@nativescript/core/fps-meter/index.js

A JavaScript library providing an easy to use api for interacting with iOS and Android platform APIs.

import * as fpsNative from './fps-native';
const callbacks = {};
let idCounter = 0;
let _minFps = 1000;
let framesRendered = 0;
let frameStartTime = 0;
function doFrame(currentTimeMillis) {
    let fps = 0;
    if (frameStartTime > 0) {
        // take the span in milliseconds
        const timeSpan = currentTimeMillis - frameStartTime;
        framesRendered++;
        if (timeSpan > 1000) {
            fps = (framesRendered * 1000) / timeSpan;
            if (fps < _minFps) {
                _minFps = fps;
            }
            notify(fps);
            frameStartTime = currentTimeMillis;
            framesRendered = 0;
        }
    }
    else {
        frameStartTime = currentTimeMillis;
    }
}
let native;
function ensureNative() {
    if (!native) {
        native = new fpsNative.FPSCallback(doFrame);
    }
}
export function reset() {
    _minFps = 1000;
    frameStartTime = 0;
    framesRendered = 0;
}
export function running() {
    if (!native) {
        return false;
    }
    return native.running;
}
export function minFps() {
    return _minFps;
}
export function start() {
    ensureNative();
    native.start();
}
export function stop() {
    if (!native) {
        return;
    }
    native.stop();
    reset();
}
export function addCallback(callback) {
    const id = idCounter;
    // Wrap all calback in zonedCallback so that they work with the current zone.
    callbacks[id] = zonedCallback(callback);
    idCounter++;
    return id;
}
export function removeCallback(id) {
    if (id in callbacks) {
        delete callbacks[id];
    }
}
function notify(fps) {
    let callback;
    for (const id in callbacks) {
        callback = callbacks[id];
        callback(fps, _minFps);
    }
}
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