1220798 - Optimize Top Site Thumbnail cell layout and configuration to be more performant

Status: RESOLVED FIXED

(Firefox for iOS :: Home screen, defect)

Description

[Stephan Leroux [:sleroux]]

Profiling the Top Sites code reveals that although the query we're making for the top sites data is ~400ms (see https://bugzilla.mozilla.org/show_bug.cgi?id=1211984), the work we do on the main thread for layout is also quite long (~200 ms). 

There seems to be two factors in the sluggishness of the UI:

1. Applying the blur on the favicon image on the main thread takes ~50ms.
2. SnapKit constraint setup and subview complexity a significant amount of time as well.

Some solutions:

1. Only calculate blurred version of favicon once and cache... We already cache favicons so it shouldn't be too bad, we would just need to add more invalidation logic
2. Simplify the views for the thumbnail cell as much as we can. I'm not sure if it's just that SnapKit is slow or auto layout but some investigation into this is needed.

Comment 1

[Stephan Leroux [:sleroux]]

Attachment: aauws9o9QZogrrzCV68lX3ih4ROi39G5rTO7qDClbPw.png

Profile w/o cache optimization

Comment 2

[Stephan Leroux [:sleroux]]

Moved the blurring story into it's own bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1221118

Comment 3

[Richard Newman [:rnewman]]

This'll do.