Hi,
This has been discussed briefly on public-web-perf
https://lists.w3.org/Archives/Public/public-web-perf/2015Mar/0009.html
When we measure an app's performance, we want to measure what a user
actually sees. For example when we insert something to the DOM and place
a performance marker; The marker does not reflect the timing when the
user observes the update but only reflects the timing when the DOM
operation is finished.
This is crucial to get realistic performance measurement. We often could
only use high speed camera but it's not widely available.
I think I could explain what I want in this simple example:
// do the work to update DOM
performance.delayedMark('drawn', 'visuallyLoaded');
The UA should add the marker when modifications up to that point have
been drawn onto the screen.
We cannot simply use rAF because it could change the performance
characteristic and we can't easily correlate a frame to our js code.
Combining rAF and frame timing API might achieve what we want but
frame timing API only reports "slow-frame" now; it also cannot avoid the
use of rAF.
Do you think this API makes sense? Would it be very hard to implement in
gecko?
Kanru
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