Re: [css-display]? Compositing, expensive things, and laziness

> [...] rendering events [...]

While I'm not an implementor myself, I don't think any implementor is ready 
to accept the idea of such rendering-fallback events. Triggering a 
rendering-fallback event in order to show a placeholder requires making a 
junction to a JS function running on the main thread before terminating the 
rendering phase. It doesn't seem to me any vendor will be okay to pay that 
price.

A "::waiting-rendering" pseudo-element (that could be used by the browser in 
place of the contents to show a placeholder (for example in the form of an 
inlined data-uri SVG)) is probably a more acceptable proposal.