My code is:

var canvas = document.getElementById("canvas");
ctx = canvas.getContext("2d");
ctx.canvas.width = 40vw;
ctx.canvas.height = 40vh;

and it doesn't work. Is it possible to use vw and vh when setting canvas dimensions in JavaScript? If so, how?

My code is:

var canvas = document.getElementById("canvas");
ctx = canvas.getContext("2d");
ctx.canvas.width = 40vw;
ctx.canvas.height = 40vh;

and it doesn't work. Is it possible to use vw and vh when setting canvas dimensions in JavaScript? If so, how?

• javascript
• html
• html5-canvas

Share Improve this question Follow asked Oct 17, 2015 at 21:43 JonahJonah 1,54544 gold badges1717 silver badges3434 bronze badges 4

• 1 Possible duplicate of stackoverflow./questions/1664785/… – andyderuyter Commented Oct 17, 2015 at 21:46
• You should set the number of pixels with width and height attributes, whose value is an integer. Then, you can distort it with CSS. – Oriol Commented Oct 17, 2015 at 21:57
• @Oriol That just stretches the image for me. How can I go about setting the width and height attributes as proportions of the view port? – Jonah Commented Oct 17, 2015 at 22:10
• @Oriol Never mind, just realised I can easily use document.documentElement.clientWidth and document.documentElement.clientHeight instead of using vw/vh – Jonah Commented Oct 17, 2015 at 22:12

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2 Answers 2

Sorted by: Reset to default 3

I realised I could use document.documentElement.clientWidth and document.documentElement.clientHeight to work out the vw and vh respectively.

HTML:

<canvas class="canvas_hangman"></canvas> 

JS:

function setUpCanvas() {
  canvas = document.getElementsByClassName("canvas_hangman")[0];
  ctx = canvas.getContext('2d');
  ctx.translate(0.5, 0.5);

  // Set display size (vw/vh).
  var sizeWidth = 80 * window.innerWidth / 100,
    sizeHeight = 100 * window.innerHeight / 100 || 766;

  //Setting the canvas site and width to be responsive 
  canvas.width = sizeWidth;
  canvas.height = sizeHeight;
  canvas.style.width = sizeWidth;
  canvas.style.height = sizeHeight;
}

window.onload = setUpCanvas();

This perfectly sets up your HTML canvas to draw on, in a responsive manner too.