React: Saved state updates the DOM but not the console - reactjs

Question

When I click, I set the saveMouseDown state to 1, when I release I set it to 0.
When I click and move the mouse I log out mouseDown and it's 0 even when my mouse is down? Yet on the screen it shows 1
import React, { useEffect, useRef, useState } from 'react';
const Home: React.FC = () => {
const [mouseDown, saveMouseDown] = useState(0);
const [canvasWidth, saveCanvasWidth] = useState(window.innerWidth);
const [canvasHeight, saveCanvasHeight] = useState(window.innerHeight);
const canvasRef = useRef<HTMLCanvasElement>(null);
let canvas: HTMLCanvasElement;
let ctx: CanvasRenderingContext2D | null;
const addEventListeners = () => {
canvas.addEventListener('mousedown', (e) => { toggleMouseDown(); }, true);
canvas.addEventListener('mouseup', (e) => { toggleMouseUp(); }, true);
};
const toggleMouseDown = () => saveMouseDown(1);
const toggleMouseUp = () => saveMouseDown(0);
const printMouse = () => console.log(mouseDown);
// ^------ Why does this print the number 1 and the 2x 0 and then 1... and not just 1?
const removeEventListeners = () => {
canvas.removeEventListener('mousedown', toggleMouseDown);
canvas.removeEventListener('mouseup', toggleMouseUp);
};
useEffect(() => {
if (canvasRef.current) {
canvas = canvasRef.current;
ctx = canvas.getContext('2d');
addEventListeners();
}
return () => removeEventListeners();
}, []);
useEffect(() => {
if (canvasRef.current) {
canvas = canvasRef.current;
canvas.addEventListener('mousemove', (e) => { printMouse(); }, true );
}
return () => canvas.removeEventListener('mousemove', printMouse);
}, [mouseDown, printMouse]);
return (
<React.Fragment>
<p>Mouse Down: {mouseDown}</p>
{/* ^------ When this does print 1? */}
<canvas
id='canvas'
ref={canvasRef}
width={canvasWidth}
height={canvasHeight}
/>
</React.Fragment>
);
};
export { Home };

Answer 1

You only add the move listener once when the component mounted, thus enclosing the initial mouseDown value.
Try using a second useEffect hook to specifically set/update the onMouseMove event listener when the mouseDown state changes. The remove eventListener needs to specify the same callback.
useEffect(() => {
if (canvasRef.current) {
canvas = canvasRef.current;
canvas.addEventListener('mousemove', printMouse, true );
}
return () => canvas.removeEventListener('mousemove', printMouse);;
}, [mouseDown, printMouse]);
It may be simpler to attach the event listeners directly on the canvas element, then you don't need to worry about working with enclosed stale state as much with the effect hooks.
<canvas
onMouseDown={() => setMouseDown(1)}
onMouseUp={() => setMouseDown(0)}
onMouseMove={printMouse}
width={canvasWidth}
height={canvasHeight}
/>