apple2js/js/components/CPUMeter.tsx

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import { h } from 'preact';
import { useCallback, useEffect, useRef, useState } from 'preact/hooks';
import { Apple2 as Apple2Impl } from '../apple2';
import type { Stats } from '../apple2';
import styles from './css/CPUMeter.module.scss';
/**
* Interface for CPUMeter.
*/
export interface CPUMeterProps {
apple2: Apple2Impl | undefined;
}
/**
* A simple display that can cycle between emulator Khz
* performance, frames/second and rendered frames/second.
*
* @param apple2 Apple2 object
* @returns CPU Meter component
*/
export const CPUMeter = ({ apple2 }: CPUMeterProps) => {
const lastStats = useRef<Stats>({
frames: 0,
renderedFrames: 0,
cycles: 0,
});
const lastTime = useRef<number>(Date.now());
const [khz, setKhz] = useState<number>(0);
const [fps, setFps] = useState<number>(0);
const [rps, setRps] = useState<number>(0);
const [mode, setMode] = useState<number>(0);
useEffect(() => {
const interval = setInterval(() => {
const { cycles, frames, renderedFrames } = lastStats.current;
const stats = apple2?.getStats();
const time = Date.now();
const delta = time - lastTime.current;
if (stats) {
setKhz(
Math.floor(
(stats.cycles - cycles) / delta
)
);
setFps(
Math.floor(
(stats.frames - frames) / delta * 1000
)
);
setRps(
Math.floor(
(stats.renderedFrames - renderedFrames) / delta * 1000
)
);
lastStats.current = { ...stats };
lastTime.current = time;
}
}, 1000);
return () => clearInterval(interval);
}, [apple2]);
const onClick = useCallback(() => {
setMode((mode) => (mode + 1) % 3);
}, []);
return (
<div className={styles.khz} onClick={onClick}>
{mode === 0 && `${khz} Khz`}
{mode === 1 && `${fps} fps`}
{mode === 2 && `${rps} rps`}
</div>
);
};