Drawing only part of an element (cropping)

[foolip]

In whatwg/html#11588 @Kaiido asked:

Was it explored whether it should get all the cropping options that drawImage has?

In other words, should we support the 9-argument variant that is explained with an image in https://html.spec.whatwg.org/multipage/canvas.html#drawing-images?

If we do this, we'd also need to support the same remapping in hit test regions.

@Kaiido is there a use case you have in mind, or are you just asking out of curiosity?

[Kaiido]

It was indeed more out of curiosity than for any actual use case, but it did happen a few times over the years I was thankful to have all these clipping options in drawImage, so I guess it could also come handy sometimes in drawHTMLElement. But I don't have no strong opinion on that. It can all be done with actual clip() and layers once we get them.

[schenney-chromium]

When it comes to implementing a src rect argument, the net result would be adding a clip with pretty much the same result as manually adding one in the canvas. So there's not a very strong performance argument to how we support clipping the HTML content.

But I do think that developers would expect an API that looks like the drawImage api, which argues for including the src rect version.