[Webkit-unassigned] [Bug 64546] New: Redrawing dirty parts of a large table is very slow

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=64546

           Summary: Redrawing dirty parts of a large table is very slow
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: pdr at google.com


Created an attachment (id=100837)
 --> (https://bugs.webkit.org/attachment.cgi?id=100837&action=review)
Test case of slow table rendering

In a spreadsheet application we hit a performance issue when moving an absolutely positioned div over a large table. The time to redraw the dirty area of the table takes longer for larger tables, and even moderately sized tables of a few hundred rows will have unacceptably bad lag when a box is moved over top of it.

I created a small test case (see attached) displaying this issue:
On the left is a 10,000 row table, and on the right is 1,000 tables with 10 rows each. Moving the mouse over the left table, the box will lag by ~1s but moving it over the right table(s) is instantaneous.

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