Adding upstream version 110.0.1.upstream/110.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 614 insertions, 0 deletions

diff --git a/layout/base/PositionedEventTargeting.cpp b/layout/base/PositionedEventTargeting.cpp
new file mode 100644
index 0000000000..533f3e4932
--- /dev/null
+++ b/layout/base/PositionedEventTargeting.cpp
@@ -0,0 +1,614 @@
+/* -*- 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 "PositionedEventTargeting.h"
+
+#include "mozilla/EventListenerManager.h"
+#include "mozilla/MouseEvents.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/StaticPrefs_ui.h"
+#include "mozilla/ToString.h"
+#include "mozilla/dom/MouseEventBinding.h"
+#include "nsContainerFrame.h"
+#include "nsFrameList.h"  // for DEBUG_FRAME_DUMP
+#include "nsHTMLParts.h"
+#include "nsLayoutUtils.h"
+#include "nsGkAtoms.h"
+#include "nsFontMetrics.h"
+#include "nsPrintfCString.h"
+#include "mozilla/dom/Element.h"
+#include "nsRegion.h"
+#include "nsDeviceContext.h"
+#include "nsIContentInlines.h"
+#include "nsIFrame.h"
+#include <algorithm>
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+// If debugging this code you may wish to enable this logging, via
+// the env var MOZ_LOG="event.retarget:4". For extra logging (getting
+// frame dumps, use MOZ_LOG="event.retarget:5".
+static mozilla::LazyLogModule sEvtTgtLog("event.retarget");
+#define PET_LOG(...) MOZ_LOG(sEvtTgtLog, LogLevel::Debug, (__VA_ARGS__))
+
+namespace mozilla {
+
+/*
+ * The basic goal of FindFrameTargetedByInputEvent() is to find a good
+ * target element that can respond to mouse events. Both mouse events and touch
+ * events are targeted at this element. Note that even for touch events, we
+ * check responsiveness to mouse events. We assume Web authors
+ * designing for touch events will take their own steps to account for
+ * inaccurate touch events.
+ *
+ * GetClickableAncestor() encapsulates the heuristic that determines whether an
+ * element is expected to respond to mouse events. An element is deemed
+ * "clickable" if it has registered listeners for "click", "mousedown" or
+ * "mouseup", or is on a whitelist of element tags (<a>, <button>, <input>,
+ * <select>, <textarea>, <label>), or has role="button", or is a link, or
+ * is a suitable XUL element.
+ * Any descendant (in the same document) of a clickable element is also
+ * deemed clickable since events will propagate to the clickable element from
+ * its descendant.
+ *
+ * If the element directly under the event position is clickable (or
+ * event radii are disabled), we always use that element. Otherwise we collect
+ * all frames intersecting a rectangle around the event position (taking CSS
+ * transforms into account) and choose the best candidate in GetClosest().
+ * Only GetClickableAncestor() candidates are considered; if none are found,
+ * then we revert to targeting the element under the event position.
+ * We ignore candidates outside the document subtree rooted by the
+ * document of the element directly under the event position. This ensures that
+ * event listeners in ancestor documents don't make it completely impossible
+ * to target a non-clickable element in a child document.
+ *
+ * When both a frame and its ancestor are in the candidate list, we ignore
+ * the ancestor. Otherwise a large ancestor element with a mouse event listener
+ * and some descendant elements that need to be individually targetable would
+ * disable intelligent targeting of those descendants within its bounds.
+ *
+ * GetClosest() computes the transformed axis-aligned bounds of each
+ * candidate frame, then computes the Manhattan distance from the event point
+ * to the bounds rect (which can be zero). The frame with the
+ * shortest distance is chosen. For visited links we multiply the distance
+ * by a specified constant weight; this can be used to make visited links
+ * more or less likely to be targeted than non-visited links.
+ */
+
+// Enum that determines which type of elements to count as targets in the
+// search. Clickable elements are generally ones that respond to click events,
+// like form inputs and links and things with click event listeners.
+// Touchable elements are a much narrower set of elements; ones with touchstart
+// and touchend listeners.
+enum class SearchType {
+  None,
+  Clickable,
+  Touchable,
+};
+
+struct EventRadiusPrefs {
+  bool mEnabled;            // other fields are valid iff this field is true
+  uint32_t mVisitedWeight;  // in percent, i.e. default is 100
+  uint32_t mRadiusTopmm;
+  uint32_t mRadiusRightmm;
+  uint32_t mRadiusBottommm;
+  uint32_t mRadiusLeftmm;
+  bool mTouchOnly;
+  bool mReposition;
+  SearchType mSearchType;
+
+  explicit EventRadiusPrefs(EventClassID aEventClassID) {
+    if (aEventClassID == eTouchEventClass) {
+      mEnabled = StaticPrefs::ui_touch_radius_enabled();
+      mVisitedWeight = StaticPrefs::ui_touch_radius_visitedWeight();
+      mRadiusTopmm = StaticPrefs::ui_touch_radius_topmm();
+      mRadiusRightmm = StaticPrefs::ui_touch_radius_rightmm();
+      mRadiusBottommm = StaticPrefs::ui_touch_radius_bottommm();
+      mRadiusLeftmm = StaticPrefs::ui_touch_radius_leftmm();
+      mTouchOnly = false;   // Always false, unlike mouse events.
+      mReposition = false;  // Always false, unlike mouse events.
+      mSearchType = SearchType::Touchable;
+
+    } else if (aEventClassID == eMouseEventClass) {
+      mEnabled = StaticPrefs::ui_mouse_radius_enabled();
+      mVisitedWeight = StaticPrefs::ui_mouse_radius_visitedWeight();
+      mRadiusTopmm = StaticPrefs::ui_mouse_radius_topmm();
+      mRadiusRightmm = StaticPrefs::ui_mouse_radius_rightmm();
+      mRadiusBottommm = StaticPrefs::ui_mouse_radius_bottommm();
+      mRadiusLeftmm = StaticPrefs::ui_mouse_radius_leftmm();
+      mTouchOnly = StaticPrefs::ui_mouse_radius_inputSource_touchOnly();
+      mReposition = StaticPrefs::ui_mouse_radius_reposition();
+      mSearchType = SearchType::Clickable;
+
+    } else {
+      mEnabled = false;
+      mVisitedWeight = 0;
+      mRadiusTopmm = 0;
+      mRadiusRightmm = 0;
+      mRadiusBottommm = 0;
+      mRadiusLeftmm = 0;
+      mTouchOnly = false;
+      mReposition = false;
+      mSearchType = SearchType::None;
+    }
+  }
+};
+
+static bool HasMouseListener(nsIContent* aContent) {
+  if (EventListenerManager* elm = aContent->GetExistingListenerManager()) {
+    return elm->HasListenersFor(nsGkAtoms::onclick) ||
+           elm->HasListenersFor(nsGkAtoms::onmousedown) ||
+           elm->HasListenersFor(nsGkAtoms::onmouseup);
+  }
+
+  return false;
+}
+
+static bool HasTouchListener(nsIContent* aContent) {
+  EventListenerManager* elm = aContent->GetExistingListenerManager();
+  if (!elm) {
+    return false;
+  }
+
+  // FIXME: Should this really use the pref rather than TouchEvent::PrefEnabled
+  // or such?
+  if (!StaticPrefs::dom_w3c_touch_events_enabled()) {
+    return false;
+  }
+
+  return elm->HasNonSystemGroupListenersFor(nsGkAtoms::ontouchstart) ||
+         elm->HasNonSystemGroupListenersFor(nsGkAtoms::ontouchend);
+}
+
+static bool HasPointerListener(nsIContent* aContent) {
+  EventListenerManager* elm = aContent->GetExistingListenerManager();
+  if (!elm) {
+    return false;
+  }
+
+  return elm->HasListenersFor(nsGkAtoms::onpointerdown) ||
+         elm->HasListenersFor(nsGkAtoms::onpointerup);
+}
+
+static bool IsDescendant(nsIFrame* aFrame, nsIContent* aAncestor,
+                         nsAutoString* aLabelTargetId) {
+  for (nsIContent* content = aFrame->GetContent(); content;
+       content = content->GetFlattenedTreeParent()) {
+    if (aLabelTargetId && content->IsHTMLElement(nsGkAtoms::label)) {
+      content->AsElement()->GetAttr(kNameSpaceID_None, nsGkAtoms::_for,
+                                    *aLabelTargetId);
+    }
+    if (content == aAncestor) {
+      return true;
+    }
+  }
+  return false;
+}
+
+static nsIContent* GetTouchableAncestor(nsIFrame* aFrame,
+                                        nsAtom* aStopAt = nullptr) {
+  // Input events propagate up the content tree so we'll follow the content
+  // ancestors to look for elements accepting the touch event.
+  for (nsIContent* content = aFrame->GetContent(); content;
+       content = content->GetFlattenedTreeParent()) {
+    if (aStopAt && content->IsHTMLElement(aStopAt)) {
+      break;
+    }
+    if (HasTouchListener(content)) {
+      return content;
+    }
+  }
+  return nullptr;
+}
+
+static nsIContent* GetClickableAncestor(
+    nsIFrame* aFrame, nsAtom* aStopAt = nullptr,
+    nsAutoString* aLabelTargetId = nullptr) {
+  // If the frame is `cursor:pointer` or inherits `cursor:pointer` from an
+  // ancestor, treat it as clickable. This is a heuristic to deal with pages
+  // where the click event listener is on the <body> or <html> element but it
+  // triggers an action on some specific element. We want the specific element
+  // to be considered clickable, and at least some pages that do this indicate
+  // the clickability by setting `cursor:pointer`, so we use that here.
+  // Note that descendants of `cursor:pointer` elements that override the
+  // inherited `pointer` to `auto` or any other value are NOT treated as
+  // clickable, because it seems like the content author is trying to express
+  // non-clickability on that sub-element.
+  // In the future depending on real-world cases it might make sense to expand
+  // this check to any non-auto cursor. Such a change would also pick up things
+  // like contenteditable or input fields, which can then be removed from the
+  // loop below, and would have better performance.
+  if (aFrame->StyleUI()->Cursor().keyword == StyleCursorKind::Pointer) {
+    return aFrame->GetContent();
+  }
+
+  // Input events propagate up the content tree so we'll follow the content
+  // ancestors to look for elements accepting the click.
+  for (nsIContent* content = aFrame->GetContent(); content;
+       content = content->GetFlattenedTreeParent()) {
+    if (aStopAt && content->IsHTMLElement(aStopAt)) {
+      break;
+    }
+    if (HasTouchListener(content) || HasMouseListener(content) ||
+        HasPointerListener(content)) {
+      return content;
+    }
+    if (content->IsAnyOfHTMLElements(nsGkAtoms::button, nsGkAtoms::input,
+                                     nsGkAtoms::select, nsGkAtoms::textarea)) {
+      return content;
+    }
+    if (content->IsHTMLElement(nsGkAtoms::label)) {
+      if (aLabelTargetId) {
+        content->AsElement()->GetAttr(kNameSpaceID_None, nsGkAtoms::_for,
+                                      *aLabelTargetId);
+      }
+      return content;
+    }
+
+    // Bug 921928: we don't have access to the content of remote iframe.
+    // So fluffing won't go there. We do an optimistic assumption here:
+    // that the content of the remote iframe needs to be a target.
+    if (content->IsHTMLElement(nsGkAtoms::iframe) &&
+        content->AsElement()->AttrValueIs(kNameSpaceID_None,
+                                          nsGkAtoms::mozbrowser,
+                                          nsGkAtoms::_true, eIgnoreCase) &&
+        content->AsElement()->AttrValueIs(kNameSpaceID_None, nsGkAtoms::remote,
+                                          nsGkAtoms::_true, eIgnoreCase)) {
+      return content;
+    }
+
+    // See nsCSSFrameConstructor::FindXULTagData. This code is not
+    // really intended to be used with XUL, though.
+    if (content->IsAnyOfXULElements(
+            nsGkAtoms::button, nsGkAtoms::checkbox, nsGkAtoms::radio,
+            nsGkAtoms::menu, nsGkAtoms::menuitem, nsGkAtoms::menulist,
+            nsGkAtoms::scrollbarbutton, nsGkAtoms::resizer)) {
+      return content;
+    }
+
+    static Element::AttrValuesArray clickableRoles[] = {
+        nsGkAtoms::button, nsGkAtoms::key, nullptr};
+    if (auto* element = Element::FromNode(*content)) {
+      if (element->IsLink()) {
+        return content;
+      }
+      if (element->FindAttrValueIn(kNameSpaceID_None, nsGkAtoms::role,
+                                   clickableRoles, eIgnoreCase) >= 0) {
+        return content;
+      }
+    }
+    if (content->IsEditable()) {
+      return content;
+    }
+  }
+  return nullptr;
+}
+
+static nscoord AppUnitsFromMM(RelativeTo aFrame, uint32_t aMM) {
+  nsPresContext* pc = aFrame.mFrame->PresContext();
+  float result = float(aMM) * (pc->DeviceContext()->AppUnitsPerPhysicalInch() /
+                               MM_PER_INCH_FLOAT);
+  if (aFrame.mViewportType == ViewportType::Layout) {
+    PresShell* presShell = pc->PresShell();
+    result = result / presShell->GetResolution();
+  }
+  return NSToCoordRound(result);
+}
+
+/**
+ * Clip aRect with the bounds of aFrame in the coordinate system of
+ * aRootFrame. aRootFrame is an ancestor of aFrame.
+ */
+static nsRect ClipToFrame(RelativeTo aRootFrame, const nsIFrame* aFrame,
+                          nsRect& aRect) {
+  nsRect bound = nsLayoutUtils::TransformFrameRectToAncestor(
+      aFrame, nsRect(nsPoint(0, 0), aFrame->GetSize()), aRootFrame);
+  nsRect result = bound.Intersect(aRect);
+  return result;
+}
+
+static nsRect GetTargetRect(RelativeTo aRootFrame,
+                            const nsPoint& aPointRelativeToRootFrame,
+                            const nsIFrame* aRestrictToDescendants,
+                            const EventRadiusPrefs& aPrefs, uint32_t aFlags) {
+  nsMargin m(AppUnitsFromMM(aRootFrame, aPrefs.mRadiusTopmm),
+             AppUnitsFromMM(aRootFrame, aPrefs.mRadiusRightmm),
+             AppUnitsFromMM(aRootFrame, aPrefs.mRadiusBottommm),
+             AppUnitsFromMM(aRootFrame, aPrefs.mRadiusLeftmm));
+  nsRect r(aPointRelativeToRootFrame, nsSize(0, 0));
+  r.Inflate(m);
+  if (!(aFlags & INPUT_IGNORE_ROOT_SCROLL_FRAME)) {
+    // Don't clip this rect to the root scroll frame if the flag to ignore the
+    // root scroll frame is set. Note that the GetClosest code will still
+    // enforce that the target found is a descendant of aRestrictToDescendants.
+    r = ClipToFrame(aRootFrame, aRestrictToDescendants, r);
+  }
+  return r;
+}
+
+static float ComputeDistanceFromRect(const nsPoint& aPoint,
+                                     const nsRect& aRect) {
+  nscoord dx =
+      std::max(0, std::max(aRect.x - aPoint.x, aPoint.x - aRect.XMost()));
+  nscoord dy =
+      std::max(0, std::max(aRect.y - aPoint.y, aPoint.y - aRect.YMost()));
+  return float(NS_hypot(dx, dy));
+}
+
+static float ComputeDistanceFromRegion(const nsPoint& aPoint,
+                                       const nsRegion& aRegion) {
+  MOZ_ASSERT(!aRegion.IsEmpty(),
+             "can't compute distance between point and empty region");
+  float minDist = -1;
+  for (auto iter = aRegion.RectIter(); !iter.Done(); iter.Next()) {
+    float dist = ComputeDistanceFromRect(aPoint, iter.Get());
+    if (dist < minDist || minDist < 0) {
+      minDist = dist;
+    }
+  }
+  return minDist;
+}
+
+// Subtract aRegion from aExposedRegion as long as that doesn't make the
+// exposed region get too complex or removes a big chunk of the exposed region.
+static void SubtractFromExposedRegion(nsRegion* aExposedRegion,
+                                      const nsRegion& aRegion) {
+  if (aRegion.IsEmpty()) {
+    return;
+  }
+
+  nsRegion tmp;
+  tmp.Sub(*aExposedRegion, aRegion);
+  // Don't let *aExposedRegion get too complex, but don't let it fluff out to
+  // its bounds either. Do let aExposedRegion get more complex if by doing so
+  // we reduce its area by at least half.
+  if (tmp.GetNumRects() <= 15 || tmp.Area() <= aExposedRegion->Area() / 2) {
+    *aExposedRegion = tmp;
+  }
+}
+
+static nsIFrame* GetClosest(RelativeTo aRoot,
+                            const nsPoint& aPointRelativeToRootFrame,
+                            const nsRect& aTargetRect,
+                            const EventRadiusPrefs& aPrefs,
+                            const nsIFrame* aRestrictToDescendants,
+                            nsIContent* aClickableAncestor,
+                            nsTArray<nsIFrame*>& aCandidates) {
+  nsIFrame* bestTarget = nullptr;
+  // Lower is better; distance is in appunits
+  float bestDistance = 1e6f;
+  nsRegion exposedRegion(aTargetRect);
+  for (uint32_t i = 0; i < aCandidates.Length(); ++i) {
+    nsIFrame* f = aCandidates[i];
+
+    bool preservesAxisAlignedRectangles = false;
+    nsRect borderBox = nsLayoutUtils::TransformFrameRectToAncestor(
+        f, nsRect(nsPoint(0, 0), f->GetSize()), aRoot,
+        &preservesAxisAlignedRectangles);
+    PET_LOG("Checking candidate %p with border box %s\n", f,
+            ToString(borderBox).c_str());
+    nsRegion region;
+    region.And(exposedRegion, borderBox);
+    if (region.IsEmpty()) {
+      PET_LOG("  candidate %p had empty hit region\n", f);
+      continue;
+    }
+
+    if (preservesAxisAlignedRectangles) {
+      // Subtract from the exposed region if we have a transform that won't make
+      // the bounds include a bunch of area that we don't actually cover.
+      SubtractFromExposedRegion(&exposedRegion, region);
+    }
+
+    nsAutoString labelTargetId;
+    if (aClickableAncestor &&
+        !IsDescendant(f, aClickableAncestor, &labelTargetId)) {
+      PET_LOG("  candidate %p is not a descendant of required ancestor\n", f);
+      continue;
+    }
+
+    if (aPrefs.mSearchType == SearchType::Clickable) {
+      nsIContent* clickableContent =
+          GetClickableAncestor(f, nsGkAtoms::body, &labelTargetId);
+      if (!aClickableAncestor && !clickableContent) {
+        PET_LOG("  candidate %p was not clickable\n", f);
+        continue;
+      }
+    } else if (aPrefs.mSearchType == SearchType::Touchable) {
+      nsIContent* touchableContent = GetTouchableAncestor(f, nsGkAtoms::body);
+      if (!touchableContent) {
+        PET_LOG("  candidate %p was not touchable\n", f);
+        continue;
+      }
+    }
+
+    // If our current closest frame is a descendant of 'f', skip 'f' (prefer
+    // the nested frame).
+    if (bestTarget && nsLayoutUtils::IsProperAncestorFrameCrossDoc(
+                          f, bestTarget, aRoot.mFrame)) {
+      PET_LOG("  candidate %p was ancestor for bestTarget %p\n", f, bestTarget);
+      continue;
+    }
+    if (!aClickableAncestor && !nsLayoutUtils::IsAncestorFrameCrossDoc(
+                                   aRestrictToDescendants, f, aRoot.mFrame)) {
+      PET_LOG("  candidate %p was not descendant of restrictroot %p\n", f,
+              aRestrictToDescendants);
+      continue;
+    }
+
+    // distance is in appunits
+    float distance =
+        ComputeDistanceFromRegion(aPointRelativeToRootFrame, region);
+    nsIContent* content = f->GetContent();
+    if (content && content->IsElement() &&
+        content->AsElement()->State().HasState(
+            ElementState(ElementState::VISITED))) {
+      distance *= aPrefs.mVisitedWeight / 100.0f;
+    }
+    if (distance < bestDistance) {
+      PET_LOG("  candidate %p is the new best\n", f);
+      bestDistance = distance;
+      bestTarget = f;
+    }
+  }
+  return bestTarget;
+}
+
+// Walk from aTarget up to aRoot, and return the first frame found with an
+// explicit z-index set on it. If no such frame is found, aRoot is returned.
+static const nsIFrame* FindZIndexAncestor(const nsIFrame* aTarget,
+                                          const nsIFrame* aRoot) {
+  const nsIFrame* candidate = aTarget;
+  while (candidate && candidate != aRoot) {
+    if (candidate->ZIndex().valueOr(0) > 0) {
+      PET_LOG("Restricting search to z-index root %p\n", candidate);
+      return candidate;
+    }
+    candidate = candidate->GetParent();
+  }
+  return aRoot;
+}
+
+nsIFrame* FindFrameTargetedByInputEvent(
+    WidgetGUIEvent* aEvent, RelativeTo aRootFrame,
+    const nsPoint& aPointRelativeToRootFrame, uint32_t aFlags) {
+  using FrameForPointOption = nsLayoutUtils::FrameForPointOption;
+  EnumSet<FrameForPointOption> options;
+  if (aFlags & INPUT_IGNORE_ROOT_SCROLL_FRAME) {
+    options += FrameForPointOption::IgnoreRootScrollFrame;
+  }
+  nsIFrame* target = nsLayoutUtils::GetFrameForPoint(
+      aRootFrame, aPointRelativeToRootFrame, options);
+  PET_LOG(
+      "Found initial target %p for event class %s message %s point %s "
+      "relative to root frame %s\n",
+      target, ToChar(aEvent->mClass), ToChar(aEvent->mMessage),
+      ToString(aPointRelativeToRootFrame).c_str(),
+      ToString(aRootFrame).c_str());
+
+  EventRadiusPrefs prefs(aEvent->mClass);
+  if (!prefs.mEnabled || EventRetargetSuppression::IsActive()) {
+    PET_LOG("Retargeting disabled\n");
+    return target;
+  }
+
+  // Do not modify targeting for actual mouse hardware; only for mouse
+  // events generated by touch-screen hardware.
+  if (aEvent->mClass == eMouseEventClass && prefs.mTouchOnly &&
+      aEvent->AsMouseEvent()->mInputSource !=
+          MouseEvent_Binding::MOZ_SOURCE_TOUCH) {
+    PET_LOG("Mouse input event is not from a touch source\n");
+    return target;
+  }
+
+  // If the exact target is non-null, only consider candidate targets in the
+  // same document as the exact target. Otherwise, if an ancestor document has
+  // a mouse event handler for example, targets that are !GetClickableAncestor
+  // can never be targeted --- something nsSubDocumentFrame in an ancestor
+  // document would be targeted instead.
+  const nsIFrame* restrictToDescendants = [&]() -> const nsIFrame* {
+    if (target && target->PresContext() != aRootFrame.mFrame->PresContext()) {
+      return target->PresShell()->GetRootFrame();
+    }
+    return aRootFrame.mFrame;
+  }();
+
+  // If the target element inside an element with a z-index, restrict the
+  // search to other elements inside that z-index. This is a heuristic
+  // intended to help with a class of scenarios involving web modals or
+  // web popup type things. In particular it helps alleviate bug 1666792.
+  restrictToDescendants = FindZIndexAncestor(target, restrictToDescendants);
+
+  nsRect targetRect = GetTargetRect(aRootFrame, aPointRelativeToRootFrame,
+                                    restrictToDescendants, prefs, aFlags);
+  PET_LOG("Expanded point to target rect %s\n", ToString(targetRect).c_str());
+  AutoTArray<nsIFrame*, 8> candidates;
+  nsresult rv = nsLayoutUtils::GetFramesForArea(aRootFrame, targetRect,
+                                                candidates, options);
+  if (NS_FAILED(rv)) {
+    return target;
+  }
+
+  nsIContent* clickableAncestor = nullptr;
+  if (target) {
+    clickableAncestor = GetClickableAncestor(target, nsGkAtoms::body);
+    if (clickableAncestor) {
+      PET_LOG("Target %p is clickable\n", target);
+      // If the target that was directly hit has a clickable ancestor, that
+      // means it too is clickable. And since it is the same as or a
+      // descendant of clickableAncestor, it should become the root for the
+      // GetClosest search.
+      clickableAncestor = target->GetContent();
+    }
+  }
+
+  nsIFrame* closest =
+      GetClosest(aRootFrame, aPointRelativeToRootFrame, targetRect, prefs,
+                 restrictToDescendants, clickableAncestor, candidates);
+  if (closest) {
+    target = closest;
+  }
+
+  PET_LOG("Final target is %p\n", target);
+
+#ifdef DEBUG_FRAME_DUMP
+  // At verbose logging level, dump the frame tree to help with debugging.
+  // Note that dumping the frame tree at the top of the function may flood
+  // logcat on Android devices and cause the PET_LOGs to get dropped.
+  if (MOZ_LOG_TEST(sEvtTgtLog, LogLevel::Verbose)) {
+    if (target) {
+      target->DumpFrameTree();
+    } else {
+      aRootFrame.mFrame->DumpFrameTree();
+    }
+  }
+#endif
+
+  if (!target || !prefs.mReposition) {
+    // No repositioning required for this event
+    return target;
+  }
+
+  // Take the point relative to the root frame, make it relative to the target,
+  // clamp it to the bounds, and then make it relative to the root frame again.
+  nsPoint point = aPointRelativeToRootFrame;
+  if (nsLayoutUtils::TRANSFORM_SUCCEEDED !=
+      nsLayoutUtils::TransformPoint(aRootFrame, RelativeTo{target}, point)) {
+    return target;
+  }
+  point = target->GetRectRelativeToSelf().ClampPoint(point);
+  if (nsLayoutUtils::TRANSFORM_SUCCEEDED !=
+      nsLayoutUtils::TransformPoint(RelativeTo{target}, aRootFrame, point)) {
+    return target;
+  }
+  // Now we basically undo the operations in GetEventCoordinatesRelativeTo, to
+  // get back the (now-clamped) coordinates in the event's widget's space.
+  nsView* view = aRootFrame.mFrame->GetView();
+  if (!view) {
+    return target;
+  }
+  LayoutDeviceIntPoint widgetPoint = nsLayoutUtils::TranslateViewToWidget(
+      aRootFrame.mFrame->PresContext(), view, point, aRootFrame.mViewportType,
+      aEvent->mWidget);
+  if (widgetPoint.x != NS_UNCONSTRAINEDSIZE) {
+    // If that succeeded, we update the point in the event
+    aEvent->mRefPoint = widgetPoint;
+  }
+  return target;
+}
+
+uint32_t EventRetargetSuppression::sSuppressionCount = 0;
+
+EventRetargetSuppression::EventRetargetSuppression() { sSuppressionCount++; }
+
+EventRetargetSuppression::~EventRetargetSuppression() { sSuppressionCount--; }
+
+bool EventRetargetSuppression::IsActive() { return sSuppressionCount > 0; }
+
+}  // namespace mozilla