VSc: deactivate hover effects on scrolling

For #133
and philc/vimium#3273

content/scroller.ts

@@ -37,15 +37,16 @@ var VSc = {
 _animate (e: SafeElement | null, d: ScrollByY, a: number): void {
   let amount = 0, calibration = 1.0, di: ScrollByY = 0, duration = 0, element: SafeElement | null = null, //
   sign = 0, timestamp = 0, totalDelta = 0.0, totalElapsed = 0.0, //
-  running = 0 as number, next = requestAnimationFrame, timer = TimerID.None;
-  function animate(newTimestamp: number): void {
+  running = 0 as number, next = requestAnimationFrame, timer = TimerID.None,
+  top: SafeElement | null = null,
+  animate = (newTimestamp: number): void => {
+    if (!VSc) { toggleStyles(0); return; }
     const _this = VSc,
     // although timestamp is mono, Firefox adds too many limits to its precision
     elapsed = !timestamp ? (newTimestamp = performance.now(), ScrollerNS.Consts.firstTick)
               : newTimestamp > timestamp ? newTimestamp - timestamp
               : (newTimestamp += ScrollerNS.Consts.tickForUnexpectedTime, ScrollerNS.Consts.tickForUnexpectedTime),
     continuous = _this.keyIsDown_ > 0;
-    if (!_this) { return; }
     timestamp = newTimestamp;
     totalElapsed += elapsed;
     if (amount < ScrollerNS.Consts.AmountLimitToScrollAndWaitRepeatedKeys
@@ -80,15 +81,21 @@ _animate (e: SafeElement | null, d: ScrollByY, a: number): void {
         (notEl ? document : element as NonNullable<typeof element>).dispatchEvent(
             new Event("scrollend", {cancelable: false, bubbles: notEl}));
       }
+      toggleStyles(0);
       _this._checkCurrent(element);
       element = null;
       running = 0;
     }
-  }
-  function startAnimate(): void {
+  },
+  startAnimate = (): void => {
     timer = TimerID.None;
     running = running || next(animate);
-  }
+  },
+  toggleStyles = (scrolling: BOOL): void => {
+    const el = (scrolling ? top = VDom.SafeEl_(VDom.docEl_unsafe_()) : top
+        ) as TypeToAssert<Element, HTMLElement | SVGElement, "style"> | null;
+    el && el.style ? el.style.pointerEvents = scrolling ? "none" : "" : 0;
+  };
   this._animate = function (this: typeof VSc, newEl, newDi, newAmount): void {
     const math = Math, max = math.max;
     amount = max(1, math.abs(newAmount)); calibration = 1.0; di = newDi;
@@ -105,6 +112,7 @@ _animate (e: SafeElement | null, d: ScrollByY, a: number): void {
     this.minDelay_ = (((keyboard[0] + max(keyboard[1], ScrollerNS.Consts.DelayMinDelta)
           + ScrollerNS.Consts.DelayTolerance) / ScrollerNS.Consts.DelayUnitMs) | 0)
       * ScrollerNS.Consts.DelayUnitMs;
+    toggleStyles(1);
     startAnimate();
   };
   this._animate(e, d, a);

types/compatibility.d.ts

@@ -12,6 +12,7 @@ declare const enum BrowserVer {
   MinShadowDOMV0 = 31, // the real version is <= C31; it's prefixed
   // mouseEvent.buttons is since C43 but a `buttons` property does no harm on Chrome <= 42
   MinUsable$MouseEvent$$constructor = 31, // the real version is <= C31
+  MinEnsured$onwheel = 31, // even if LEGACY
   MinSupported = 32,
   MinEnsuredES6Promise = 32, // even if LEGACY
   // the 5 below are correct even if EXPERIMENTAL or LEGACY
@@ -117,6 +118,8 @@ declare const enum BrowserVer {
   // even if LEGACY
   MinEnsuredES6MethodFunction = 45, // e.g.: `a = { b() {} }`
   MinMuted = 45,
+  // https://www.chromestatus.com/features/5697181675683840
+  MinNoMousePositionUpdatesWhenScrolling = 45, // replaced by MinRuntimeFlag$UpdateHoverAtBeginFrame
   MinMutedInfo = 46,
   // even if EXPERIMENTAL or LEGACY
   MinAutoDecodeJSURL = 46,
@@ -435,6 +438,8 @@ declare const enum BrowserVer {
   // https://chromium.googlesource.com/chromium/src/+/5e84b7a819637ed4dd8f9c4d11288127663c8267
   MinBlockAutoFocusingInCrossOriginFrame = 75,
   MinMediaQuery$PrefersColorScheme = 76,
+  // https://bugs.chromium.org/p/chromium/issues/detail?id=877132
+  MinRuntimeFlag$UpdateHoverAtBeginFrame = 77, // #update-hover-at-begin-frame is enabled by default
   MinChromeFavicon2 = 77, // tested on 77.0.3865.90, chrome://favicon2/ is forbidden to use on extension pages
   // https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/h-JwMiPUnuU/sl79aLoLBQAJ
   // https://www.chromestatus.com/features/4507242028072960