[SpaghettiCthulu]

> Is the origin meaningful?

I assume no.

> What are the units

Arbitrary. The website says pixels, but the demo lets you zoom in and out, so I think defining the unit as pixels is pretty meaningless, except as a hint to the viewer of the initial scale for the canvas. Even then I can see good reasons for a viewer program to just ignore that and use whatever initial scale allows everything to fit on screen.

> how does this interact with font sizes?

Seems like the font size can't be changed, but I'd imagine it's a specific number of units.

> High-DPI displays?

Not sure what kind of answer you're looking for here. You can just scale everything, so support for High-DPI displays would be up to the viewer program.

[gcr]

I know this isn’t intended as a document presentation format, but for a consistent layout, it would be a good idea to specify the ratio between pixels (for layout) and font size (in pt). Otherwise, viewers would render text inconsistently-each node would be some ratio too big or too small for its contents.