510120 - Show cached images while waiting for if-modified-since responses

Status: RESOLVED INVALID

(Core :: Graphics: ImageLib, enhancement)

Description

[Jesse Ruderman]

It might be good to show cached images while waiting for if-modified-since responses.

This could speed up the useful display of web pages, especially on slow connections, in two ways.  First, images would be shown sooner.  Second, the if-modified-since request could be made lower priority compared to other pieces of the page, perhaps even delayed until the rest of the page has loaded completely.

Note that this wouldn't change the semantics of when if-modified-since requests are required, and would not change the final display of the page.  We'd want to not fire onload for the image or the page -- similarly to images loading incrementally.

Questions:

* For images, how common are (1) use of cache without sending an if-modified-since request, (2) "304 not modified", (3) 200 without modifications, and (4) 200 with modifications?

* What is the cost of what might be an extra disk fetch and image decode?

Comment 1

[Doug Sherk (:drs) (inactive)]

Personally I disagree that we should do this as users could be given false information, even if it's for a very short time. Other issues: what happens if you stop the page refresh while it's fetching the new images? If the cached images go away, it's bad UX, but if they stay, then the user has wrong data.

I'm closing this as part of the gfx bugkill (not because I disagree with doing it). Please re-open if you still want to discuss this or anyone wants to try implementing it.