Bug 1760368 - A fixed element hit in the gutter should not be absorbed. r=botond

When a hit test result hits a fixed element that extends over the gutter, do not
absorb the event.

Depends on D147564

Differential Revision: https://phabricator.services.mozilla.com/D148077

gfx/layers/apz/src/APZCTreeManager.cpp

@@ -1889,8 +1889,9 @@ APZEventResult APZCTreeManager::InputHandlingState::Finish(
     mEvent.mLayersId = mHit.mLayersId;
   }
 
-  // If the event is over an overscroll gutter, do not dispatch it to Gecko.
-  if (mHit.mHitOverscrollGutter) {
+  // Absorb events that are in targetted at a position in the gutter,
+  // unless they are fixed position elements.
+  if (mHit.mHitOverscrollGutter && mHit.mFixedPosSides == SideBits::eNone) {
     mResult.SetStatusAsConsumeNoDefault();
   }
 

gfx/layers/apz/src/AsyncPanZoomController.h

@@ -1698,8 +1698,8 @@ class AsyncPanZoomController {
   // its composition bounds.
   bool Contains(const ScreenIntPoint& aPoint) const;
 
-  bool IsInOverscrollGutter(const ScreenPoint& aPoint) const;
-  bool IsInOverscrollGutter(const ParentLayerPoint& aPoint) const;
+  bool IsInOverscrollGutter(const ScreenPoint& aHitTestPoint) const;
+  bool IsInOverscrollGutter(const ParentLayerPoint& aHitTestPoint) const;
 
   bool IsOverscrolled() const;
 

gfx/layers/apz/test/mochitest/helper_hittest_overscroll.html

@@ -126,31 +126,42 @@ async function test() {
   // on both the browser chrome window and the content window.
   // This makes sure we catch the case where the overscroll transform causes
   // the event to incorrectly target the browser chrome.
-  startListeningForClickEventsInChrome();
-  let contentReceivedClick = false;
-  let contentListener = function(e) {
-    contentReceivedClick = true;
-  };
-  document.addEventListener("click", contentListener);
-  await synthesizeNativeMouseEventWithAPZ({
-    type: "click",
-    target: window,
-    offsetX: 100,
-    offsetY: 4
-  });
-  // Wait 10 frames for the event to maybe arrive, and if it
-  // hasn't, assume it won't.
-  for (let i = 0; i < 10; i++) {
-    await promiseFrame();
+
+  //// Util function to perform mouse events in the gutter. Used to ensure these
+  //// events are not dispatched to the content.
+  async function clickInGutter(xOffset, yOffset) {
+    startListeningForClickEventsInChrome();
+    let contentReceivedClick = false;
+    let contentListener = function(e) {
+      info("event clientX = " + e.clientX);
+      info("event clientY = " + e.clientY);
+      info("event target id: " + e.target.id);
+      contentReceivedClick = true;
+    };
+    document.addEventListener("click", contentListener);
+    await synthesizeNativeMouseEventWithAPZ({
+      type: "click",
+      target: window,
+      offsetX: xOffset,
+      offsetY: yOffset,
+    });
+    // Wait 10 frames for the event to maybe arrive, and if it
+    // hasn't, assume it won't.
+    for (let i = 0; i < 10; i++) {
+      await promiseFrame();
+    }
+    info("Finished waiting around for click event");
+    let chromeReceivedClick = await didChromeReceiveClick();
+    ok(!chromeReceivedClick,
+       "Gecko received click event in browser chrome when it shouldn't have");
+    ok(!contentReceivedClick,
+       "Gecko received click event targeting web content when it shouldn't have");
+    stopListeningForClickEventsInChrome();
+    document.removeEventListener("click", contentListener);
   }
-  info("Finished waiting around for click event");
-  let chromeReceivedClick = await didChromeReceiveClick();
-  ok(!chromeReceivedClick,
-     "Gecko received click event in browser chrome when it shouldn't have");
-  ok(!contentReceivedClick,
-     "Gecko received click event targeting web content when it shouldn't have");
-  stopListeningForClickEventsInChrome();
-  document.removeEventListener("click", contentListener);
+
+  // Perform the test
+  await clickInGutter(100, 4);
 
   // Finally, while still overscrolled, perform a click not in the gutter.
   // This event should successfully go through to the web content, and
@@ -193,6 +204,10 @@ async function test() {
     await clickFixedPromise;
   }
 
+  // This hit is technically in the gutter created by the overscroll, but we
+  // should still dispatch to gecko due to the fixed element extending into
+  // the gutter.
+  await clickFixed(4, fixedtarget, false);
   // Perform various mouse events to ensure the fixed element has not moved
   await clickFixed(10, fixedtarget, false);
   await clickFixed(14, fixedtargetbutton, false);
@@ -222,6 +237,11 @@ async function test() {
     offsetY: 25,
   });
   await clickFixedPromise;
+
+  // Click above the fixed element, but in the gutter.
+  await clickInGutter(302, 1);
+  // Click left of the the fixed element, but in the gutter.
+  await clickInGutter(298, 4);
 }
 
 waitUntilApzStable()