Value
A number equal to the number of CSS pixels from the top edge of the browser viewport to the top edge of the screen.
Examples
In our screenleft-screentop example, you'll see a canvas onto which has been drawn a circle. In this example we are using Window.screenLeft/Window.screenTop plus Window.requestAnimationFrame() to constantly redraw the circle in the same physical position on the screen, even if the window position is moved.
js
initialLeft = window.screenLeft + canvasElem.offsetLeft;
initialTop = window.screenTop + canvasElem.offsetTop;
function positionElem() {
let newLeft = window.screenLeft + canvasElem.offsetLeft;
let newTop = window.screenTop + canvasElem.offsetTop;
let leftUpdate = initialLeft - newLeft;
let topUpdate = initialTop - newTop;
ctx.fillStyle = "rgb(0 0 0)";
ctx.fillRect(0, 0, width, height);
ctx.fillStyle = "rgb(0 0 255)";
ctx.beginPath();
ctx.arc(
leftUpdate + width / 2,
topUpdate + height / 2 + 35,
50,
degToRad(0),
degToRad(360),
false,
);
ctx.fill();
pElem.textContent = `Window.screenLeft: ${window.screenLeft}, Window.screenTop: ${window.screenTop}`;
window.requestAnimationFrame(positionElem);
}
window.requestAnimationFrame(positionElem);
These work in exactly the same way as screenX/screenY.
Also in the code we include a snippet that detects whether screenLeft is supported, and if not, polyfills in screenLeft/screenTop using screenX/screenY.
js
if (!window.screenLeft) {
window.screenLeft = window.screenX;
window.screenTop = window.screenY;
}
Specifications
| Specification |
|---|
| CSSOM View Module # dom-window-screeny |