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/* -*- 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 "HitTestInfoManager.h"
#include "HitTestInfo.h"
#include "nsDisplayList.h"
# define HITTEST_INFO_LOG(...) printf_stderr(__VA_ARGS__)
# define HITTEST_INFO_LOG(...)
namespace mozilla::layers {
using ViewID = ScrollableLayerGuid::ViewID;
* TODO(miko): This used to be a performance bottle-neck, but it does not show
* up in profiles anymore, see bugs 1424637 and 1424968.
* A better way of doing this would be to store current app units per dev pixel
* in wr::DisplayListBuilder, and update it whenever display items that separate
* presshell boundaries are encountered.
static int32_t GetAppUnitsFromDisplayItem(nsDisplayItem* aItem) {
nsIFrame* frame = aItem->Frame();
return frame->PresContext()->AppUnitsPerDevPixel();
static void CreateWebRenderCommands(wr::DisplayListBuilder& aBuilder,
nsDisplayItem* aItem, const nsRect& aArea,
const gfx::CompositorHitTestInfo& aFlags,
const ViewID& aViewId) {
const Maybe<SideBits> sideBits =
const LayoutDeviceRect devRect =
LayoutDeviceRect::FromAppUnits(aArea, GetAppUnitsFromDisplayItem(aItem));
const wr::LayoutRect rect = wr::ToLayoutRect(devRect);
aBuilder.PushHitTest(rect, rect, !aItem->BackfaceIsHidden(), aViewId, aFlags,
: mFlags(gfx::CompositorHitTestInvisibleToHit),
mSpaceAndClipChain(wr::InvalidScrollNodeWithChain()) {}
void HitTestInfoManager::Reset() {
mArea = nsRect();
mFlags = gfx::CompositorHitTestInvisibleToHit;
mViewId = ScrollableLayerGuid::NULL_SCROLL_ID;
mSpaceAndClipChain = wr::InvalidScrollNodeWithChain();
HITTEST_INFO_LOG("* HitTestInfoManager::Reset\n");
bool HitTestInfoManager::ProcessItem(
nsDisplayItem* aItem, wr::DisplayListBuilder& aBuilder,
nsDisplayListBuilder* aDisplayListBuilder) {
HITTEST_INFO_LOG("* HitTestInfoManager::ProcessItem(%d, %s, has=%d)\n",
getpid(), aItem->Frame()->ListTag().get(),
if (MOZ_UNLIKELY(aItem->GetType() == DisplayItemType::TYPE_REMOTE)) {
// Remote frames might contain hit-test-info items inside (but those
// aren't processed by this process of course), so we can't optimize out the
// next hit-test info item because it might be on top of the iframe.
if (!aItem->HasHitTestInfo()) {
return false;
const HitTestInfo& hitTestInfo = aItem->GetHitTestInfo();
const nsRect& area = hitTestInfo.Area();
const gfx::CompositorHitTestInfo& flags = hitTestInfo.Info();
if (flags == gfx::CompositorHitTestInvisibleToHit || area.IsEmpty()) {
return false;
const auto viewId =
hitTestInfo.GetViewId(aBuilder, aItem->GetActiveScrolledRoot());
const auto spaceAndClipChain = aBuilder.CurrentSpaceAndClipChain();
if (!Update(area, flags, viewId, spaceAndClipChain)) {
// The previous hit test information is still valid.
return false;
HITTEST_INFO_LOG("+ [%d, %d, %d, %d]: flags: 0x%x, viewId: %lu\n", area.x,
area.y, area.width, area.height, flags.serialize(), viewId);
CreateWebRenderCommands(aBuilder, aItem, area, flags, viewId);
return true;
* Updates the current hit testing information if necessary.
* Returns true if the hit testing information was changed.
bool HitTestInfoManager::Update(const nsRect& aArea,
const gfx::CompositorHitTestInfo& aFlags,
const ViewID& aViewId,
const wr::WrSpaceAndClipChain& aSpaceAndClip) {
if (mViewId == aViewId && mFlags == aFlags && mArea.Contains(aArea) &&
mSpaceAndClipChain == aSpaceAndClip) {
// The previous hit testing information can be reused.
HITTEST_INFO_LOG("s [%d, %d, %d, %d]: flags: 0x%x, viewId: %lu\n", aArea.x,
aArea.y, aArea.width, aArea.height, aFlags.serialize(),
return false;
mArea = aArea;
mFlags = aFlags;
mViewId = aViewId;
mSpaceAndClipChain = aSpaceAndClip;
return true;
} // namespace mozilla::layers