Should x and y arguments be optional?

[foolip]

The w and h arguments are already optional, defaulting to the width and height of the layout box. Should we do the same thing for x and y, defaulting to the position of the layout box?

This could be convenient if elements are positioned using CSS relative to one another, and one simply wants to make them appear on the canvas in the right positions.

[Kaiido]

Oh, I expected 0, 0 to behave like this by default. I now see that indeed all of position, transform, and margin are discarded... That's quite surprising.

I believe most users would indeed expect that ctx.drawHTMLElement(elem, 0, 0, canvas.width, canvas.height) will just render the element exactly as if it was in the usual layout tree. For the, I think, more rare case where one would want its margins or positioning to be discarded, they could just not set it in their CSS, or control the position from getBoundingClientRect().

[foolip]

@progers @schenney-chromium thoughts?

[Kaiido]

Thinking about it a bit more, I guess what I expected could also be achieved by drawing a wrapper with width:100%; height: 100%.

[schenney-chromium]

Should we make x and y optional I guess the HTML content would be drawn relative to the canvas parent position. I's well defined I believe. I think we would still want to discard transform, however, because I suspect it might be more confusing to use the transform WRT the canvas itself.

[foolip]

I've tried this out a bit in Chrome Canary, and positioning the children with CSS is actually very hard. I couldn't get them to be positioned anywhere except at (0, 0) with any combination of position: relative and position: absolute. Also, since each child is laid out independently (as if it was the only child) you can't really build a layout that you then "just draw" in the way I was imagining.

So unless there's some way to infer x and y that would be useful, let's not make them optional :)