Deprecating the unload event

[Garnet-Fox]

Good day.
There is an "unload" event in the source code, chromium browsers are already complaining about it. Currently, I noticed that on mobile devices like chromium, unload does not fire or does not always fire, the return cache does not work correctly.
What is the correct way to replace it with “pagehide” or “beforeunload” or "visibilitychange"?
Google Deprecating the unload event

[Garnet-Fox]

I made a small fix because it’s urgent, it might be useful to someone. Do not judge strictly.
The "beforeunload" event seems to correctly calc the scrolling, but the scrolling itself is visible - unfortunately.
Event "pagehide" - failed to make friends with Safari, i.e. For the Chromium line everything is great, but in Safari the scroll calculation fails the first time you go back.
I've settled on "visibilitychange" for now, no critical bugs seem to be visible, currently browser support is 95%.
Instead of lines:
window[ addRemove ]( 'unload', this.unloadHandler );
Fix:
var _this = this;
function fix(e) {
if (document.visibilityState === "hidden") {
_this.unloadHandler.call(document, e);
}
}
document[ addRemove ]( 'visibilitychange', fix);

[cihankaracom]

I notice this problem for years. I decided to fix it. So i did it in this way:

First of all, use unminified version of js, after fixing minify it again.

Replace "proto.onUnload = function" function with this function:

proto.onVisibilityChange = function() {
  if (!this.scrollPage) return;
  if (this.scrollPage.top === 0) return;
  if (document.visibilityState === 'visible') return;

  // calculate where scroll position would be on refresh
  let scrollY = window.scrollY - this.scrollPage.top + this.top;
  // disable scroll event before setting scroll #679
  this.destroyHistory();
  scrollTo(0, scrollY);
};

also add this function below this function:

proto.bindVisibilityChangeEvent = function(isBind) {
  let addRemove = isBind ? 'addEventListener' : 'removeEventListener';
  window[addRemove]('visibilitychange', this.onVisibilityChange);
};

then find "proto.createHistoryAppend = function()" function, replace it this one:

proto.createHistoryAppend = function() {
  this.updateMeasurements();
  this.updateScroller();
  // array of scroll positions of appended pages
  this.scrollPages = [
    // first page
    {
      top: 0,
      path: location.href,
      title: document.title,
    },
  ];
  this.scrollPage = this.scrollPages[0];
  // events
  this.scrollHistoryHandler = this.onScrollHistory.bind( this );
  this.visibilityChangeHandler = this.onVisibilityChange.bind(this);
  this.scroller.addEventListener( 'scroll', this.scrollHistoryHandler );
  this.on( 'append', this.onAppendHistory );
  this.bindHistoryAppendEvents( true );
  this.bindVisibilityChangeEvent(true);
};

finally, replace "proto.bindHistoryAppendEvents = function(isBind)" function with this one:

proto.bindHistoryAppendEvents = function(isBind) {
  let addRemove = isBind ? 'addEventListener' : 'removeEventListener';
  this.scroller[addRemove]('scroll', this.scrollHistoryHandler);
  this.bindVisibilityChangeEvent(isBind);
};

I did not encounter any problems when I made changes this way. If you encounter any problems, I would appreciate it if you let me know.

[1aurabrown]

@Garnet-Fox @cihankaracom have either of you opened a PR for these fixes?