canvas-input-range v0.3.8

HTML Canvas range input.

Tiny, fast and easy to use range input based on HTML canvas 2D rendering context with 0 runtime dependency. This project is very young and has not been tested on a wide range of browsers yet.

Usage

Steps

1. Install with

npm instal --save canvas-input-range

Or just load it from a CDN.

2. Define a container for the range input, which will automatically fill it and adapt to horizontal or vertical orientation using its parent aspect ratio.
3. Define a callback function, which will be invoked on every value change.
4. Load the rail and knob images. Both of them must have uniform scales (they must be drawn inside a square view port) and must have the same size. The rail will be scaled up to fill the parent element, therefore if it is an SVG (recommended) its preserveAspectRatio attribute must be set to "none".
5. Call the range.init function after your images are loaded.

Notes

• This library doesn't ship an image loader function, because one of your dependencies already does, if not, just borrow mine from the example.
• value of the range changes between 0 and 1.

Example

// Container element of the range input
var rangeBox = document.getElementById("range-box");
// The element where the input range value will be written
var valueBox = document.getElementById("value-box");

// Simple image loader function which returns a promise
function loadImg(path) {
	const img = document.createElement("img");
  const prom = new Promise((resolve, reject) => {
    img.onload = () => resolve(img);
    img.onerror = (err) => reject(err);
  });
  img.src = path;
  return prom;
}

// Callback executed on every value change.
function cb(val) {
  valueBox.innerHTML = val
}

// Load rail.svg and knob.svg than init range input
Promise.all([loadImg("rail.svg"), loadImg("knob.svg")])
    .then((imgArr) => {
      range.init(
        rangeBox, // parent element
        cb, // callback
        imgArr[0], // rail image
        imgArr[1], // knob image
      );
});

Full working example on Glitch.

Extra features

• Set initial value. When you call range.init it will return a function which can be used to set the value, hence the position of the range.
• You can override the rail and knob repaint events. Please check the example in the demo directory.

Hints

• Set user-select CSS property to none for your gui elements in general to prevent users from accidentally selecting them.
• If you have trouble making the rail and knob images, use mine from the glitch example or from the demo directory.

Milestones

• Accessibility keyboard control.