[geometry-1] DOMMatrixInit is not too useful if a DOMMatrix constructor cannot accept such a value

[trusktr]

You'd think this should be possible:

const init = {m11: 1, ..., m44: 1}

const matrix = new DOMMatrix(init)

Instead, one has to do this:

const init = {m11: 1, ..., m44: 1}

const matrix = new DOMMatrix([init.m11, ..., init.m44])

which is more cumbersome and also more wasteful (an extra array is created just to create a new DOMMatrix), or this:

const init = {m11: 1, ..., m44: 1}

const matrix = Object.assign(new DOMMatrix(), init)

which is also not as simple as it could be.

These problems could be alleviated if toFloat32Array or toFloat64Array methods would accept a target array to write to, making it easy to clone matrices without allocating new arrays:

const array = new Float32Array(16)

matrix.toFloat32Array(array) // provide an array to write to (instead of it creating a new one)

const newMatrix = new DOMMatrix(array)

(to this end, it should also just have toArray to return (or write to) a regular array)