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/* eslint-env mozilla/frame-script */
(function () {
addEventListener(
"load",
() => {
if (!content.location.pathname.endsWith("target.html")) {
return;
}
/**
* When a page is loaded, we expect a search string to be
* appended with the "starting time" (in ms) of when the tab
* was opened.
*
* Example: target.html?1457063506846
*/
let opened = parseInt(content.location.search.substring(1), 10);
addEventListener("MozAfterPaint", function onPaint(e) {
// for "empty" paints, where nothing has actually been
// painted. We can detect that by looking at the rect
// for the region that has painted.
let rect = e.boundingClientRect;
if (!rect.width && !rect.height) {
return;
}
removeEventListener("MozAfterPaint", onPaint);
// The MozAfterPaint event comes with a paintTimeStamp
// which tells us when in this content's lifetime the
// paint actually occurred. Note that this is not a
// measurement of when this paint occurred from
// the UNIX epoch. This makes it a little tricky to
// calculate when the paint actually occurred relative
// to the starting time that's been appended to the
// page's URL.
//
// Thankfully, the PerformanceTiming API gives us a
// sense of when this page's lifetime started, relative
// to the UNIX epoch - the "fetchStart". Taking that
// time and adding the paintTimeStamp should give us
// a pretty decent approximation of when since the
// UNIX epoch the paint actually occurred for this
// content.
//
// We can then subtract the starting time to get the
// delta, which should now represent the time it took
// from requesting that the tab be opened, to the
// paint occurring within the tab.
let fetchStart = content.performance.timing.fetchStart;
let presented = fetchStart + e.paintTimeStamp;
let delta = presented - opened;
sendAsyncMessage("TabPaint:Painted", { delta });
});
},
true
);
addEventListener(
"TabPaint:Ping",
() => {
let evt = new content.CustomEvent("TabPaint:Pong", { bubbles: true });
content.dispatchEvent(evt);
},
false,
true
);
addEventListener(
"TabPaint:Go",
e => {
sendAsyncMessage("TabPaint:Go", { target: e.detail.target });
},
false,
true
);
addMessageListener("TabPaint:OpenFromContent", () => {
let evt = new content.CustomEvent("TabPaint:OpenFromContent", {
bubbles: true,
});
content.dispatchEvent(evt);
});
addMessageListener("TabPaint:FinalResults", msg => {
let evt = Cu.cloneInto(
{
bubbles: true,
detail: msg.data,
},
content
);
content.dispatchEvent(
new content.CustomEvent("TabPaint:FinalResults", evt)
);
});
})();