REGRESSION (r232356): After zooming a page in and out, it's possible to temporarily have missing tiles (google.com, apple.com)

[Antti Koivisto]

We ignore zoom scale from UI process if it doesn't match the last remote layer tree transaction. However nothing guarantees that we receive the real scale again until user interacts with the page. After r232356 this can cause visibly missing tiles, before the problem was covered by creating too many of them.

[Antti Koivisto]

<rdar://problem/30404627>

[Antti Koivisto]

I mean <rdar://problem/41863803>

[Antti Koivisto]

Created attachment 344839 [details]
patch

[Simon Fraser (smfr)]

Comment on attachment 344839 [details]
patch

View in context: https://bugs.webkit.org/attachment.cgi?id=344839&action=review

> Source/WebKit/WebProcess/WebPage/WebPage.h:1669
> +    float m_lastTransactionPageScaleFactor { 0 };

We store page scale as a double in RemoteLayerTreeTransaction and we've certainly had bugs with float/double precision mismatch before, so should this be a double, and/or do matching with epsilon?

> Source/WebKit/WebProcess/WebPage/WebPage.h:1670
> +    uint64_t m_lastTransactionIDWithScaleChange { 0 };

I wish we had a typedef for transactionIDs :(

[Antti Koivisto]

Created attachment 344865 [details]
patch

[WebKit Commit Bot]

Comment on attachment 344865 [details]
patch

Clearing flags on attachment: 344865

Committed r233780: <https://trac.webkit.org/changeset/233780>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.