I need to specify any possible size, this becomes super critical stable layout on the page.
I guess what you are trying to determine here is if we could have a custom post processing job that injects size into the HTML and takes this decision away from the user.
My answer to this would be … maybe… If you upload retina you want to specify the smaller size so the retina screens get high fidelity and non-retina just get scaled down. It is possible we could glue this information into an EXIF tag or something and then have a post processor magic an SRCSET. But it would be a huge change.
line breaks between
We absolutely need to deal with this cause we have tons of history, I can hack
html_block.js to support this edge condition quite easily. But I also think the spec needs an adjustment here.
sepecifying custom image size
I also think the spec should deal with this, especially cause of the HiDPI concern.