[Webkit-unassigned] [Bug 193239] New: [GTK][WPE] Graphic issue with invalidations on composited layers with subpixel positions

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=193239

            Bug ID: 193239
           Summary: [GTK][WPE] Graphic issue with invalidations on
                    composited layers with subpixel positions
           Product: WebKit
           Version: WebKit Local Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebKit2
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: karl.leplat_ext at softathome.com
                CC: achristensen at apple.com, bfulgham at webkit.org,
                    cgarcia at igalia.com, ews at webkit.org, fred.wang at free.fr,
                    hyatt at apple.com, loic.yhuel at softathome.com,
                    magomez at igalia.com, mcatanzaro at igalia.com,
                    olivier.blin at softathome.com, rniwa at webkit.org,
                    simon.fraser at apple.com, zalan at apple.com,
                    zan at falconsigh.net

Created attachment 358598

  --> https://bugs.webkit.org/attachment.cgi?id=358598&action=review

Patch

3 In compositing mode, rendering artifacts have been detected on the repaint of elements on subpixel position.
  4 We suspect a problem on rounding when rects are invalidated in the backing store, this bug is reproducible on WebKit GTK and WPE.
  5 This bug is not reproducible with compositing mode disabled.
  6 
  7 Graphic layer positons for this layoutTest :
  8                         invalidate/repaint rect
  9 ------------20px           ------------21px rounded from 20,796875px
 10 -    32px  -               -    31px  - missing 1px of height ??
 11 ------------52px    ---->  ------------ 
 12 -    33px  -
 13 ------------84px
 14 -    32px  -
 15 ------------

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