* target = nsLayoutUtils::GetFrameForPoint(relativeTo, point);
ScrollContainerFrame* scrollAncestor =
target ? nsLayoutUtils::GetAsyncScrollableAncestorFrame(target)
: aRootFrame->PresShell()->GetRootScrollContainerFrame();
// Assuming that if there's no scrollAncestor, there's already a displayPort.
nsCOMPtr<dom::Element> dpElement =
scrollAncestor ? GetDisplayportElementFor(scrollAncestor)
: GetRootDocumentElementFor(aWidget);
if (MOZ_LOG_TEST(sApzHlpLog, LogLevel::Debug)) {
nsAutoString dpElementDesc;
if (dpElement) {
APZCCH_LOG("For event at %s found scrollable element %p (%s)\n",
ToString(aRefPoint).c_str(), dpElement.get(),
bool guidIsValid = APZCCallbackHelper::GetOrCreateScrollIdentifiers(
dpElement, &(guid.mPresShellId), &(guid.mScrollId));
if (!guidIsValid) {
return false;
if (DisplayPortUtils::HasNonMinimalNonZeroDisplayPort(dpElement)) {
// If the element has a displayport but it hasn't been painted yet,
// we want the caller to wait for the paint to happen, but we don't
// need to set the displayport here since it's already been set.
return !DisplayPortUtils::HasPaintedDisplayPort(dpElement);
if (!scrollAncestor) {
// This can happen if the document element gets swapped out after
// ChromeProcessController runs InitializeRootDisplayport. In this case
// let's try to set a displayport again and bail out on this operation.
APZCCH_LOG("Widget %p's document element %p didn't have a displayport\n",
aWidget, dpElement.get());
return false;
APZCCH_LOG("%p didn't have a displayport, so setting one...\n",
MOZ_LOG(sDisplayportLog, LogLevel::Debug,
("Activating displayport on scrollId=%" PRIu64 " for SetTargetAPZC\n",
bool activated = DisplayPortUtils::CalculateAndSetDisplayPortMargins(
scrollAncestor, DisplayPortUtils::RepaintMode::Repaint);
if (!activated) {
return false;
return !DisplayPortUtils::HasPaintedDisplayPort(dpElement);
static void SendLayersDependentApzcTargetConfirmation(
nsIWidget* aWidget, uint64_t aInputBlockId,
nsTArray<ScrollableLayerGuid>&& aTargets) {
WindowRenderer* renderer = aWidget->GetWindowRenderer();
if (!renderer) {
if (WebRenderLayerManager* wrlm = renderer->AsWebRender()) {
if (WebRenderBridgeChild* wrbc = wrlm->WrBridge()) {
wrbc->SendSetConfirmedTargetAPZC(aInputBlockId, aTargets);
} // namespace
nsIWidget* aWidget, nsPresContext* aPresContext,
const uint64_t& aInputBlockId, nsTArray<ScrollableLayerGuid>&& aTargets)
: ManagedPostRefreshObserver(aPresContext),
mTargets(std::move(aTargets)) {
MOZ_ASSERT(!mAction, "Setting Action twice");
mAction = [instance = MOZ_KnownLive(this)](bool aWasCanceled) {
return Unregister::Yes;
DisplayportSetListener::~DisplayportSetListener() = default;
void DisplayportSetListener::Register() {
void DisplayportSetListener::OnPostRefresh() {
APZCCH_LOG("Got refresh, sending target APZCs for input block %" PRIu64 "\n",
SendLayersDependentApzcTargetConfirmation(mWidget, mInputBlockId,
APZCCallbackHelper::SendSetTargetAPZCNotification(nsIWidget* aWidget,
dom::Document* aDocument,
const WidgetGUIEvent& aEvent,
const LayersId& aLayersId,
uint64_t aInputBlockId) {
if (!aWidget || !aDocument) {
return nullptr;
if (aInputBlockId == sLastTargetAPZCNotificationInputBlock) {
// We have already confirmed the target APZC for a previous event of this
// input block. If we activated a scroll frame for this input block,
// sending another target APZC confirmation would be harmful, as it might
// race the original confirmation (which needs to go through a layers
// transaction).
APZCCH_LOG("Not resending target APZC confirmation for input block %" PRIu64
return nullptr;
sLastTargetAPZCNotificationInputBlock = aInputBlockId;
if (PresShell* presShell = aDocument->GetPresShell()) {
if (nsIFrame* rootFrame = presShell->GetRootFrame()) {
bool waitForRefresh = false;
nsTArray<ScrollableLayerGuid> targets;
if (const WidgetTouchEvent* touchEvent = aEvent.AsTouchEvent()) {
for (size_t i = 0; i < touchEvent->mTouches.Length(); i++) {
waitForRefresh |= PrepareForSetTargetAPZCNotification(
aWidget, aLayersId, rootFrame, touchEvent->mTouches[i]->mRefPoint,
} else if (const WidgetWheelEvent* wheelEvent = aEvent.AsWheelEvent()) {
waitForRefresh = PrepareForSetTargetAPZCNotification(
aWidget, aLayersId, rootFrame, wheelEvent->mRefPoint, &targets);
} else if (const WidgetMouseEvent* mouseEvent = aEvent.AsMouseEvent()) {
waitForRefresh = PrepareForSetTargetAPZCNotification(
aWidget, aLayersId, rootFrame, mouseEvent->mRefPoint, &targets);
// TODO: Do other types of events need to be handled?
if (!targets.IsEmpty()) {
if (waitForRefresh) {
"At least one target got a new displayport, need to wait for "
return MakeAndAddRef<DisplayportSetListener>(
aWidget, presShell->GetPresContext(), aInputBlockId,
APZCCH_LOG("Sending target APZCs for input block %" PRIu64 "\n",
aWidget->SetConfirmedTargetAPZC(aInputBlockId, targets);
return nullptr;
void APZCCallbackHelper::NotifyMozMouseScrollEvent(
const ScrollableLayerGuid::ViewID& aScrollId, const nsString& aEvent) {
nsCOMPtr<nsIContent> targetContent = nsLayoutUtils::FindContentFor(aScrollId);
if (!targetContent) {
RefPtr<dom::Document> ownerDoc = targetContent->OwnerDoc();
if (!ownerDoc) {
nsContentUtils::DispatchEventOnlyToChrome(ownerDoc, targetContent, aEvent,
CanBubble::eYes, Cancelable::eYes);
void APZCCallbackHelper::NotifyFlushComplete(PresShell* aPresShell) {
// In some cases, flushing the APZ state to the main thread doesn't actually
// trigger a flush and repaint (this is an intentional optimization - the
// stuff visible to the user is still correct). However, reftests update their
// snapshot based on invalidation events that are emitted during paints,
// so we ensure that we kick off a paint when an APZ flush is done. Note that
// only chrome/testing code can trigger this behaviour.
if (aPresShell && aPresShell->GetRootFrame()) {
aPresShell->GetRootFrame()->SchedulePaint(nsIFrame::PAINT_DEFAULT, false);
nsCOMPtr<nsIObserverService> observerService =
observerService->NotifyObservers(nullptr, "apz-repaints-flushed", nullptr);
/* static */
bool APZCCallbackHelper::IsScrollInProgress(ScrollContainerFrame* aFrame) {
using AnimationState = ScrollContainerFrame::AnimationState;
return aFrame->ScrollAnimationState().contains(AnimationState::MainThread) ||
/* static */
void APZCCallbackHelper::NotifyAsyncScrollbarDragInitiated(
uint64_t aDragBlockId, const ScrollableLayerGuid::ViewID& aScrollId,
ScrollDirection aDirection) {
if (ScrollContainerFrame* scrollContainerFrame =
nsLayoutUtils::FindScrollContainerFrameFor(aScrollId)) {
scrollContainerFrame->AsyncScrollbarDragInitiated(aDragBlockId, aDirection);
/* static */
void APZCCallbackHelper::NotifyAsyncScrollbarDragRejected(
const ScrollableLayerGuid::ViewID& aScrollId) {
if (ScrollContainerFrame* scrollContainerFrame =
nsLayoutUtils::FindScrollContainerFrameFor(aScrollId)) {
/* static */
void APZCCallbackHelper::NotifyAsyncAutoscrollRejected(
const ScrollableLayerGuid::ViewID& aScrollId) {
nsCOMPtr<nsIObserverService> observerService =
nsAutoString data;
observerService->NotifyObservers(nullptr, "autoscroll-rejected-by-apz",
/* static */
void APZCCallbackHelper::CancelAutoscroll(
const ScrollableLayerGuid::ViewID& aScrollId) {
nsCOMPtr<nsIObserverService> observerService =
nsAutoString data;
observerService->NotifyObservers(nullptr, "apz:cancel-autoscroll",
/* static */
void APZCCallbackHelper::NotifyScaleGestureComplete(
const nsCOMPtr<nsIWidget>& aWidget, float aScale) {
if (nsView* view = nsView::GetViewFor(aWidget)) {
if (PresShell* presShell = view->GetPresShell()) {
dom::Document* doc = presShell->GetDocument();
if (nsPIDOMWindowInner* win = doc->GetInnerWindow()) {
dom::AutoJSAPI jsapi;
if (!jsapi.Init(win)) {
JSContext* cx =;
JS::Rooted<JS::Value> detail(cx, JS::Float32Value(aScale));
RefPtr<dom::CustomEvent> event =
NS_NewDOMCustomEvent(doc, nullptr, nullptr);
event->InitCustomEvent(cx, u"MozScaleGestureComplete"_ns,
/* CanBubble */ true,
/* Cancelable */ false, detail);
auto* dispatcher = new AsyncEventDispatcher(doc, event.forget(),
/* static */
void APZCCallbackHelper::NotifyPinchGesture(
PinchGestureInput::PinchGestureType aType,
const LayoutDevicePoint& aFocusPoint, LayoutDeviceCoord aSpanChange,
Modifiers aModifiers, const nsCOMPtr<nsIWidget>& aWidget) {
APZCCH_LOG("APZCCallbackHelper dispatching pinch gesture\n");
EventMessage msg;
switch (aType) {
case PinchGestureInput::PINCHGESTURE_START:
msg = eMagnifyGestureStart;
case PinchGestureInput::PINCHGESTURE_SCALE:
msg = eMagnifyGestureUpdate;
case PinchGestureInput::PINCHGESTURE_END:
msg = eMagnifyGesture;
WidgetSimpleGestureEvent event(true, msg, aWidget.get());
// XXX mDelta for the eMagnifyGesture event is supposed to be the
// cumulative magnification over the entire gesture (per docs in
// SimpleGestureEvent.webidl) but currently APZ just sends us a zero
// aSpanChange for that event, so the mDelta is wrong. Nothing relies
// on that currently, but we might want to fix it at some point.
event.mDelta = aSpanChange;
event.mModifiers = aModifiers;
event.mRefPoint = RoundedToInt(aFocusPoint);
} // namespace layers
} // namespace mozilla