blob: 25aca45f79d317596e52eb997bcb532f4abd552c [file] [log] [blame]
const scheduler = new class
{
constructor()
{
this._frameID = -1;
this._layoutCallbacks = new Set;
}
// Public
get hasScheduledLayoutCallbacks()
{
return this._frameID !== -1 || this._layoutCallbacks.size > 0;
}
scheduleLayout(callback)
{
if (typeof callback !== "function")
return;
this._layoutCallbacks.add(callback);
this._requestFrameIfNeeded();
}
unscheduleLayout(callback)
{
if (typeof callback !== "function")
return;
this._layoutCallbacks.delete(callback);
}
flushScheduledLayoutCallbacks()
{
this._frameDidFire();
}
// Private
_requestFrameIfNeeded()
{
if (this._frameID === -1 && this._layoutCallbacks.size > 0)
this._frameID = window.requestAnimationFrame(this._frameDidFire.bind(this));
}
_frameDidFire()
{
if (typeof scheduler.frameWillFire === "function")
scheduler.frameWillFire();
this._layout();
this._frameID = -1;
this._requestFrameIfNeeded();
if (typeof scheduler.frameDidFire === "function")
scheduler.frameDidFire();
}
_layout()
{
// Layouts are not re-entrant.
const layoutCallbacks = this._layoutCallbacks;
this._layoutCallbacks = new Set;
for (let callback of layoutCallbacks)
callback();
}
};