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function delayByFrames(f, num_frames) {
function recurse(depth) {
if (depth == 0)
f();
else
requestAnimationFrame(() => recurse(depth-1));
}
recurse(num_frames);
}
// Returns a Promise which is resolved with the event object when the event is
// fired.
function getEvent(eventType) {
return new Promise(resolve => {
document.body.addEventListener(eventType, e => resolve(e), {once: true});
});
}
// Returns a Promise which is resolved with a "true" iff transient activation
// was available and successfully consumed.
//
// This function relies on Fullscreen API to check/consume user activation
// state.
async function consumeTransientActivation() {
try {
await document.body.requestFullscreen();
await document.exitFullscreen();
return true;
} catch(e) {
return false;
}
}
function receiveMessage(type) {
return new Promise((resolve) => {
window.addEventListener("message", function listener(event) {
if (typeof event.data !== "string") {
return;
}
const data = JSON.parse(event.data);
if (data.type === type) {
window.removeEventListener("message", listener);
resolve(data);
}
});
});
}