Is broadway backend ignoring GDK_SCALE and/or GDK_DPI_SCALE ?

[Andrea Giammarchi <andrea giammarchi gmail com>]

Hello there,

  I wonder if there's any chance I can have "broadway canvas" showing HiDPi UI.

The current result is shown in this gist:

https://gist.github.com/WebReflection/93f58c8b7ac986eb7960

The canvas, in this case, draws 384px width image on a 384px width canvas, but on HiDPi I'd expect to see 768px width image on 384px canvas, something like the following:

```html

<canvas

  width="768" height="858"

  style="width: 384px; height: 429px; position: absolute; left: 100px; top: 100px; display: inline; visibility: visible; z-index: 0;"

></canvas>

```

In few words, I wonder if the drawing and other events should use `window.devicePixelRatio` as multiply factor in order to show sharp images on HiDPi screens.

Apologies if this is not the right ML or I'm missing some basic command/env variable, I've tried to search but nothing came up.

Thanks and Best Regards