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CanvasRenderingContext2D: drawFocusIfNeeded() method

The CanvasRenderingContext2D.drawFocusIfNeeded() method of the Canvas 2D API draws a focus ring around the current or given path, if the specified element is focused.

Syntax

js

drawFocusIfNeeded(element)
drawFocusIfNeeded(path, element)

Parameters

element

The element to check whether it is focused or not.

path

A Path2D path to use.

Return value

None (undefined).

Examples

Managing button focus

This example draws two buttons on a canvas. The drawFocusIfNeeded() method is used to draw a focus ring when appropriate.

HTML

html

<canvas id="canvas">
  <button id="button1">Continue</button>
  <button id="button2">Quit</button>
</canvas>

JavaScript

js

const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
const button1 = document.getElementById("button1");
const button2 = document.getElementById("button2");

document.addEventListener("focus", redraw, true);
document.addEventListener("blur", redraw, true);
canvas.addEventListener("click", handleClick, false);
redraw();

function redraw() {
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  drawButton(button1, 20, 20);
  drawButton(button2, 20, 80);
}

function handleClick(e) {
  // Calculate click coordinates
  const x = e.clientX - canvas.offsetLeft;
  const y = e.clientY - canvas.offsetTop;

  // Focus button1, if appropriate
  drawButton(button1, 20, 20);
  if (ctx.isPointInPath(x, y)) {
    button1.focus();
  }

  // Focus button2, if appropriate
  drawButton(button2, 20, 80);
  if (ctx.isPointInPath(x, y)) {
    button2.focus();
  }
}

function drawButton(el, x, y) {
  const active = document.activeElement === el;
  const width = 150;
  const height = 40;

  // Button background
  ctx.fillStyle = active ? "pink" : "lightgray";
  ctx.fillRect(x, y, width, height);

  // Button text
  ctx.font = "15px sans-serif";
  ctx.textAlign = "center";
  ctx.textBaseline = "middle";
  ctx.fillStyle = active ? "blue" : "black";
  ctx.fillText(el.textContent, x + width / 2, y + height / 2);

  // Define clickable area
  ctx.beginPath();
  ctx.rect(x, y, width, height);

  // Draw focus ring, if appropriate
  ctx.drawFocusIfNeeded(el);
}

Result

Specifications

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
drawFocusIfNeeded 37 14 3228 No 24 8 37 37 3228 24 8 3.0
path_parameter 37 14 No No 24 8 37 37 No 24 8 3.0

See also

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Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/CanvasRenderingContext2D/drawFocusIfNeeded