> there is no real reason why render time should scale at all with content hidden below the fold
The reason is that CSS layout is exceedingly complex and all of the elements within or even across container boundaries can influence the position and appearance of other elements.
If they did their own custom layout using absolute positioning + JavaScript, then they could easily create "virtualize" the items in the container, only rendering those that are currently visible.
This is a major reason that I'm a believer in the React.js or other "Immediate Mode UI" models. This is how games have worked forever: You simply query your world state for "stuff currently in view" and draw that as fast as you can, caching anything that change infrequently and is expensive to recompute.
Yeah. I think with the move towards heavy client side apps, things like Reacts model will become the way to go. Possibly even implemented on Canvas... but that's likely a while off.
The reason is that CSS layout is exceedingly complex and all of the elements within or even across container boundaries can influence the position and appearance of other elements.
If they did their own custom layout using absolute positioning + JavaScript, then they could easily create "virtualize" the items in the container, only rendering those that are currently visible.
This is a major reason that I'm a believer in the React.js or other "Immediate Mode UI" models. This is how games have worked forever: You simply query your world state for "stuff currently in view" and draw that as fast as you can, caching anything that change infrequently and is expensive to recompute.