1773020 - understand why bug 1231622 caused a drawing regression and bug 1769195 fixed it

Status: NEW

(Core :: Web Painting, defect, P3)

Description

[Timothy Nikkel (:tnikkel)]

In looking at the facebook-nav.marketplace LastVisualChange regression caused by bug 1769195 (and bug 1231622 before it causing an equal improvment) linked here https://bugzilla.mozilla.org/show_bug.cgi?id=1769195#c9 I noticed that the icon in the chat bubble at bottom right is never drawn after bug 1231622 but before bug 1769195. This does not make sense, there should be no drawing regression caused by bug 1231622, and bug 1769195 should not fix a drawing regression.

The drawing regression is reproducible on try on linux and mac, but I have not been able to reproduce it on mac, windows nor linux.

This bug is to understand what is going on here. There's likely still a bug here, just bug 1769195 is masking it or making it less likely to appear.

Comment 1

[Timothy Nikkel (:tnikkel)]

I think I understand this now. There was never a drawing regression. The bug that I was observing was a bug with collecting profiler screenshots. The profiler screenshots are queued, and the one from the previous frame is submitted after the next frame. Which means that the last frame generated by a page load will sit in the queue and not get submitted and not show up in the profile. The last frame of the page in question was the only one with the chat icon in it, so it appeared as though the chat icon never showed up when in reality we just failed to grab the last screenshot with the icon in it. I verified this by creating a timer to submit any pending screenshots if they don't get submitted.

Comment 2

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:tnikkel, could you have a look please?

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